Development in Wastewater Treatment Research and Processes: Innovative Microbe-Based Applications for Removal of Chemicals and Metals in Wastewater Treatment Plants 0323856578, 9780323856577

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Development in Wastewater Treatment Research and Processes

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Development in Wastewater Treatment Research and Processes Innovative Microbe-Based Applications for Removal of Chemicals and Metals in Wastewater Treatment Plants Edited by Maulin P. Shah Senior Environmental Microbiologist, Environmental Microbiology Lab, Bharuch, Gujarat, India

Susana Rodriguez-Couto Department of Separation Science, LUT School of Engineering Science, LUT University, Mikkeli, Finland

Riti Thapar Kapoor Assistant Professor (Grade-III), Amity Institute of Biotechnology, Amity University, Uttar Pradesh, India

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Contents Contributors.......................................................................................... xix

CHAPTER 1 A comparative study between physicochemical and biological methods for effective removal of textile dye from wastewater ............................................... 1 Subhasish Dutta and Joyani Bhattacharjee 1 2

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Introduction ...................................................................... 1 Types of dyes and their toxicity............................................ 2 2.1 Azo dyes...................................................................3 2.2 Acid dye ...................................................................4 2.3 Basic dye ..................................................................4 2.4 Direct dye .................................................................4 2.5 Vat dye .....................................................................4 Physical methods ............................................................... 4 3.1 Adsorption.................................................................5 3.2 Coagulation and flocculation.........................................7 3.3 Emerging physical method for the treatment of textile dye effluents ..............................................................8 Membrane technology......................................................... 8 4.1 Microfiltration............................................................8 4.2 Reverse osmosis .........................................................9 4.3 Nanofiltration.............................................................9 4.4 Ultrafiltration .............................................................9 Chemical methods.............................................................. 9 5.1 Fenton method ......................................................... 10 5.2 Ozonation................................................................ 10 5.3 Cucurbitiril .............................................................. 11 5.4 Sodium hypochlorite ................................................. 11 5.5 Recent biochemical trend ........................................... 12 Advanced oxidation process................................................13 Biological methods............................................................14 7.1 Degradation with bacteria........................................... 15 7.2 Degradation with algal culture .................................... 16 7.3 Degradation with yeast .............................................. 16 7.4 Degradation with fungi .............................................. 16 7.5 Degradation with white-rot fungi................................. 16 7.6 Enzyme system of white-rot fungi ............................... 17 Conclusion.......................................................................19 References .......................................................................19

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CHAPTER 2 An approach toward developing clean green techniques to deal with heavy metal toxicity using the microbiome.............................................23 Subhasish Dutta and Pitam Chakrabarti 1 2

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Introduction .....................................................................23 Different heavy metals and their impacts...............................24 2.1 Arsenic ................................................................... 24 2.2 Cadmium ................................................................ 25 2.3 Lead....................................................................... 25 2.4 Nickel..................................................................... 26 2.5 Mercury .................................................................. 26 2.6 Copper.................................................................... 26 2.7 Chromium ............................................................... 26 Bioremediation: the savior of the environment .......................28 3.1 Biosorption.............................................................. 28 3.2 Bioaugmentation: a new green technology .................... 30 3.3 Phytoremediation...................................................... 31 3.4 Mycoremediation, erasing environmental pollutants........ 32 3.5 Bioventing and biosparging ........................................ 33 3.6 Cyanoremediation..................................................... 34 3.7 Biostimulation.......................................................... 35 3.8 Bioleaching ............................................................. 36 Factors affecting bioremediation ..........................................37 4.1 Availability of nutrients ............................................. 37 4.2 Temperature............................................................. 37 4.3 pH.......................................................................... 37 Conclusion.......................................................................38 References .......................................................................38

CHAPTER 3 Microbial degradation of pesticides: microbial potential for degradation of pesticides....................41 Sangeeta Kumari, Deepak Kumar and S.M. Paul Khurana 1

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Introduction: pesticides effect on environment health ..............41 1.1 Pesticides ................................................................ 43 1.2 Classification of pesticide........................................... 43 1.3 Pesticide fate in the environment ................................. 43 Biomagnification: tenacious effect of pesticides......................47 2.1 Bioaccumulation and biomagnification ......................... 47 Microbial potential: effective degradation of pesticides............48

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Types of bioremediation technologies ...................................50 4.1 Bioremediation factors............................................... 52 Biochemical mechanism of pesticides bioremediation..............52 5.1 Inference ................................................................. 54 References .......................................................................60

CHAPTER 4 Biodegradation and photocatalysis of pharmaceuticals in wastewater ..............................69 Salman Farissi, Sneha Ramesh, Muthukumar Muthuchamy and Anbazhagi Muthukumar 1 2 3

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Introduction .....................................................................69 1.1 Pharmaceuticals........................................................ 70 Biodegradation .................................................................71 Biodegradation approaches for the treatment of pharmaceutical wastes........................................................72 3.1 Bacterial degradation................................................. 72 3.2 Fungal degradation.................................................... 73 3.3 Enzymatic degradation............................................... 74 Factors affecting the biodegradation of pharmaceuticals...........77 4.1 Photocatalysis .......................................................... 78 4.2 Process enhancement conditions.................................. 84 4.3 Recent advancements and approaches........................... 85 4.4 Photoelectrocatalytic oxidation.................................... 88 Conclusion.......................................................................92 References .......................................................................93

CHAPTER 5 Recent trends in the microbial degradation and bioremediation of emerging pollutants in wastewater treatment system .................................99 Jayshree Annamalai, Sabeela Beevi Ummalyma and Ashok Pandey 1 2

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Introduction .....................................................................99 Emerging pollutants as micropollutants............................... 100 2.1 Pharmaceuticals...................................................... 101 2.2 Pesticides .............................................................. 102 2.3 Plasticizers ............................................................ 106 2.4 Brominated flame retardants ..................................... 107 2.5 Perfluorinated compounds ........................................ 108 Fate of emerging micropollutants in aqueous environment ................................................................... 109

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Microbial degradation of micropollutants ............................ 111 4.1 Degradation pathways and metabolic residues of phthalate esters....................................................... 111 Microbial cells and their enzymes in wastewater treatment..... 112 5.1 Bacteria and fungi................................................... 114 5.2 Microalgae ............................................................ 116 Perspectives of microbial degradation and challenges ............ 117 Advancements in microbial cell-based wastewater treatment .. 117 7.1 Genetic engineering ................................................ 117 7.2 Biogenic nanoparticles............................................. 118 7.3 Integrated systems................................................... 118 Conclusion..................................................................... 119 Acknowledgment ............................................................ 119 References ..................................................................... 120

CHAPTER 6 Biological methods for textile dyes removal from wastewaters................................................. 127 Ashish Kumar Sahoo, Anjali Dahiya and Bhisma K. Patel 1

Introduction ................................................................... 127 1.1 Types of dyes......................................................... 129 1.2 Textile dyes and their impact on the environment......... 131 1.3 Methods for the treatment of textile dyes .................... 134 1.4 Biological treatment ................................................ 134 1.5 Decolorization treatment of dispersed textile dyes ........ 144 1.6 Conclusion and outlook ........................................... 145 References ..................................................................... 146

CHAPTER 7 Importance and applications of biofilm in microbe-assisted bioremediation .......................... 153 Janhavi Gadkari, Sourish Bhattacharya and Anupama Shrivastav 1 2

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Introduction ................................................................... 153 An overview of biofilm .................................................... 154 2.1 Composition of biofilms........................................... 155 2.2 Mechanism of biofilm formation ............................... 156 2.3 Factors affecting biofilm formation ............................ 157 2.4 Biofilm formed by different microbial species ............. 159 An overview of bioremediation.......................................... 161 Role of biofilm in bioremediation ...................................... 162 Strategies for use of biofilm in bioremediation ..................... 163

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Types of pollutants remediated by biofilms.......................... 164 Application of biofilm in bioremediation............................. 165 7.1 Persistent organic pollutants (POPs)........................... 165 7.2 Inorganic pollutants: heavy metals and synthetic dyes ... 166 7.3 Oil-contaminated water............................................ 167 7.4 Pharmaceutical and personal care products (PPCPs) ..... 168 7.5 Pesticides .............................................................. 168 Challenges in biofilm mediated bioremediation .................... 169 References ..................................................................... 170

CHAPTER 8 Microorganism: an ecofriendly tool for waste management and environmental safety ................. 175 Shubhangi Parmar, Sagar Daki, Sourish Bhattacharya and Anupama Shrivastav 1 2 3

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Introduction ................................................................... 175 Types of wastes and its sources ......................................... 176 Role of microorganisms in waste management ..................... 177 3.1 Sewage treatment.................................................... 178 3.2 Energy production................................................... 178 3.3 Treatment of soil .................................................... 178 3.4 Oil spills treatment.................................................. 179 Advantages of bioremediation over conventional methods...... 179 Different approaches for microbial waste management .......... 181 5.1 Bioleaching ........................................................... 182 5.2 Bioaugmentation..................................................... 182 5.3 Biostimulation........................................................ 183 5.4 Bioventing............................................................. 183 5.5 Biopiles ................................................................ 184 5.6 Biofiltration ........................................................... 184 5.7 Microbe assisted phytoremediation ............................ 185 Treatment of wastewater using microbes ............................. 186 6.1 Bacteria ................................................................ 186 6.2 Algae.................................................................... 186 6.3 Fungi.................................................................... 189 Challenges in microbial waste management by bioremediation................................................................ 189 Role of indigenous microorganisms for environmental protection ...................................................................... 190 Conclusion..................................................................... 191 References ..................................................................... 191

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CHAPTER 9 Microbial degradation of lignin: conversion, application, and challenges ................................. 195 Aryama Raychaudhuri and Manaswini Behera 1 2 3

Introduction ................................................................... 195 Chemical structure of lignin and sources ............................. 196 Biological degradation of lignin......................................... 198 3.1 Lignin degradation by fungi...................................... 199 3.2 Lignin degradation by bacteria .................................. 201 Enzymes associated with lignin degradation ........................ 203 4.1 Lignin peroxidase ................................................... 203 4.2 Manganese peroxidase............................................. 204 4.3 Versatile peroxidase ................................................ 205 4.4 Laccase................................................................. 205 4.5 Bacterial ligninolytic enzymes .................................. 206 Regulation of ligninolytic enzymes .................................... 207 5.1 Induction of metal ions ............................................ 207 5.2 Induction of ethanol ................................................ 208 5.3 Induction nutrients .................................................. 208 5.4 Induction of phenolic compounds .............................. 208 Bioconversion of lignin to value-added bioproducts .............. 209 6.1 Microbial lipids ...................................................... 209 6.2 Polyhydroxyalkanoates ............................................ 212 6.3 Vanillin ................................................................. 213 6.4 Muconic acid ......................................................... 214 Current challenges and future perspectives .......................... 214 Conclusion..................................................................... 215 References ..................................................................... 216

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CHAPTER 10 Ligninolytic enzymes: a promising tools for bioremediation of waste water............................ 221 Hiren K. Patel, Rishee K. Kalaria, Divyesh K. Vasava and Hiren N. Bhalani 1 2

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Introduction.................................................................. 221 Ligninolytic enzymes..................................................... 223 2.1 Molecular structure and mechanisms of ligninolytic enzymes...............................................................223 Laccases ...................................................................... 224 3.1 Laccase structure and catalytic mechanism.................224 Heme-peroxidases ......................................................... 225 Lignin peroxidase (LiP).................................................. 226

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CHAPTER 11

Manganese peroxidase (MnP).......................................... 227 Sources of ligninolytic enzymes....................................... 227 Application of ligninolytic enzymes ................................. 228 8.1 Delignification of lignocelluloses ............................229 8.2 Removal of recalcitrant polyaromatic hydrocarbons ...229 8.3 Conversion of coal to low molecular mass fraction ....230 8.4 Biopulping and biobleaching in paper industry..........230 8.5 Polymerization in polymer ventures ........................231 8.6 Biodegradation of colors .......................................231 8.7 Wastewater treatment............................................232 8.8 Soil treatment......................................................233 8.9 Lignolytic enzymes applications in various industries............................................................234 8.10 Role of ligninolytic enzymes in lignin degradation.....235 Improvement strategies for ligninolytic enzyme production .. 236 Conclusions.................................................................. 237 References ................................................................... 237

Bioaccumulation and detoxification of heavy metals: an insight into the mechanism................ 243 Mohita Chugh, Lakhan Kumar, Deepti Bhardwaj and Navneeta Bharadvaja

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Introduction.................................................................. 243 Industrial effluent containing heavy metals ........................ 244 2.1 Metal finishing ......................................................244 2.2 Mining.................................................................245 2.3 Textiles industries ..................................................245 2.4 Nuclear plants .......................................................245 Heavy metals in industrial effluent ................................... 245 3.1 Arsenic ................................................................245 3.2 Lead....................................................................246 3.3 Mercury ...............................................................246 3.4 Cadmium .............................................................246 Analysis of heavy metals................................................ 246 Heavy metal toxicity...................................................... 247 5.1 Environment .........................................................247 5.2 Plants ..................................................................248 5.3 Microorganisms.....................................................248 5.4 Humans................................................................249 Bioremediation ............................................................. 250 Bioaccumulation ........................................................... 252

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Detoxification............................................................... 253 Different types of bioremediators for heavy metals ............. 256 9.1 Algae...................................................................257 9.2 Fungi...................................................................258 9.3 Bacteria ...............................................................258 Integrated system .......................................................... 259 Conclusion and future perspectives................................... 260 References ................................................................... 261

CHAPTER 12 Membrane proteins mediated microbialelectrochemical remediation technology............. 265 Jesu´s Pe´rez-Garcı´a, Javier Bacame-Valenzuela, Diana Mayra Sa´nchez Lo´pez, Jose´ de Jesu´s Go´mez-Guzma´n, Martha Leticia Jime´nez Gonza´lez, Luis Ortiz-Frade and Yolanda Reyes-Vidal 1 2

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Introduction ................................................................. 265 Microbial electrochemistry ............................................. 267 2.1 Microbial-electrochemical systems for bioremediation ..................................................... 268 Membrane protein complex in electrogenic bacteria for bioremediation ............................................................. 270 3.1 Respiratory complexes of Shewanella oneidensis and heavy metals biodegradation................................... 270 3.2 Redox mediators of Pseudomonas aeruginosa in environmental bioremediation ................................. 272 3.3 Geobacter sulfurreducens cytochromes and nanowires in heavy metals reduction ........................ 272 Biological enzymes for environmental bioremediation......... 273 4.1 Oxidoreductases ................................................... 274 4.2 Peroxidases.......................................................... 274 4.3 Oxygenases.......................................................... 275 4.4 Monooxygenases .................................................. 275 4.5 Methane oxygenase (MMO) ................................... 276 4.6 Laccases.............................................................. 276 Electrochemical characterization of redox enzymes ............ 277 5.1 Cyclic voltammetry............................................... 277 5.2 Electrochemical impedance spectroscopy (EIS).......... 278 5.3 Coupled spectroscopic and electrochemical techniques ........................................................... 279 Perspectives ................................................................. 281 References ................................................................... 282

Contents

CHAPTER 13

Bioremediation strategies to overcome heavy metals and radionuclides from the environment....................................................... 287 Sanchayita Basu, Pujaita Banerjee, Sudeshna Banerjee, Bhaswati Ghosh, Arunima Bhattacharjee, Dipanjan Roy, Pragati Singh and Ashutosh Kumar

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Introduction ................................................................. 287 Microbial interactions with radionuclides and heavy metals . 289 Organisms involved in bioremediation.............................. 292 Bioremediation of heavy metals and radionuclides ............. 295 Limitations and future prospects...................................... 297 Conclusion .................................................................. 298 References ................................................................... 298

CHAPTER 14

Microbial remediation of tannery wastewater...... 303 Lakhan Kumar, Khushbu, Mohita Chugh and Navneeta Bharadvaja

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Introduction to tanneries ................................................ 303 Characteristics of tannery waste water.............................. 305 Environmental and health impacts ................................... 305 Wastewater treatment methods adopted in tanneries............ 308 4.1 Physicochemical remediation of tannery wastewater constituents.......................................................... 310 4.2 Biological treatment or bioremediation of tannery wastewater........................................................... 312 Microbial remediation ................................................... 312 5.1 Bacterial remediation of tannery effluent constituents.......................................................... 313 5.2 Phycoremediation or algal remediation of tannery wastewater constituents.......................................... 317 5.3 Fungal remediation or mycoremediation of tannery wastewater constituents.......................................... 317 Challenges and limitations to biological wastewater treatment methods employed in tannery industries.............. 320 Recent advancements .................................................... 321 7.1 Metagenomic approach for bioprospecting potential microbes and enzymes for tannery wastewater treatment............................................................. 321 7.2 Microbial biosensors for detection and monitoring of contaminants present in tannery wastewater............... 322 Solid waste management practices................................... 323 References ................................................................... 323

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CHAPTER 15 Biological methods for degradation of textile dyes from textile effluent .................................... 329 Muhammad Shoaib, Ambreen Ashar, Zeeshan Ahmad Bhutta, Iqra Muzammil, Moazam Ali and Ayesha Kanwal 1 2 3

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Introduction ................................................................. 329 Types and characteristics of dyes..................................... 332 Methods of dye removal ................................................ 333 3.1 Physicochemical methods....................................... 333 3.2 Biological methods ............................................... 334 Conclusion .................................................................. 350 References................................................................... 351

CHAPTER 16 Biodegradation of azo dye using microbiological consortium ........................................................ 355 Chitra Devi Venkatachalam, Mothil Sengottian, Sathish Raam Ravichandran and Sivakumar Venkatachalam 1 2

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Introduction ................................................................. 355 Azo dyes in textile industry ............................................ 356 2.1 Classification of azo dyes....................................... 356 2.2 Impact of textile effluents containing azo dyes on environment......................................................... 357 2.3 Different methods used in degradation of azo dyes ..... 359 Microbiological degradation of azo dyes........................... 359 3.1 Degradation mechanism with bacteria ...................... 360 3.2 Degradation mechanism with algae.......................... 362 3.3 Degradation mechanism with fungi.......................... 362 3.4 Advantages of using microbiological consortia .......... 363 Parameters involved during microbial azo-dye degradation .. 364 4.1 Effect of carbon source.......................................... 364 4.2 Effect of nitrogen source........................................ 364 4.3 Effect of dye concentration..................................... 366 4.4 Effect of inoculum size.......................................... 366 4.5 Effect of pH......................................................... 366 4.6 Effect of temperature............................................. 366 4.7 Effect of time....................................................... 367 4.8 Effect of agitation ................................................. 367 Conclusion .................................................................. 367 References................................................................... 368

Contents

CHAPTER 17

Removal of pesticides from water and waste water by microbes ............................................. 371 Pinal Bhatt and Anupama Shrivastav

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Introduction ................................................................. 371 Pesticide...................................................................... 372 2.1 Organochloride pesticide........................................ 374 2.2 Organophosphate pesticide ..................................... 375 2.3 Carbamate pesticide .............................................. 375 2.4 Other classes........................................................ 375 Impact of pesticide........................................................ 375 Metabolism and degradation of pesticide .......................... 378 4.1 Application of adsorbent ........................................ 378 Biodegradation ............................................................. 382 5.1 Types of pesticides-degrading microorganism ............ 384 5.2 The mechanism of microbial degradation of pesticides ............................................................ 384 5.3 Commonly used pesticide degradation of microorganisms .................................................... 388 5.4 Microbial degradation of pesticide technology ........... 388 Factors affect biodegradation .......................................... 389 6.1 Environmental factors............................................ 390 6.2 Effect of pesticide structure .................................... 391 6.3 The impact of microorganisms ................................ 392 Current scenario ........................................................... 392 Conclusion .................................................................. 394 References................................................................... 395

An ecofriendly approach toward waste management and environmental safety through microorganisms ................................................. 401 Kunwali Das, Suraj Chetri, Priya Khadgawat, Sidak Minocha, Aveepsa Sengupta, Bipin Kumar Sharma and Ashutosh Kumar

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Introduction ................................................................. 401 Microorganisms in the environment ................................. 403 2.1 Bacteria .............................................................. 403 2.2 Fungi.................................................................. 404 2.3 Viruses................................................................ 404 2.4 Protozoa.............................................................. 405 2.5 Algae.................................................................. 405 2.6 Archaea .............................................................. 406

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Microorganisms for waste management ............................ 406 3.1 Industrial waste .................................................... 406 3.2 Municipal waste ................................................... 408 3.3 Agricultural wastes ............................................... 409 3.4 Biomedical waste.................................................. 409 3.5 Radioactive waste ................................................. 410 Microorganisms in environmental safety........................... 410 Conclusion .................................................................. 413 References................................................................... 414

CHAPTER 19 Enzymatic decolorization and degradation of azo dyes ............................................................ 419 Devikaben Bharatbhai Vishani and Anupama Shrivastav 1 2 3 4

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Introduction................................................................. 419 Dyes........................................................................... 420 Azo dye ...................................................................... 420 Classification of azo dyes............................................... 421 4.1 Acid dyes ............................................................ 421 4.2 Basic or cationic dyes............................................ 421 4.3 Direct dyes .......................................................... 421 4.4 Mordant dyes ....................................................... 421 4.5 Vat dyes .............................................................. 422 4.6 Azoic dyes........................................................... 422 4.7 Reactive dyes....................................................... 422 4.8 Disperse dyes....................................................... 422 4.9 Solvent dyes ........................................................ 423 Strucutre of dyes .......................................................... 423 Different method for the removal of dyes ......................... 423 6.1 Degradation methods of dyes.................................. 424 6.2 Biologycal method................................................ 426 Decolorization and degradation of azo dyes by azoreductase ................................................................ 428 7.1 Decolorization and degradation azo dyes by laccase ... 428 Factor affecting dyes degradation by biological method ...... 429 8.1 pH...................................................................... 429 8.2 Temperature......................................................... 429 8.3 Oxygen ............................................................... 430 Mechanism of azo dyes ................................................. 430 Conclusion .................................................................. 430 Further reading............................................................. 431

Contents

CHAPTER 20

Azo dyes: a notorious class of water pollutant, and role of enzymes to decolorize and degrade them..................................................... 433 Vivek Chauhan, Priya Gautam and Shamsher S. Kanwar

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CHAPTER 21

Introduction ................................................................. 433 Enzyme-meditated decolorization and degradation of azo dye ....................................................................... 434 Mechanism of degradation and decolorization by peroxidases.................................................................. 436 3.1 Manganese peroxidase........................................... 437 3.2 Lignin peroxidase ................................................. 438 3.3 Horseradish peroxidase .......................................... 438 Mechanism of degradation and decolorization by laccase .... 439 Mechanism of degradation and decolorization by azoreductases ............................................................... 441 Conclusion .................................................................. 444 Acknowledgments......................................................... 445 References................................................................... 445

Biofilm mediated bioremediation and other applications....................................................... 449 Rajalakshmi Sridharan and Veena Gayathri Krishnaswamy

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Introduction.................................................................. 449 Biofilms in bioremediation.............................................. 450 Bioreactors in biofilm formation ...................................... 451 Biofilm mediated remediation.......................................... 452 Marine biofilms............................................................. 453 Marine biofilm in elimination of plastic debris ................... 454 Factors affecting the remediation using biofilm................... 455 7.1 Nature of matrix ....................................................455 7.2 pH.......................................................................455 7.3 Temperature..........................................................456 Qs in pollutant degradation ............................................. 456 Biofilms as source for value added products....................... 456 Conclusion................................................................... 456 References................................................................... 457

Index...................................................................................................461

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Contributors Kunwali Das Department of Microbiology, Tripura University (A Central University), Agartala, Tripura, India Moazam Ali Department of Clinical Medicine and Surgery, University of Agriculture, Faisalabad, Punjab, Pakistan Jayshree Annamalai Centre for Environmental Studies, Department of Civil Engineering, Anna University, CEG Campus, Chennai, Tamil Nadu, India Ambreen Ashar Department of Chemistry, Government College Women University, Faisalabad, Punjab, Pakistan Javier Bacame-Valenzuela Center of Research and Technological Development in Electrochemistry, Quere´taro Technology Park, Pedro Escobedo, Quere´taro, Me´xico; CONACYTCenter of Research and Technological Development in Electrochemistry, Quere´taro Technology Park, Pedro Escobedo, Quere´taro, Me´xico Pujaita Banerjee Department of Life Sciences, Presidency University, Kolkata, West Bengal, India Sudeshna Banerjee Department of Microbiology, Amity University, Lucknow, Uttar Pradesh, India Sanchayita Basu Department of Microbiology, Tripura University (A Central University), Agartala, Tripura, India Manaswini Behera School of Infrastructure, Indian Institute of Technology Bhubaneswar, Bhubaneswar, Odisha, India Hiren N. Bhalani College of Agriculture, Junagadh Agricultural University, Junagadh, Gujarat, India Navneeta Bharadvaja Plant Biotechnology Laboratory, Department of Biotechnology, Delhi Technological University, New Delhi, Delhi, India Devikaben Bharatbhai Vishani Department of Microbiology, Parul Institute of Applied Sciences, Parul University, Vadodara, Gujarat, India

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Deepti Bhardwaj Plant Biotechnology Laboratory, Department of Biotechnology, Delhi Technological University, New Delhi, Delhi, India Pinal Bhatt Department of Microbiology, Parul Institute of Applied Sciences, Parul University, Vadodara, Gujarat, India Joyani Bhattacharjee Department of Biotechnology, Haldia Institute of Technology, Haldia, West Bengal, India Arunima Bhattacharjee Department of Microbiology, Tripura University (A Central University), Agartala, Tripura, India Sourish Bhattacharya Process Design and Engineering Cell, CSIR Central Salt and Marine Chemicals Research Institute, Bhavnagar, Gujarat, India Zeeshan Ahmad Bhutta The Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush Campus, Midlothian, Scotland, United Kingdom Pitam Chakrabarti Department of Biotechnology, Haldia Institute of Technology, Haldia, West Bengal, India Vivek Chauhan Department of Biotechnology, Himachal Pradesh University, Summer Hill, Himachal Pradesh, India Suraj Chetri Department of Zoology, Cotton University, Guwahati, Assam, India Mohita Chugh Plant Biotechnology Laboratory, Department of Biotechnology, Delhi Technological University, New Delhi, Delhi, India Anjali Dahiya Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati, Assam, India Sagar Daki Process Design and Engineering Cell, CSIR Central Salt and Marine Chemicals Research Institute, Bhavnagar, Gujarat, India Jose´ de Jesu´s Go´mez-Guzma´n Center of Research and Technological Development in Electrochemistry, Quere´taro Technology Park, Pedro Escobedo, Quere´taro, Me´xico

Contributors

Subhasish Dutta Department of Biotechnology, Haldia Institute of Technology, Haldia, West Bengal, India Salman Farissi Department of Environmental Science, School of Earth Science Systems, Central University of Kerala, Kasaragod, Kerala, India Janhavi Gadkari Department of Microbiology, Parul Institute of Applied Sciences, Parul University, Vadodara, Gujarat, India Priya Gautam Department of Biotechnology, Himachal Pradesh University, Summer Hill, Himachal Pradesh, India Bhaswati Ghosh Department of Microbiology, Sarsuna College, University of Calcutta, Kolkata, West Bengal, India Martha Leticia Jime´nez Gonza´lez Center of Research and Technological Development in Electrochemistry, Quere´taro Technology Park, Pedro Escobedo, Quere´taro, Me´xico Rishee K. Kalaria ASPEE Shakilam Biotechnology Institute, Navsari Agricultural University, Surat, Gujarat, India Ayesha Kanwal Institute of Biochemistry, Biotechnology and Bioinformatics, The Islamia University of Bahawalpur, Bahawalpur, Punjab, Pakistan Shamsher S. Kanwar Department of Biotechnology, Himachal Pradesh University, Summer Hill, Himachal Pradesh, India Priya Khadgawat Department of Genetics, University of Delhi, New Delhi, Delhi, India Khushbu Department of Applied Chemistry, Delhi Technological University, New Delhi, Delhi, India Veena Gayathri Krishnaswamy Department of Biotechnology Stella Maris College (Autonomous), Affiliated to University of Madras, Chennai, Tamil Nadu, India Deepak Kumar Amity Institute of Biotechnology, Amity University Haryana, Gurugram, Haryana, India

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Lakhan Kumar Plant Biotechnology Laboratory, Department of Biotechnology, Delhi Technological University, New Delhi, Delhi, India Ashutosh Kumar Department of Microbiology, Tripura University (A Central University), Agartala, Tripura, India Sangeeta Kumari Amity Institute of Biotechnology, Amity University Haryana, Gurugram, Haryana, India Sidak Minocha Department of Genetics, University of Delhi, New Delhi, Delhi, India Muthukumar Muthuchamy Department of Environmental Science, School of Earth Science Systems, Central University of Kerala, Kasaragod, Kerala, India Anbazhagi Muthukumar Department of Environmental Science, School of Earth Science Systems, Central University of Kerala, Kasaragod, Kerala, India Iqra Muzammil Department of Clinical Medicine and Surgery, University of Agriculture, Faisalabad, Punjab, Pakistan Luis Ortiz-Frade Center of Research and Technological Development in Electrochemistry, Quere´taro Technology Park, Pedro Escobedo, Quere´taro, Me´xico Ashok Pandey CSIR-Indian Institute of Toxicological Research, Lucknow, Uttar Praesh, India Shubhangi Parmar Process Design and Engineering Cell, CSIR Central Salt and Marine Chemicals Research Institute, Bhavnagar, Gujarat, India Hiren K. Patel School of Sciences, P P Savani University, Surat, Gujarat, India Bhisma K. Patel Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati, Assam, India S.M. Paul Khurana Amity Institute of Biotechnology, Amity University Haryana, Gurugram, Haryana, India

Contributors

Jesu´s Pe´rez-Garcı´a Center of Research and Technological Development in Electrochemistry, Quere´taro Technology Park, Pedro Escobedo, Quere´taro, Me´xico Sneha Ramesh Department of Environmental Science, School of Earth Science Systems, Central University of Kerala, Kasaragod, Kerala, India Sathish Raam Ravichandran Department of Chemical Engineering, Kongu Engineering College, Erode, Tamil Nadu, India Aryama Raychaudhuri School of Infrastructure, Indian Institute of Technology Bhubaneswar, Bhubaneswar, Odisha, India Yolanda Reyes-Vidal Center of Research and Technological Development in Electrochemistry, Quere´taro Technology Park, Pedro Escobedo, Quere´taro, Me´xico; CONACYTCenter of Research and Technological Development in Electrochemistry, Quere´taro Technology Park, Pedro Escobedo, Quere´taro, Me´xico Dipanjan Roy Department of Agricultural Biotechnology, Ramkrishna Mission Vivekananda Educational and Research Institute (RKMVERI), Kolkata, West Bengal, India Ashish Kumar Sahoo Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati, Assam, India Mothil Sengottian Department of Chemical Engineering, Kongu Engineering College, Erode, Tamil Nadu, India Aveepsa Sengupta Department of Microbiology, Tripura University (A Central University), Agartala, Tripura, India Bipin Kumar Sharma Department of Microbiology, Tripura University (A Central University), Agartala, Tripura, India Muhammad Shoaib Institute of Microbiology, University of Agriculture, Faisalabad, Punjab, Pakistan; Key Laboratory of New Animal Drug Project, Gansu Province, Key Laboratory of Veterinary Pharmaceutical Development, Ministry of Agriculture, Lanzhou Institute of Husbandry and Pharmaceutical Sciences of CAAS, Lanzhou, China

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Contributors

Anupama Shrivastav Department of Microbiology, Parul Institute of Applied Sciences, Parul University, Vadodara, Gujarat, India Pragati Singh Department of Microbiology, Tripura University (A Central University), Agartala, Tripura, India Rajalakshmi Sridharan Department of Biotechnology Stella Maris College (Autonomous), Affiliated to University of Madras, Chennai, Tamil Nadu, India Diana Mayra Sa´nchez Lo´pez Center of Research and Technological Development in Electrochemistry, Quere´taro Technology Park, Pedro Escobedo, Quere´taro, Me´xico Sabeela Beevi Ummalyma Institute of Bioresources and Sustainable Development (IBSD), An Autonomous Institute Under Department of Biotechnology, Government of India, Takyelpat, Imphal, Manipur, India Divyesh K. Vasava College of Agriculture, Junagadh Agricultural University, Junagadh, Gujarat, India Chitra Devi Venkatachalam Department of Food Technology, Kongu Engineering College, Erode, Tamil Nadu, India Sivakumar Venkatachalam Department of Chemical Engineering, AC Tech Campus, Anna University, Chennai, Tamil Nadu, India

CHAPTER

A comparative study between physicochemical and biological methods for effective removal of textile dye from wastewater

1

Subhasish Dutta, Joyani Bhattacharjee Department of Biotechnology, Haldia Institute of Technology, Haldia, West Bengal, India

1. Introduction One of the major sources of pollution in nature is industrial wastewater. Due to high global development, various chemical agents like dyes, pigments, and other aromatic compounds are used in industries such as textile, printing, pharmaceuticals, and plastics to generate products with better results (Khan and et al., 2020). Various studies have confirmed that an average sized textile industry consumes around 1.6 million liters of water per day for the production of about 8000 kg of fabric. A research from World Bank has said around 17%e20% of textile industry water pollution comes from dyeing and finishing treatments that are applied to the fabric. The processes included in the main steps of textile industry are resizing, dyeing, printing and some finishing steps. The finishing steps are softening, cross-linking and waterproofing and they require a huge amount of water supply (Nemr, 2012; Bhatia et al., 2017). Large amount of effluents are generated from dyeing and the finishing processes. Dyeing can be defined as the process of applying colors to the fabrics which are resistant to the effect of light, water, and soap. Tannin and lignin are considered examples of coloring agents. For various other processes to be carried out in the textile industry, a particular mixture is made out of chemicals, dye stuffs, and water. Once the process is completely done this mixture is released into various water bodies (Anjaneyulu et al., 2005). The presence of suspended solid particles, high chemical oxygen demand (COD), synthetic dyes, and heavy metals such as lead, mercury, and cadmium have been considered to increase the toxicity of water. These textile effluents alter the color and composition of the water bodies making it very hazardous for the marine ecosystem (Nguyen and Ruey-Shin, 2013). Dyes have high thermal and photo stability which helps them to persist for an extended period of time in the water environment if left untreated. The dark color imparted by these toxic chemicals reduces the sunlight penetration thus hampering photosynthesis. They also inhibit the growth and activity of microorganisms. Development in Wastewater Treatment Research and Processes. https://doi.org/10.1016/B978-0-323-85657-7.00003-1 Copyright © 2022 Elsevier Inc. All rights reserved.

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The effluents generated from these textile industries are not only considered to be toxic for the aquatic ecosystem but they are also enriched by the presence of various carcinogenic and mutagenic substances which are harmful to human beings too. For instance, the very famous azo dye, which is one of the main components of textile industry, is very much responsible for bladder cancer in humans (Ramachandran et al., 2013). They also cause severe damage to kidney, brain, reproductive system. Therefore, in this chapter an effort has been made in discussing the preexisting physiochemical methods to remove toxicity from textile effluents and their inefficiencies and cost effectiveness, with special focus on biological methods which have been found beneficial.

2. Types of dyes and their toxicity One of the most important sources of water pollution globally is the toxic effluents generated from textile industry (Porter, 1973). The main contaminants are generally produced from dyes and finishing processes (El Harfi and El Harif, 2017). Dyes can be defined as complex, unsaturated organic compounds which are soluble in either oil or water. When dyes are applied to substances, it imparts colors through a process which changes the crystalline structure of colored substance (Porter, 1973; Benkhaya et al., 2020). Solubility of different dyes in water also differs from one another. Dyes are widely used in various industries such as textile, pharmaceuticals, plastics, cosmetics, and so forth. During the middle of 19th century natural dyes were synthesized for the first time. They were synthesized mostly from natural substances like animals, plants, insects and minerals. These dyes are generally nonsubstantive and are usually applied on textiles with the help of mordents which have affinity for both the fiber and the coloring substance. In comparison to synthetic dyes, these natural dyes are much less toxic and are also easily treated by biodegradation. In 1871, the first synthetic dye was produced by Woulfe who treated indigo, a natural dye with nitric acid to produce picric acid (El Harfi and El Harif, 2017). Nearly 10,000 different kinds of textile dyes and pigments are used. 7
105 tons of synthetic dyes are produced globally, annually (Singh and Arora, 2011; Ramachandran et al., 2013). Dyes can be classified into two categories, based on presence of chromophoric groups in their chemical structures and usage or application methods (Nemr, 2012). A chromophore is an atom or a group of atom who is responsible for production of color because of its ability to absorb light in a near UV region. Compounds bearing the chromophores are called chromogen. Examples of some chromophoric groups are N¼O, -NO2, -N¼N-, -C¼O, (CH-CH)n, C¼S, and -C¼N (Benkhaya et al., 2020). Auxochromes can be defined as a group which does not itself act as a chromophore, but whose presence alters the intensity as well as wavelength of absorption. These groups can be acidic or basic in nature. Examples of some acidic groups are -OH, -COOH, -SO3H. Examples of some basic groups are -NH2, -NHR, and -NR2 (Benkhaya et al., 2020; Singh and Arora, 2011).

2. Types of dyes and their toxicity

Based on the presence of chromophoric groups, dyes can be classified into more than 20e30 groups. Out of which most important ones are nitro dyes, nitroso dyes, azo dyes, trimethyl ethane dyes, phthalein dyes, indigo dyes, anthraquinone dyes, and sulfur dye (Benkhaya et al., 2020; Ramachandran et al., 2013).

2.1 Azo dyes Of all kinds of synthetic dyes, azo dye derivatives are the most widely used ones around 70% in the textile industries (Nemr, 2012). It has been found out that nearly 1million azo dyes are produced annually. They have -N¼N-chromophoric group in their structure. Azo dye can again be classified into disazo, trisazo, monazo, polyazo, and tetrakisazo based on the number of azo dye linkage present (Benkhaya et al., 2020). The immense popularity of azo dyes is due to some factors. They are the variations and adaptations that are needed for the multipurpose use of these dyes and the high molar extinction of azo dye compounds (El Harfi and El Harif, 2017). Azo dyes are formed in situ when two colorless or slightly colored compounds called napthols react (Benkhaya et al., 2020). These azo dyes when conjugated with heterocyclic aromatic groups, complex structures are formed. These structures help in the expression of various colors in the dye. One of the major drawbacks of using azo dye in the textile industry is, azo dye on reaction with any blue-violet range of colors gives a dull shade (Benkhaya et al., 2020). A total of 896 dyes whose chemical structures are known and they are available in the textile database. According to the European Annex XVII of reach, there are 22 regulated aromatic amines and only 426 out of 898 dyes can generate a variety or two of them (Benkhaya et al., 2020). Azo amino dyes can be considered as a suitable example for organic compounds consisting of zwitterionic resonance system (Singh and Ram, 2017). Nowadays synthetic dyes are preferably more used than natural ones. Azo dyes, despite having such a huge impact in the textile industry, have a lot of major harmful effects too (Saini, 2017). It was noticed that the nitro group present in the azo dyes, after breaking down generates obnoxious products such as 1, 4-phenylenediamine, and o-tolidine, which were proved to be mutagenic in nature. 3-methoxy-4-aminoazobenzene, an aromatic amine was found to be hepatocarcinogen in rats and a source of potent mutagen in bacteria (Saini, 2017; Singh and Ram, 2017). There are few specific cases where the azo dyes after being biodegraded by microorganisms are producing certain derivatives that are found to be highly toxic. For example, there is a commercial textile dye, namely Acid Violet 7, which is toxic enough to cause lipid peroxidation, chromosomal aberrations and inhibition of enzyme acetylcholinesterase. This dye when biodegraded using Pseudomonas putida, breaks down into respective metabolites such as 4-aminoacetanilide and 5-acetamido-2-amino-1-hydroxy-3, and 6-naphtalene disulfonic acid, which is far more toxic than Acid Violet 7 (Nemr, 2012). Based on application method, textile dyes can be classified into the following.

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2.2 Acid dye Due to interactions between the protons of the fiber and the negative charge of the dyes due to the presence of sulfonic or carboxylic acid groups, acid dyes are considered to be highly water soluble anionic dyes. These dyes, compared to direct dyes and vat dyes, and have poor lightfastness on textile dyes. According to chemical composition, acid dyes can be classified into azo, anthraquinone, triarylmethane, nitro, and nitroso compounds (Porter, 1973).

2.3 Basic dye These are water soluble cationic dyes which give high intensity and bright colors that are visible even at low concentration. These dyes bind with fibers like wool, polyester which have exclusive anionic sites to bind with the cationic parts of these basic dyes. Major chemical categories are diazahemicyanine, triarylmethane, cyanine, hemicyanine, thiazine, oxazine, and acridine (Porter, 1973).

2.4 Direct dye These are anionic dyes that are water soluble in nature. They contain sulfonic acid group, which have affinity toward cellulose fibers mainly azo compounds that come under this group. Main advantage of direct dye over fiber-reactive dyes is that direct dyes are more resistive in fading out under light (Porter, 1973).

2.5 Vat dye These are the type of dyes which require oxygen to develop their color. These dyes are usually insoluble in water but are soluble in alkali reduction, i.e., sodium dithionite in the presence of sodium hydroxide common compounds are anthraquinone or indigoids (Nemr, 2012). These synthetic dyes are highly toxic in nature. So when these dye effluents from the industries are discharged into the water bodies, it not only increases pollution but also is very much harmful to all the living beings. Thus, we discuss few physico-chemical methods and the adversities associated with those processes and the need to choose certain biological methods to eradicate the problem of textile dye toxicity (Singh and Arora, 2011; Ramachandran et al., 2013). The untreated effluents from the textile industries when dumped in water bodies cause serious side effects on animals and plants (Natarajan et al., 2018). Thus various conventional approaches have been taken into consideration to treat the effluents (Anjaneyulu et al., 2005) (Table 1.1).

3. Physical methods Physical methods can be defined as a straight forward method to remove toxic effluents from wastewater by the application of forces such as gravitation, electrical

3. Physical methods

Table 1.1 Classification of dyes. Class of dye

Chromophoric group

Example

Azo dye

Methyl orange

Nitro dye

Acid yellow 24

Indigo dye

Acid blue71

Anthraquinone dye

Reactive blue 4

Pthalein dye

Phenolphthalein

Triphenyl Methane dye

Malachite green

Nitroso dye

Fast green O

Sulfur dye

Indophenol

Xanthene dye

Rhodamine B

Modified from El Harfi, S., El Harfi, A., 2017. Classifications, properties and applications of textile dyes: a review. Appl. J. Environ. Eng. Sci. 3 (3), 00000e00003 and Singh, P.K., Ram, L.S., 2017. Bio-removal of azo dyes: a review. Int. J. Appl. Sci. Biotechnol. 5 (2), 108e126.

attraction, and van der Waal’s force. Of all the three methodologies (physical, chemical, and biological), physical method is the most used one as it is much simpler, efficient, and the least amount of chemicals and biological organisms are used (Vanitha et al., 2018).

3.1 Adsorption Of all the available physical methods, adsorption has been proven to be the most efficient and widely used technology to treat waste water effluents (Anjaneyulu et al., 2005). Adsorption can be defined as a physicochemical mass transfer process where

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CHAPTER 1 A comparative study between physicochemical and biological

elements are concentrated on the surface of the adsorbent (solid or liquid). This process happens in the interface of either two similar or different states for example, liquid-liquid, gas-liquid, and solid-liquid (Natarajan et al., 2018). The process of adsorption has been considered as one of the most feasible equilibrium separation techniques to remove toxic effluents from water bodies due to its economic efficiency and also due to the production of high quality products (Natarajan et al., 2018). To perform adsorption, no pretreatment is required. Often, it is used as a posttreatment for various other conventional methods as the process doesn’t produce additional toxic matters as a result in the end (Vanitha et al., 2018). The surface on which the process of adsorption takes place is called adsorbent and the adsorbates are the molecules that get adhered to the surface of adsorbent. If the process of adsorption is characterized by low heat generation and is reversible in nature, it is called physisorption (physical adsorption). If the process is characterized by high heat generation and is irreversible in nature with chemical force acting between adsorbate and adsorbent, it is called chemisorptions (chemical adsorption) (Natarajan et al., 2018). Factors affecting adsorption: There are certain physicochemical factors associated with adsorption such as temperature, pH, solution concentration, nature of adsorbate (molecular structure, size, and weight), surface charge, and time duration of contact (Vanitha et al., 2018; Saini, 2017). Due to the rising popularity of the adsorption process, a vast range of adsorbents are used nowadays. Few of them are chitin, almond peels, fly ashes, baggase, activated carbon, sugarcane, etc.

3.1.1 Adsorption by clay particles Clays are low cost raw materials used for making zeolites. Zeolites are used widely in adsorption, ion exchange and irradiation process. Kaolinite and montmorillonite are two types of clay minerals, they are widely used as dye adsorbents. Cationic dye, methylene blue is absorbed by kaolinite at a rate of 16 mg/g min. Whereas, for montmorillonite the rate varies from 10 mg/g min in the first 5minto 0.55 mg/g min over the next hour to 0.07 mg/g min for the final hour. Such difference in adsorption rate is due to the variance in anionic exchange rate of the clays (Nguyen and Ruey-Shin, 2013).

3.1.2 Adsorption by activated carbon This is one of the most common techniques of removal of effluents. Efficiency of activated carbon depends on the nature of carbon particle used and also the kind of dye effluent it is applied on. For instance, activated carbon is most useful in adsorbing cationic, mordant and acid dyes (90%). Efficiency of activated carbon reduces for removal of sulfur, dispersed, and reactive dyes (40%). But this issue can be solved by using an excess amount of activated carbon (Saini, 2017; Robinson et al., 2001). Activated carbon particles can be made from anything carbonaceous. Scientists long used coal as a source, but because coal is a nonrenewable source of energy, activated carbon is now synthesized from renewable, cost-efficient

3. Physical methods

substances like biomass, waste materials, and so forth (Vanitha et al., 2018). Activated carbon particle comes in different shapes and sizes. Powdered activated carbon (PAC) is very fine in structure thus they can stay suspended for longer while and making it difficult to be reused. Adding a little quantity of polyaluminum chloride can enhance the decolorization rate making it easier to collect the sludge from settling tank and reuse them. In case of granular activated carbon (GAC), it is easier to replace the GAC packed bed with fresh amount of carbon particles when exhausted (Nguyen and Ruey-Shin, 2013).

3.1.3 Adsorption by wood chips These are best used for the adsorption of acid dyes. But they are not widely used as these wood chips are usually nonrenewable and are burned down to generate power after being used as adsorbents (Robinson et al., 2001).

3.1.4 Adsorption by silica gel It is an effective way of removing basic dyes but it is not used much commercially due to the huge amount of side reactions associated with it (Robinson et al., 2001).

3.2 Coagulation and flocculation Coagulation is one of the conventional methods of treating wastewater toxicity. This method is mostly effective for disperse dyes (Anjaneyulu et al., 2005). To reduce the number of colored effluents from the water bodies, positively charged coagulants are formed from hydrolysis of metal salts such as iron, aluminum etc. (Anjaneyulu et al., 2005). These coagulants join together with the negative dye particles forming neutral clusters which then become macro enough to get filtered. The coagulating agents are generally polymers which are synthetic in nature having a high molecular rate and linear structure. Generally used coagulants are aluminum sulfate, aluminum chloride, ferric chloride, ferric sulfate, cationic organic polymers, etc. (Anjaneyulu et al., 2005). During the preparation of the macroflocs, the flocculants are added slowly. There are certain factors that alter the process of coagulation. There are chemicals present, pH, temperature, mixing time, and retention speed of the system, which affects the process of coagulation (Verma et al., 2012). Electro coagulation is the electro chemical treatment of textile dyes, where electrolytic reactions are performed followed by the process of coagulation and sedimentation. This treatment has been proven to be extremely effective even at higher pH. This method has been most effective for direct dye removal from wastewater (Verma et al., 2012). From the research conducted by Yang et al. it was concluded that Al-coagulation is much more effective for the removal of direct, disperse and reactive dyes. During the process, OH is formed in the cathode which in turn increases the solution pH, thus restoring the solution color and dissolving the coagulants. Whereas Fe-coagulation method is used for color removal from effluents while forming NaCIO, a strong oxidizing agent as a byproduct which helps in further decomposition of the dye structure (Yang and McGarrahan, 2005).

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CHAPTER 1 A comparative study between physicochemical and biological

3.2.1 Irradiation This is the simplest yet effective technique to remove textile dye effluents from waste water. This process requires a large amount of UV radiation and constant dissolved oxygen supply. Titanium dioxide acts as a catalyst in the process. On treating a secondary effluent with irradiation of gamma ray it was found that there was a reduction of 64% COD, 34% TOC, and 88% of color (Anjaneyulu et al., 2005; Robinson et al., 2001).

3.3 Emerging physical method for the treatment of textile dye effluents 3.3.1 Biosorption Various physical methods have been chosen for the removal of textile dye effluents from waste water. But most of these methods are cost effective and are meant for low scale in situ treatment. Biosorption can be defined as the process of accumulating toxic effluents with the help of microorganisms. Depending on the kind of textile dye, the rate of binding of the microorganism differs too (Robinson et al., 2001). On the experiment conducted by Sulak et al. to study the biosorption of aqueous textile effluents by wheat bran, it was inferred that wheat bran was effective in removing effluents of certain textile dyes such as are Reactive Red 180, Reactive black5, Reactiveorange16, Directred80, Acid red, Acid yellow 199 from the aqueous solution. The percentage of dye removal was found to be directly proportional to the amount of biosorbent and textile dyes present in the solution. Thermodynamically, the process was noted to be spontaneous and exothermic. On plotting the biosorption data in the Langmuir isotherm, adsorption was found to be monolayer (Sulak and Cengiz Yatmaz, 2012).

4. Membrane technology Membrane technology can be considered as one of the most effective and costefficient methods which not only help in decolorization but also in reduction of BOD and COD of wastewater. The main advantage of membrane technology is that the drench can be further reused. This kind of technology is immensely useful in places where there is shortage of water (Buckley, 1992). On the basis of classification of dye and degree of separation of effluents, this process can be classified into four types.

4.1 Microfiltration This is one of the oldest yet most capable ways of removing suspended particles having aperture approximately 0.1e1 mm. Through this process of microfiltration wide range of contaminants such as suspended particles, yeast cells, large pathogens, and so forth can be separated. Microfiltration is usually performed prior to reverse osmosis and nanofiltration (Buckley, 1992; Anis et al., 2019).

5. Chemical methods

4.2 Reverse osmosis This method is effective in both wastewater and desalination treatments. It can also remove various organic contaminants and harmful pathogens. RO is considered to be a pressure driven process where a semipermeable membrane reject particles based on size, charge, and interaction between the solute and solvent. RO membranes have nearly 90% retention rate when it comes to ionic compounds. The osmotic pressure involved in the process is directly proportional to the amount of salts dissolved therefore to the energy required (Xu and Lebrun, 1999; Malaeb and Ayoub, 2011).

4.3 Nanofiltration The process of nanofiltration also known as charged filtration is performed after adsorption to minimize the polarization concentration happening during the filtration process. It has the advantage of both reverse osmosis and ultrafiltration (UF), i.e., application of moderate pressure like UF and separations of solutions like reverse osmosis. Commercially available nanofiltration membrane have been used to treat cotton textile dye effluents (Buckley, 1992; Xu and Lebrun, 1999).

4.4 Ultrafiltration UF can be considered as a one-step removal of secondary effluents. UF can be considered as an RO pretreatment. In many cases UF membranes have been found using hollow fiber geometry (Xu and Lebrun, 1999). From the experiment conducted by Paz’dzior et al. for the removal of azo dye by the amalgamation of nanofiltration with biological methods, it was concluded that almost 90% color removal was evident and pure colorless filtrate was obtained having adequate quantity of salt and alkali concentration. Due to the formation of cleavage of Reactive Red 120, orthanilic acid was released. In an aerobic reactor, this acid was further degraded whereas in the sequencing batch reactor, the aromatic amine was not degenerated using the microbial culture (Pa
zdzior et al., 2009). _ Zy11a et al. performed an experiment with real wastewater collected from two textile plants. On applying nanofiltration on these textile effluents it was found that there was significant deterioration in the COD and textile colors. The further concentrated product in the nanofiltration was made to undergo anoxic biological treatment. It was observed that there was approximately 50% reduction in the COD. It was also inferred that the filtrate received from nanofiltration could be _ used as process water for the rest of the process (Zy11a et al., 2006).

5. Chemical methods Chemical methods of dye removal can be defined as a collection of certain conventional methods performed by utilizing chemical theories to remove textile dye

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effluents. This method requires specific set of equipments and high electrical energy to work efficiently. Usually chemical technologies have been proven to have success rate of 88%e99% (Vanitha et al., 2018).

5.1 Fenton method H2O2eFe (II) is known as Fenton’s reagent. It is very useful for the removal of toxic effluents from wastewater which normally resists the biological or physical degradation due to their toxicity to living biomass. CI Reactive Yellow 15 has high COD and resists degradation. But on reaction with Fenton’s reagent it was found to have decolorization of 98% and approximately 93% removal of COD. Fenton’s reagent in association with oxidation process was reported to be effective in degradation of approximately 20 different classes of dyes namely acid, reactive, direct, cationic, disperse, and vat in their aqueous solutions. Whereas color removal was found to be around 80%e100% for acid, reactive, cationic dyes and for water insoluble dyes like vat and disperse dye it was found to be as low as 30%e60%. Electro-Fenton process can be defined as an indirect electrochemical treatment used to degenerate and decolorize toxic textile effluents in this process, hydroxyl radical which is formed by Fenton’s reagent is produced electrochemically in situ. Hydroxyl radical, being excellent oxidizing agent can oxidize organic effluents until complete mineralization (Robinson et al., 2001; Lahkimi et al., 2007; Singh and Arora, 2011). Panizza et al. in his experiment studied the electrochemical treatment of real wastewater containing naphthalene and anthroquinone-sulfonic acid. The procedure was tried by the electro coagulation of Fenton’s reagent using graphite cathodes. To find out the optimum operating conditions, he also analyzed, the effect of cathode potential, Fe2þ concentration and cathode surface pretreatment (Panizza and Cerisola, 2001).

5.2 Ozonation This is one of the most effective chemical processes for nearly complete removal of textile dye effluents from waste water. Ozone is an excellent oxidizing agent compared to chlorine, hydrogen peroxide, and other oxidizing agents due to its high instability. The proportion of ozone to be used in the process is directly proportional to the amount of color and residual COD to be removed. The end product of ozonation can be easily discharged in the water bodies easily due to the lesser amount of color and COD present. Ozone can be applied in gaseous state thus volume of the sludge is not increased (Vanitha et al., 2018). In an experiment conducted by Lin et al., three strengths of waste water effluent were collected low, medium and high. The COD and color content of the effluents were observed to intensify from low to high in the three containers. For low strength, it was inferred that only ozonation was sufficient for decolorization and to remove turbidity. But for medium and high strength, ozonation was found to be effective for the removal of color but not

5. Chemical methods

for turbidity reduction. Thus, coagulation with aluminum sulfate or PAC was necessary. Even with the amalgamation of chemical coagulation with ozonation, approximately 70% COD could be reduced (Lin and Lin., 1993).

5.3 Cucurbitiril These are cyclic oligomer molecules made up of glycoluril and formaldehyde. Glycoluril is formed from glyoxal and urea. The monomers are held together by methylene bridges. The origin of the name cucurbitiril is from the Latin word Cucurbita maxima which is the scientific name for pumpkin, for its pumpkin like structure. The uril part of cucurbitiril emphasizes on the presence of urea. It was inferred that cucurbitiril has extremely good sorption capacity for several textile dyes. It also forms host-guest relation with aromatic compounds thus removing the toxicity for adsorption. Another mechanism is based on formation of insoluble cucurbitiril dye-cation aggregate as adsorption occurs at a faster rate (Robinson et al., 2001; Nagy et al., 2009) (Fig. 1.1).

5.4 Sodium hypochlorite The process of bleaching can be defined as a method to remove the colors from textile materials by chemically destroying the chromophores present thus increasing

FIGURE 1.1 Structure of cucurbitiril (https://pubchem.ncbi.nlm.nih.gov/compound/Cucurbit_8_uril).

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the brightness of the product. The chloride molecule attacks the amino group of the dye, thus accelerating an azo bonding cleavage. This method is not applied for azo dyes. In an experiment conducted by Massoudinejad et al. it was concluded that combining chemical oxidation method with sodium hypochlorite solution gives relevant standard to biological method. It was also noticed that imported chorine was about 3.65 times more efficient than Iranian native chlorine (Robinson et al., 2001; Massoudinejad et al., 2015).

5.4.1 Ion exchange This is not much widely used process due to the belief that ion exchangers fail to accumulate huge amount of dye particles for removal. Advantage of this method is the no loss of adsorbent molecules (Robinson et al., 2001). Wastewater containing dyes are made to run over the ion-exchange resins until the favorable exchange sites are obtained. One of the major disadvantages of this method is its cost. Organic solvents are costly and disperse dyes cannot be removed using ion exchange method (Anjaneyulu et al., 2005).

5.5 Recent biochemical trend These physicochemical methods are highly applicable to the treatment of textile dye effluents in waste water. But these treatments have certain drawbacks too. For example, intoxicating sludge formation, inefficiency in large scale degradation, too costly to be used for large scale. Thus few recent biochemical trends have been discussed which were found to be effective.

5.5.1 Photocatalysis Photo catalysis can be defined as a process by which a photo reaction is accelerated in the presence of catalyst. This method degrades the dye molecule into water and carbon dioxide by the action of UV rays in the presence of catalyst H2O2. Depending on the product to be catalyzed and the length of the reaction, various byproducts are formed. No sludge production is associated with the process. UV light on degrading reaction with H2O2, forms two hydroxyl radicals which help in the further chemical processes (Robinson et al., 2001). Photo catalytic removals of organic pollutants have been found to be one of the most effective ways. Ag/Cl can be considered as high performing photo catalysts that can be used for degradation. Zhao et al. in his experiment successfully prepared Ag/AgCl nanoparticles biochemically from the metabolin of living fungi. These nanoparticles were found to be 3e5 nm in size, spherical in shape. On studying these particles under microscope it was found that these particles show visible light driven photo catalytic performance. This biochemical invention helped in the degradation of a carcinogenic RhB (Zhao et al., 2015).

6. Advanced oxidation process

6. Advanced oxidation process Oxidation can be defined as one of the efficient methods for the removal of effluents chemically. Usually, in this process the oxidizing agents are activated by some means. Hydrogen peroxide is the most widely used oxidizing agent in this case. Advanced oxidation processes (AOP) can be defined as a set of emerging chemical procedures which can remove soluble organic effluents from water and soil. They use hydroxyl radicals which are powerful oxidants and are nonselective in nature having the power to degrade complex toxic effluents. The complex molecules are usually degraded completely into water and carbon dioxide. The biggest significance of AOP is the simplicity of its usage and production of lesser amount of residuals. Fenton’s method, ozonation, photolysis can also be considered as types of AOPs (Rauf and Ashraf, 2012). As hydroxyl radicals are nonselective in nature thus EAOPs can be coupled with biological processes in pretreatment as well as posttreatment way. Pretreatment is considered when the effluent to be treated as BOD and COD ratio much lower than 0.3 and contains toxic substance which can alter the microbial activities. Thus EAOP is applied to decrease the toxicity level to such a point where biological methods can be applied. Posttreatment is considered when the effluent is mostly filled with biodegradable compounds except for some refractory pollutants. In those cases, cost effective biological method is applied first followed by the application of EAOP to remove the remaining minute toxicity (Ganzenko et al., 2014). Azbar et al. performed a comparative experimental study on various oxidation and chemical treatment methods for effluent and COD removal from polyester and acetate fiber dyeing effluents. He inferred that AOPs have nearly 85% greater success rate in comparison with any other chemical methods for the removal of effluents derived while dyeing polyester and acetate. Among the different AOPs for example O3, O3/UV, H2O2,/UV, the most efficient one is the combined result of ozone, UV and peroxide having removed 99% of COD and 96% color (Azbar et al., 2004). In recent studies, coupling of AOPs has been considered. In simpler words, coupling of AOP can be defined as a method of simultaneous application of more than one AOP in a single step to increase the oxidative strength of the process. Due to the wide number of oxidant production in a step, maximum number of times the process has been considered useful. But there can be instances when due to the excess production of reactive oxygen species (ROS), degradation rate might get reduced (Dewil et al., 2017). Recent trend has suggested that sulfate radical AOPs are gaining a lot of popularity. This can be considered as an advanced alternative to OH- radical AOP. Sulfate radicals have the redox potential from around 2.5e3.1 volt thus making it able to oxidize a wider range of organics. They are pH independent thus organics of any

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CHAPTER 1 A comparative study between physicochemical and biological

pH can be easily oxidized. It has been studied that sulfate radicals are selective in nature thus can be used properly to oxidize specific functional groups responsible for toxicity of wastewater (Lutze et al., 2015).

7. Biological methods Various physicochemical methods such as oxidation, ozonation, membrane technology, coagulation flocculation, and AOPs have been administered to reduce the COD level and to remove the toxic effluents which are released from textile effluents in various water bodies. But these processes have some limitations such as costing, equipments and sludge formation in the end. Many of these processes even work in situ for only small scale effluents. Thus biological methods have been used as alternating techniques to remove large scale effluents using living microorganisms in much cost-efficient and simpler way (Table 1.2).

Table 1.2 Factors affecting biological method of dye removal (Rauf and Ashraf, 2012; Wesenberg et al., 2003). Serial no.

Factor

Affect

1

Oxygen

2

Ph

3

Temperature

4

Dye structure and concentration

5

Redox mediator

Dye degradation can occur under aerobic and anaerobic conditions. Under anaerobic condition, reductive enzyme activity is higher. Under aerobic conditions, carbon sources like glucose, starch, acetate affect the decolorization process. The enzymatic activity depends on the pH and on the acidbase behavior of the substrate and amino acid side chain. The optimum pH for color removal is often neural or slightly alkaline. The rate of color removal decreases with acidic pH values. This is one of the most impactful parameters. With an increase in temperature, the rate of color removal increases too. The temperature required for maximum color removal is nearly around 35 to 45 C, which is also optimum for cell growth. The more dye concentration, the more is the amount of toxicity. Dye structure varies in different dyes. Dyes with simple structure and low molecular weight give out higher rate of color removal and the process is more difficult with dyes of high molecular weight. Enzyme mediated degradation is a versatile process efficient process. The redox mediator is required to maintain the redox equilibrium. The more redox potential, the faster the molecule is reduced.

7. Biological methods

7.1 Degradation with bacteria Aromatic compounds can be degraded biologically under both aerobic and anaerobic conditions. Under aerobic conditions, enzymes like monoazo oxygenase, diazo oxygenase catalyzes the incorporation of oxygen into the aromatic amines prior to ring fission. In maximum monoazo oxygenases, the electro donor is either NADH or NADPH. In presence of azo reductases, few aerobic bacteria are able to reduce azo compounds and produce aromatic amines. Certain aerobic azo reductases, for example, K22 and KF46 strains of Pseudomonas species after undergoing purification and characterization were found to be flavin-free. These azoreductases could use both NADH and NADPH as their cofactors and cleave not only the carboxylated substrate, but also the sulfonated structure (Dos et al., 2007). Reductions of azo dye by bacterial species are usually no specific and bacterial decolorization is a fast process. A wide range of aerobic and anaerobic bacteria have been found beneficial for the degradation purpose, they are Bacillus subtilis, Pseudomonas sp., Escherichia coli, Rhabdobacter sp., Enterococcus sp., Staphylococcus sp, Xenophilussp, Corneybateriumsp, Clostridium sp., Micrococcusdermacoccussp, Acinetobacter sp, Geobacillus, Lactobacillus, Rhizobium, Proteus sp, Morganella sp., Aeromonas sp, Alcaligenes sp., and Klebsiellla sp. Some of the aerobic bacteria use azo dye as the sole source of carbon and nitrogen and others only reduce the azo group by special oxygen-tolerant azo reductases. It has been concluded by various researchers that the complete degradation of the dye requires coupled aerobic-anaerobic degradation. In anaerobic conditions, the azo bond experiences cleavage and aromatic amines are formed. In the aerobic condition, mineralization by nonspecific enzymes through ring cleavage takes place. Thus the coupled treatment can efficiently remove azo dye from wastewater. Pseudomonas sp. can degrade a variety of azo dyes such as Red HE7B, Reactive Blue172, Reactive Red 22, Reactive Red 2, orange I, and II; thus it is the most widely used bacterial strain (Wesenberg et al., 2003). Bacterial degradation can be classified broadly in two ways, using single bacterial cell and using mixed bacterial culture. A strain of Pseudomonas entomophila BS1 was isolated and was used to degrade Reactive Black 5, a kind of azo dye. On 120 h incubation, 93% degradation was found. On making a consortium of P. rettgeri strain HSL1 and Pseudomonas sp. SUK1 to treat certain varieties of azo dye like Reactive Black 5, Reactive orange 16, Direct Red 81, and Disperse Red 78, complete color removal was noticed in microaerophilic, sequential aerobic/ microaerophilic, and microaerophilic/aerobic conditions with minute time differences (Wesenberg et al., 2003).

7.1.1 Immobilization of cells for the degradation of dyes Number of times whole bacterial cells have been used to degrade synthetic dye effluents. There are various bioreactors that have been used for effective continuous treatment aerobic and anaerobic treatment, they are fixed film bioreactors, packed bed bioreactors, aerobic suspended bed activated sludge reactor etc. immobilization

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CHAPTER 1 A comparative study between physicochemical and biological

can be defined as a process which prevents cell washing outs and also allows higher cell density to be maintained in the continuous reactor. Immobilization upgrades the catalytic stability thus increasing the concentration of degradation of textile dyes. It has been studied that immobilization results in increased uptake of nutrients due to the availability of nutrients at the solid-liquid interface. On comparing the immobilized cells of Pseudomonas putinda P8 to the free cells P. putinda, the immobilized cells have been found to be more efficient in degrading catechol. Immobilization method using biomass has been found to be really beneficial. It is performed under aseptic conditions within the bioreactors (Puvaneswari et al., 2006).

7.2 Degradation with algal culture There hasn’t been much advancement in detecting algae for the degradation of textile effluents. Azo reductases can degrade azo dye. Few species of Oscillatoria and Chlorella were able to degrade the azo dye to simpler amines (Banat et al., 1996; Joshi et al., 2004).

7.3 Degradation with yeast Degradation of textile dye effluents by biosorption has been much facilitated by yeast. Yeast has a lot of advantages over bacteria and filamentous fungi. Like bacteria, they can grow fast and also like filamentous fungi they have the ability to resist unfavorable environment. Few yeast species have shown promising result in dye degrading they are Galacto mycesgeotrichum, Saccharomyces cerevisiae and Trichosporonbeigelii, etc. NCIM-3326 could decolorize various azo dyes such as Navy blue HER (100%), Red HE7B (85%), Golden yellow 4BD (60%), Green HE4BD (70%), and Orange HE2R (50%), among which the decolorization rates of some dyes were not desirable (Khan et al., 2013).

7.4 Degradation with fungi Ability to reduce azo dyes by fungi is corelated with the formation of exoenzymes such as peroxidizes and phenoloxidases. Peroxidizes are a kind of hemoproteins catalyzing reacting in presence of hydrogen peroxide. Strains like Bjerkanderaadusta, Trametes versicolor and Phanerochaetechrysosporium were proved to degrade all kinds of azo dyes. Lignin peroxidases were found to oxidize both phenolic and nonphenolic compounds. But, in order to oxidize phenolic compounds, manganese peroxidases have to convert Mn2þ to Mn3þ. Phenol oxidases can catalyze the oxidation of phenolic and nonphenolic aromatic compounds without the help of cofactors. Phenol oxidases are of two types, tyrosinases and laccases (Dos et al., 2007; Imran et al., 2015).

7.5 Degradation with white-rot fungi White-rot fungi are a group of fungi that are capable of degrading lignin biologically. The name white-rot is derived from the white appearance of the wood attacked by

7. Biological methods

WRF, removal of lignin giving it a bleached appearance. Based on taxonomical classification, white-rot fungi are mostly basidiomycete. Exceptionally, few ascomycetes are also capable of white-rot decay. WRF are capable of withstanding a wide range of pH thus being widely capable of degrading toxic pollutants (Asgher et al., 2008). WRF are capable of degrading xenobiotics, lignin and other dye stuffs with their extracellular ligninolytic enzyme system. Few of the extracellular enzymes which helps predominately in biodegradation of dye stuffs are lignin peroxidase (Lip), Mn peroxidase (MnP) and H2O2 dependent peroxidases. Some of the major white-rot fungi strains which are capable of delignification and decolorization are Phanerochaetechrysosporium, Trametes versicolor, and Coriolusversi color. The ligninolytic enzymes are substrate nonspecific in nature, thus can degrade a huge variety of toxic effluents including the complex aromatic pollutants (Kapdan et al., 2000). Initially, to assay the lignolytic activity of WRF, sulfonated polymeric dyes were used. Eventually, a number of WRF strains were used to decolorize distinctive synthetic dyes. In comparison with prokaryotes, WRF are superior dye decolorizers. Even, in comparison with P. chrysosporium, the lignin transforming actinomycete Streptomyces chromofuscus is a weak decolorizing microbial strain (Wesenberg et al., 2003).

7.6 Enzyme system of white-rot fungi Lignin metabolizing enzymes (LMEs) are essential for lignin degradation. Few of the major LMEs which are involved in the degradation of lignin and xenobiotics are lignin peroxidase, Manganese peroxidase, laccase and versatile peroxidase. Other than these, there are few accessory enzymes which are isolated from certain WRF strains, they are H2O2-forming glyoxal oxidase, aryl alcohol oxidase, oxalate producing oxalate decarboxylase (ODC), NAD-dependent formate dehydrogenase (FDH) and P450 monooxygenase. WRF produces LMEs during secondary metabolism as lignin oxidation yields no net energy to the fungus (Wesenberg et al., 2003; Asgher et al., 2008).

7.6.1 Lignin peroxidase (LiPs) These are capable of mineralizing a wide range of aromatic compounds. The molecular mass of various white-rot fungi strain varies from 37 to 50 kDa. It has been noticed that immobilizing Lip has significantly increased its optimum temperature, thermo stability as well as catalytic properties. Oxidation by Lip depends on the optimum molar ratio of H2O2 to pollutant. At lower concentration, H2O2 acts as an activator of Phanerochaete chrysosporium LiP and at higher concentration it acts as an inhibitor rapidly deactivating the enzyme (Asgher et al., 2008).

7.6.2 Manganese peroxidase (MnPs) This is one of the most common peroxidase produced by almost all white-rot fungi and few litter decomposing fungi. They are extra cellular glycoprotein having iron protoporphyrin IX prosthetic group with a molecular weight of around 32 and

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CHAPTER 1 A comparative study between physicochemical and biological

62.5 kDa. They are secreted in multiple isoforms. MnPs generally oxidize Mn2þ to Mn3þ which then is stabilized by chelating compound such as oxalic acid which is also secreted by the fungi itself. The chelated Mn3þ thus formed is highly reactive and acts as a diffusible redox mediator. Thus, MnPs oxidizes and depolymerizes lignin and also xenobiotics like nitroaminotoluenes and toxic textile dyes. The stability of MnP can be enhanced by immobilizing with sodium alginate, gelatin or chitosan as carriers and glutaraldehyde as cross-linking (Wesenberg et al., 2003; Asgher et al., 2008).

7.6.3 Laccases These are N-glycosylated extracellular blue multicopper oxidases having molecular mass around 58e90 kDa. The optimum pH and temperature vary from around 2 to 10 and 40e65 C respectively. Two strains of laccase isoenzymes LacI and LacII have been found in Physisporinus rivulosus T241i, Trametestrogii, Cerrena unicolor 137 and Panustigrinus. Laccases along with oxidizing aphenolic and methoxyphenolic acids, it also decarboxylizes them and attacks their methoxy groups (Asgher et al., 2008). Small molecule mediators are low molecular weight highly diffusible redox substances which help in the interaction between lignin and LME. Due to the random polymer nature of lignin and bulk of LME, the interaction becomes highly problematic thus these mediators come in action. A few examples of native mediators are P. chrysosporium, Armillaria mellea, and so forth (Wesenberg et al., 2003). Most of the dye stuffs that are used in the industries are extensively harmful to any living being. These dye effluents are highly carcinogenic in nature. White-rot fungi are used for the purpose of degradation of these harmful dye effluents. White-rot fungi are preferred over prokaryotic cells due to the presence of LME system which is nonspecific in nature, thus can degrade a wide range of dyes. P. chrysosporium and Trametes versicolor are the most used ones. There are other useful WRF too, they are Phellinus gilvus. DIchomitussqualens. Irpex flavus, Ganoderma sp., etc. The degrading mechanism of dyes varies from the structure and reactivity of different dyes. For instance, the decolorization of Reactive Blue 15 by chrysosporium follows first order kinetics with respect to initial dye concentration. Here, MnP plays a major role in decolorization (Asgher et al., 2008). In an experiment conducted by Kapdan et al. he prepared four separate white-rot fungi cultures to decolorize five kinds of textile dyes. The strains of white-rot fungi taken were P. chrysosporium MUCL, P. chrysosporium 671.71, Coriolus versicolor MUCL, and C. versicolor. The dye stuffs taken were Everzol Yellow 4 GL (Reactivemonoazo), Everzol Red RBN (Reactive-monoazo), Drimaren Orange K-GL (Reactive-disazo), Everdirect Supra Yellow PG (Direct-disazo) and Everzol Turquoise Blue G (Reactive-phtalocyanin). He concluded that the culture of P. chrysosporium or C. versicolor were highly effective in total removal of dye color effluents. But, the high incubation temperature around 37 C was marked to be disadvantage for the process. Because of lower incubation temperature around 28 C requirement for C. versicolor cultures, C. versicolor MUCL culture seems to be more suitable than P. chrysosporium culture for practical applications (Kapdan et al., 2000).

References

8. Conclusion Different textile industries generate different forms of textile dyes. In this research article, various physicochemical methods, their advantages and limitations, and various biological processes with their advantages, have been discussed (Bhatia et al., 2017). The various physicochemical methods were found to be costly and reactive only when the effluent volume was less. Many of these processes produced large volumes of sludge in the end thus not being effective in removal of toxicity (Ramachandran et al., 2013). Due to the ineffectiveness of the conventional physicochemical processes, biological processes have been discussed which were considered to be more ecofriendly and effective for the removal of textile dyes (Ramachandran et al., 2013). Bioremediation methods use naturally occurring microbes which are economically friendly and even cost-efficient. Processes like biosorption is an amalgamation of physical and biological method has been discussed as an emerging technique which can be used to degrade textile effluent (Bhatia et al., 2017).

References Anis, S.F., Raed, H., Nidal, H., 2019. Microfiltration membrane processes: a review of research trends over the past decade. J. Water Process Eng. 32, 100941. Anjaneyulu, Y., Sreedhara Chary, N., Samuel Suman Raj, D., 2005. Decolourization of industrial effluents e available methods and emerging technologies e a review. Rev. Environ. Sci. Biotechnol. 4 (4), 245e273. Asgher, M., Bhatti, H.N., Ashraf, M., Legge, R.L., 2008. Recent developments in biodegradation of industrial pollutants by white rot fungi and their enzyme system. Biodegradation 19 (6), 771. _ Yonar, T., Kestioglu, K., 2004. Comparison of various advanced oxidation Azbar, N.U.R.I., processes and chemical treatment methods for COD and color removal from a polyester and acetate fiber dyeing effluent. Chemosphere 55 (1), 35e43. Banat, I.M., Nigam, P., Singh, D., Marchant, R., 1996. Microbial decolorization of textiledyecontaining effluents: a review. Bioresour. Technol. 58 (3), 217e227. Benkhaya, S., Mrabet, S., Ahmed, El H., 2020. A review on classifications, recent synthesis and applications of textile dyes. Inorg. Chem. Commun. 107891. Bhatia, D., Sharma, N.R., Singh, J., Kanwar, R.S., 2017. Biological methods for textile dye removal from wastewater: a review. Crit. Rev. Environ. Sci. Technol. 47 (19), 1836e1876. Buckley, C.A., 1992. Membrane technology for the treatment of dyehouse effluents. Water Sci. Technol. 25 (10), 203e209. Dewil, R., DionissiosMantzavinos, I.P., Rodrigo, M.A., 2017. New perspectives for advanced oxidation processes. J. Environ. Manag. 195, 93e99. Dos, S., Andre´, B., Cervantes, F.J., van Lier, J.B., 2007. Review paper on current technologies for decolourisation of textile wastewaters: perspectives for anaerobic biotechnology. Bioresour. Technol. 98 (12), 2369e2385. El Harfi, S., El Harfi, A., 2017. Classifications, properties and applications of textile dyes: a review. App. J. Environ. Eng. Sci. 3 (3), 00000e00003.

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Ganzenko, O., Huguenot, D., Van Hullebusch, E.D., Esposito, G., Oturan, M.A., 2014. Electrochemical advanced oxidation and biological processes for wastewater treatment: a review of the combined approaches. Environ. Sci. Pollut. Control Ser. 21 (14), 8493e8524. Imran, M., Crowley, D.E., Khalid, A., Hussain, S., Mumtaz, M.W., Arshad, M., 2015. Microbial biotechnology for decolorization of textile wastewaters. Rev. Environ. Sci. Biotechnol. 14 (no. 1), 73e92. Joshi, M., Bansal, R., RengPurwar, 2004. Colour Removal from Textile Effluents. Kapdan, I., Kargi, F., McMullan, G., Roger, M., 2000. Comparison of white-rot fungi cultures for decolorization of textile dyestuffs. Bioprocess Eng. 22 (4), 347e351. Khan, N.A., et al., 2020. Recent Trends in Disposal and Treatment Technologies of EmergingPollutants- A Critical Review. Khan, R., Bhawana, P., Fulekar, M.H., 2013. Microbial decolorization and degradation of synthetic dyes: a review. Rev. Environ. Sci. Biotechnol. 12 (1), 75e97. Lahkimi, A., Oturan, M.A., Oturan, N., Chaouch, M., 2007. Removal of textile dyes from water by the electro-Fenton process. Environ. Chem. Lett. 5 (1), 35e39. Lin, S.H., Lin, C.M., 1993. Treatment of textile waste effluents by ozonation and chemical coagulation. Water Res. 27 (12), 1743e1748. Lutze, H.V., Kerlin, N., Schmidt, T.C., 2015. Sulfate radical-based water treatment in presence of chloride: formation of chlorate, inter-conversion of sulfate radicals into hydroxyl radicals and influence of bicarbonate. Water Res. 72, 349e360. Malaeb, L., Ayoub, G.M., 2011. Reverse osmosis technology for water treatment: state of the art review. Desalination 267 (1), 1e8. Massoudinejad, M., Ghaderpoori, M., Rezazadeh Azari, M., 2015. The removal of COD and color from textile industry by chlorine hypochlorite. Int. J. Adv. Sci. Technol. 76, 35e42. Nagy, H.J., Pe´terSallay, M.L.V., Istva´nRuszna´k, P.B., Andra´s, V., 2009. Removal of dyes from industrial wastewater by cucurbiturils. Textil. Res. J. 79 (14), 1312e1318. Natarajan, S., Hari, C., Bajaj, Tayade, R.J., 2018. Recent advances based on the synergetic effect of adsorption for removal of dyes from waste water using photocatalytic process. J. Environ. Sci. 65, 201e222. Nemr, A.E.L., 2012. Non-Conventional Textile Waste Water Treatment. Nova Science Publishers. Nguyen, T.A., Ruey-Shin, J., 2013. Treatment of waters and wastewaters containing sulfur dyes: a review. Chem. Eng. J. 219, 109e117. Panizza, M., Cerisola, G., 2001. Removal of organic pollutants from industrial wastewater by electrogenerated Fenton’s reagent. Water Res. 35 (16), 3987e3992. Pa
zdzior, K., Klepacz-Smo´1ka, A., Ledakowicz, S., So´jka-Ledakowicz, J., Mrozi
nska, Z., _ Zy11a, R., 2009. Integration of nanofiltration and biological degradation of textile wastewater containing azo dye. Chemosphere 75 (2), 250e255. Porter, J.J., 1973. The stability of acid, basic, and direct dyes to light and water. Textil. Res. J. 43 (12), 735e744. Puvaneswari, N., Muthukrishnan, J., Gunasekaran, P., 2006. Toxicity Assessment and Microbial Degradation of Azo Dyes. Ramachandran, P., Rajakumar, S., Palaniyappan, J., Ayyasamy, P.M., 2013. Potential process implicated in bioremediation of textile effluents: a review. Adv. Appl. Sci. Res. 4 (no. 1), 131e145. Rauf, M.A., Ashraf, S.S., 2012. Survey of recent trends in biochemically assisted degradation of dyes. Chem. Eng. J. 209, 520e530.

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Robinson, T., McMullan, G., Marchant, R., Nigam, P., 2001. Remediation of dyes in textile effluent: a critical review on current treatment technologies with a proposed alternative. Bioresour. Technol. 77 (3), 247e255. Saini, R.D., 2017. Textile organic dyes: polluting effects and elimination methods from textile waste water. Int. J. Chem. Eng. Res. 9, 121e136. Singh, K., Arora, S., 2011. Removal of synthetic textile dyes from wastewaters: a critical review on present treatment technologies. Crit. Rev. Environ. Sci. Technol. 41 (9), 807e878. Singh, P.K., Ram, L.S., 2017. Bio-removal of azo dyes: a review. Int. J. Appl. Sci. Biotechnol. 5 (2), 108e126. Sulak, M.T., Cengiz Yatmaz, H., 2012. Removal of textile dyes from aqueous solutions with eco-friendly biosorbent. Desalination Water Treat. 37 (1e3), 169e177. Vanitha, K., Kansedo, J., Lau, S.Y., 2018. Efficiency of various recent wastewater dye removal methods: a review. J. Environ. Chem. Eng. 6 (4), 4676e4697. Verma, A.K., Rajesh, R.D., Puspendu, B., 2012. A review on chemical coagulation/flocculation technologies for removal of colour from textile wastewaters. J. Environ. Manag. 93 (1), 154e168. Wesenberg, D., Irene, K., Agathos, S.N., 2003. White-rot fungi and their enzymes for the treatment of industrial dye effluents. Biotechnol. Adv. 22 (1e2), 161e187. Xu, Y., Lebrun, R.E., 1999. Pierre-Jean Gallo, and Pierre Blond. "Treatment of textile dye plant effluent by nanofiltration membrane. Separ. Sci. Technol. 34 (13), 2501e2519. Yang, C.-L., McGarrahan, J., 2005. Electrochemical coagulation for textile effluent decolorization. J. Hazard Mater. 127 (1e3), 40e47. Zhao, X., Zhang, J., Wang, B., Amir Zada, Humayun, M., 2015. Biochemical synthesis of Ag/ AgCl nanoparticles for visible-light-driven photocatalytic removal of colored dyes. Materials 8 (5), 2043e2053. _ Zy11a, R., Jadwiga, S.-L., Ewa, S., Stanis1aw, L., 2006. Coupling of membrane filtration with biological methods for textile wastewater treatment. Desalination 198 (1e3), 316e325.

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CHAPTER

An approach toward developing clean green techniques to deal with heavy metal toxicity using the microbiome

2

Subhasish Dutta, Pitam Chakrabarti Department of Biotechnology, Haldia Institute of Technology, Haldia, West Bengal, India

1. Introduction Environmental pollution is a very pressing problem today. This has resulted in an acute crisis in the availability of clean water and soil for the production of crops and other necessities. Heavy metal toxicity is one of the major symptoms of this problem. Heavy metals are classified as a group of metals that have a density greater than 4000 kg/m3, which is roughly five times heavier than air. Heavy metal toxicity occurs due to the excess accumulation of heavy metals in the environment. These metals are extremely toxic in their ionic states, and when they react with the biomolecules present in the body, they form very stable biotoxic substances. In recent years there has been an increased concern regarding public health due to this problem. Rapid Industrialization and improper waste treatment have ensured that there is a constant influx of poisonous heavy metals into the environment. Sources of such pollutants include industries, pharmaceutical companies, and domestic effluent (Kulshreshtha et al., 2014; Tchounwou et al., 2012) (Fig. 2.1). Although some heavy metals are necessary, they are involved in several biophysical and biochemical activities, and even take part in key enzymatic reactions. For example, copper is a component of many enzymes such as catalase and superoxide dismutase. The ability of copper to exchange between its two oxidative states is another property that is involved in many redox reactions. However, when excessive exposure to copper occurs, cellular damage happens. This condition is diagnosed with Wilson’s disease. Similarly, chromium in large amounts is very harmful. Heavy metals are deadly in biological systems. They have been reported to affect the mitochondria, lysosome, endoplasmic reticulum, and other cellular organelles. Metal ions also generate DNA damage and some can even prove to be carcinogenic (Tchounwou et al., 2012). Toxicity of nonessential metals like cadmium, gold, lead, and mercury happens when they dislodge essential metals from their binding Development in Wastewater Treatment Research and Processes. https://doi.org/10.1016/B978-0-323-85657-7.00004-3 Copyright © 2022 Elsevier Inc. All rights reserved.

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CHAPTER 2 An approach toward developing clean green techniques

Mining of metals from earth

Extrac on of metal from ores

Produc on processes

Wastes

Residues, Effluents, Debris

Soil/Landfills, Freshwateraa

FIGURE 2.1 Pathway by which heavy metals make their way into the environment.

sites. For example, higher oxidative states of mercury and cadmium can attach to specific protein groups such as the SH group. This stops the activity of these enzymes. Impacts of heavy metal toxicity are not always easily detected. In the majority of the cases, there will be a decrease in the biological activity of the soil. Also in some cases, there might be an increase in the proportion of fungi such as actinomyces. The contamination of the food chain also occurs due to heavy metal pollution (Mohammed et al., 2011). Bioremediation can be applied as a way to deal with these contaminants. Over the years many other methods such as physical, chemical, and thermal processes have been employed; but there have been serious drawbacks in many cases. Rather than remediating the ecosystem, it was just replacing old problems with new ones. Bioremediation on the other hand employs biological systems and microorganisms, and can be used as a clean green technique. Bioremediation is defined as a process by which organic wastes can be degraded when subjected to specific conditions from high levels to concentrations below the danger limit. Bioremediation using microorganisms harnesses their enzymatic mechanisms to transform the toxic substances into less hazardous or nonhazardous materials. Bioremediation can be classified into two types depending upon the site of action. Insitu bioremediation, where the treatment occurs at the place of the contamination, and ex-situ bioremediation, where the pollutants are transported to the laboratory for treatment (Arora, 2018). In-situ bioremediation takes place for the treatment of heavy metals. Here we shall see how we can harness this to be used as clean green technology.

2. Different heavy metals and their impacts 2.1 Arsenic Arsenic is one of the most commonly found heavy metals in almost every environment. It is most commonly found inorganic forms are pentavalent arsenate and the

2. Different heavy metals and their impacts

trivalent arsenite. In the organic form, it is found in methylated metabolites. Arsenicbased compounds are still used for treating many diseases; for example the African sleeping sickness. Compounds based on arsenic are produced and are used for manufacturing different products for killing insects and also as pesticides. Yearly several million people are subjected to arsenic exposure in many countries. The trivalent arsenite is 10 times more toxic than pentavalent arsenate. Intake of arsenic occurs orally or even through the skin. Exposure to it at high levels is a concern because it can cause severe health issues. It affects virtually all the organ systems including cardiovascular and even the nerves. Understanding the harmful effects of arsenic is very tough because of the influence of its oxidation states and their solubility. Most cases arise due to exposure to inorganic arsenic (Rehman et al., 2018).

2.2 Cadmium Cadmium is another heavy metal that is frequently found in ores. It is also one of the major components of some fertilizers and is generally used as a stabilizer in coloring pigments. Environmental contamination of cadmium is a severe problem and occurs rampantly. Indiscriminant dumping of sewage sludge and burning of wastes causes soil contamination. The application of phosphate fertilizers into the fields also causes cadmium to enter the food chain through the crops. Once cadmium enters the body it combines with various proteins and enters the gastrointestinal tract. Then it enters the liver and produces a metal complex that gets released into the sinusoidal blood. Cadmium poisoning can occur over a large period and can eventually lead to tubular necrosis. Cadmium contamination causes neurotoxic disorders. Increased doses of cadmium in drinking water can lead to kidney damage and are lethal for diabetic patients. Recent researches have also exposed that it is a potent carcinogen and can cause breast cancer (Rehman et al., 2018).

2.3 Lead Lead is found frequently in the earth’s layers. It has numerous applications in agriculture as well as in industries. Exposure to lead has been increasing rapidly because of several human activities. Mining, burning of fossil fuels contribute severely to lead exposure. The main routes by which lead enters the human body are ingestion by food, via drinking water, or inhalation in the form of aerosols. Surveys conducted reveal that 35%e50% of lead toxicity happens through contaminated drinking water. Once lead enters our body, it gets incorporated into minerals instead of calcium. It diminishes the activity of various enzymes and causes oxidative stress. Research also revealed that workers exposed to lead have increased activity of glucose-6-phosphate dehydrogenase, and it also disrupts the membrane of Red Blood Cells (RBCs) and causes cell fragility. Exposure to lead regularly has a severe impact on human health. It causes damage to the cognitive area of the brain and hampers reading and speech. The pronounced neurotoxic effects, cardiovascular damage, infertility, and hemolytic anemia, as well as vitamin D deficiency, are some other side effects of lead toxicity (Rehman et al., 2018).

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2.4 Nickel Nickel is the 24th most abundant metal. Due to the recent increase in industrialization, there has been increments introduced in environmental pollutants, and nickel has become a hazardous contaminant. Although nickel is a micronutrient, in elevated amounts it can cause severe illness. Nickel exposure occurs mainly by two pathways: through our food and our drinking water. Tobacco smoke is one of the major sources of nickel along with coal combustion and waste incineration. Nickel is also used for electroplating, and during this process, they become a part of industrial emission. Upon entering our body nickel forms stable biotoxic complexes that reduce enzymatic action. Nickel binds with sulfhydryl proteins and reduces glutathione levels. Exposure to nickel over a long duration of time can also lead to allergic reactions. Nickel also degenerates liver tissues, damages the lungs, and also the kidneys. It is also a potent carcinogen (Rehman et al., 2018).

2.5 Mercury The major sources of mercury poisoning occur from the mining of gold and the combustion of coal. Environmental contamination also occurs due to cement production, municipal and medical wastes, and also fertilizers. Case histories of the Minamata disease and Niigata disease are famous. These were caused due to the release of methyl mercury into the bay area. When inhaled mercury easily enters the respiratory system and oxidizes to form Hg (II). Then it enters the circulatory system. The primary organs of poisoning are the brain and the kidney. Mercury can easily traverse the blood-brain barrier and cause neurological disorders. Continuous exposure to mercury causes severe pneumonitis and acute necrotizing bronchitis. Additional symptoms include immune dysfunction, weight loss, and gastrointestinal disturbance. Hg(II) however passes the blood-brain barrier and has sufficiently less impact on the brain. Organic mercury affects the central nervous system and it is the main part of the body, where mercury poisoning can occur severely. In the brain, it produces high oxidative stress (Rahman and Singh, 2019) (Table 2.1).

2.6 Copper Unlike many other heavy metals, copper is an important micronutrient that is necessary for plants as well as animals. Although in large amounts it has adverse health effects. Copper (Cu (II)) in high amounts leads to anemia and severe damage to the kidney and liver. Irritation in the stomach and problems in the central nervous system are also another tell-tale sign of copper toxicity (Majumder et al., 2015).

2.7 Chromium Chromium is primarily found in ores in the form of chromite. It plays an essential role in the metabolism of both plants and animals; however, in higher amounts, it proves to be toxic. Occupational hazards expose people to chromium. Although

2. Different heavy metals and their impacts

Table 2.1 List of heavy metals and their sources. Heavy metal Arsenic

Nickel

Exposure

Major sources

Health problems

References

Ingestion through drinking water, food, and occupational hazards Inhalation, ingestion through drinking water, food

Smelting, industrial wastes, pesticides

Cardiovascular diseases, carcinogenesis, decreased mental performance Damage to kidney tissues, liver, and the lungs

Rehman et al. (2018)

Cadmium

Ingestion through drinking water, food

Lead

Ingestion of contaminated water, inhalation of aerosols Inhalation of contaminated air, and ingestion of water and food Ingestion through food or water

Mercury

Copper

Chromium

Ingestion through food and water

Chemical industries, tobacco smoke, electroplating Indiscriminate incineration, fertilizers, cigarette smoking Mining, burning of fossil fuels, manufacturing of paint Mining of gold, cement production, municipal and medical wastes Municipal wastes, mining, industrial hazards

Industrial hazards, mining

Breast cancer, neurotoxic disorders, tubular necrosis, kidney damage Decreased memory, cardiovascular damage, infertility, hemolytic anemia Immune dysfunction, weight loss, gastrointestinal disturbance Irritation in the stomach and liver, damage to the kidney, and problems in the central nervous system Neurological disorders, ulcers, and deformations

Rehman et al. (2018)

Rehman et al. (2018)

Rehman et al. (2018)

Rahman and Singh (2019)

Majumder et al. (2015)

Ray and Ray (2009)

Cr(III) is not readily absorbed, Cr(VI) is much more stable and gets deposited in major body organs. Respiratory and dermal problems were already reported, however neurological disorders, ulcers, deformations are also occurring due to chromium toxicity. Although Cr(VI) may be weakly carcinogenic to the lungs, however, it proves to be deadly when ingested (Ray and Ray, 2009).

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3. Bioremediation: the savior of the environment 3.1 Biosorption Rapid industrialization has resulted in high levels of contamination in the environment. Bioremediation could serve as a novel technique to reduce this problem. The microbiome can remove heavy metals by either, biosorption or bioaccumulation. Biosorption is energy independent process by which the microbes bind the negatively charged components to the cell wall. Biosorption of hexavalent chromium by dead biomass of Aeromonas caviae was recently observed and recovery of Cadmium by Actinomycetes was also previously observed. Further studies revealed the presence of even more bacterial species with a greater affinity toward heavy metals such as cadmium (Zouboulis et al., 2004). Due to the small size of the biomass and certain other physical characteristics, problems occurred. So to implement it more effectively a search for an immobilization matrix was started. Loofa sponges were an ideal immobilization matrix. These were fibrous and derived from the dry fruit of Luffa cylindrica. Earlier studies had already discovered that using loofah sponge as an immobilization matrix Chlorella sorkiniana could adsorb heavy metals effectively (Akhtar et al., 2004).

3.1.1 Biosorption by bacteria A methodical study was carried out step by step. First, soil samples were collected from different areas. Then they were analyzed accordingly. Identification of the different, microorganisms was performed and then they were isolated. The screening test was then conducted to remove bivalent cadmium and hexavalent chromium from the solutions. The appropriate consortia of microorganisms were then grown in Luria Bertani broth at 28 C and pH 7. The cell biomass was segregated by centrifuging it at 4500 RPM for 10 min, and then they were washed using 0.9% NaCl solution. Then the thermal treatment was given and they were stored at 4 C. An aqueous solution of metal slats were prepared and added to the biological suspension and the pH was then accordingly adjusted (Zouboulis et al., 2004). It was seen that Bacillus laterosporus and Bacillus licheniformis were among the two most dominant strains of bacteria that were isolated. Then the bacterial strains were subjected to different concentrations of toxic metal to develop a metal adsorption isotherm. The biosorption capacity was observed. It was optimal for nonliving cells of both the bacterial strains. The biosorption capacities for the removal of both bivalent cadmium and hexavalent chromium were observed. It was deemed to be an economically attractive and effective treatment (Zouboulis et al., 2004). Some of the bacterial species known to have heavy metal remediation capacities are depicted here (Table 2.2). Among the microbial population, fungi have been observed to be able to immobilize heavy metals. They form insoluble metal oxalate onto polymers which can then be removed. Various studies have suggested that using fungi as potential biosorbents instead of bacteria might prove to be more advantageous. Many Agaric

3. Bioremediation: the savior of the environment

Table 2.2 List of some bacteria displaying heavy metal remediation capacities. Bacterial species

Property

References

Aeromonas caviae Actinomycetes Spirulina Bacillus licheniformis Bacillus laterosporus Acinetobacter guillouiae Bacillus firmus Staphylococcus sp Micrococcus sp Acinetobacter sp

Cr(VI) resistant Cd resistant Pb resistant Cd(II) resistant Cr(VI) resistant Cu resistant Cu resistant Pb resistant Ni resistant Ni resistant

Akhtar et al. (2004) Akhtar et al. (2004) Chen and Pan (2005) Zouboulis et al. (2004) Zouboulis et al. (2004) Majumder et al. (2015) Salehizadeh and Shojaosadati (2003) Kumar et al. (2011) Congeevaram et al. (2007) Bhattacharya and Gupta (2013)

fungal species could be used as biosorbents for heavy metal removal. Mushrooms grow all around the world and have all the required properties for biosorption. However, the heavy metal biosorption capabilities are yet to be assessed except for a few species such as Agaricales, Tremera fuciformis, and Auricularia polytricha. These are more commonly known as jelly fungi. They derive their name because of the presence of water-absorbing polysaccharides. Their morphological structures suggest that they could serve as biosorbents for treating heavy metal toxicity in water bodies (Pan et al., 2010). Also, fungal strains belonging to Zygomycetes having high chitin and chitosan are apt biosorbents. Dead fungal biomass is very advantageous because they are inexpensive. The surfaces of these cells are negatively charged due to anionic structures. So they can bind to metal cations (Gavrilescu, 2004).

3.1.2 Biosorption by fungi Dried up fruiting bodies of Tremera fuciformis, and Auricularia polytricha were gathered and immersed in deionized water to obtain humid jelly fungi. Then four different types of biosorbents were prepared. The same amount of the fungi was used in all the cases (dried red ear, humid red ear, dried silver ear, and humid silver ear). A stock solution of 1000 mg/L of metals was prepared by dissolving metal salts in deionized water. Then the biosorption experiments were carried out. For each experiment, a 100 mL Erlenmeyer flask was taken and to it, a fixed amount of the biosorbent was added. Then 25 mL of the stock solution was added to it and it was then placed on a rotary shaker at 150 RPMs at 25 C. The time intervals were set according to the types of metal solution used. After completion, the fungal biomass was segregated and obtained using filtration. It was then dried at 80 C for 12 h. Then the filtrate was digested in 67% HNO3 and then by 0.1 M HCl. Then the metal concentrations were measured (Pan et al., 2010).

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The biosorption reached equilibrium after 30 min of the experiment. It was seen that the four biosorbents displayed a higher amount of adsorption rate towards the lead, as compared to cadmium or other metals. The biosorbent property of a humid silver ear was also far greater than that of the dry silver ear. The fruiting bodies of the fungi which were used showed a marked observation when they were used in a multi-metal solution. The pseudofirst-order kinetic model was employed to justify the experimental data (Pan et al., 2010).

3.2 Bioaugmentation: a new green technology 3.2.1 Microbial bioaugmentation The technique of bioaugmentation has been around for many years. It has been applied in agriculture where symbiotic nitrogen-fixing bacteria were inoculated in legumes. More recently it has been applied in other areas to enhance the rate of remediation of numerous environmental problems. In certain places, the continuous addition of metal contaminants and other pollutants decreases the microbial activity of the soil. This problem mainly arises due to the cocontamination of the soil which poses stress upon the microbes. Bioaugmentation involves the addition of specific microbes which enhances the activity of the existing microbial populations (Pepper et al., 2002). Around the world municipal waste forms a major part of the landfill. The leachate produced from these waste proves detrimental to the soil. The leachate often contains a mixture of heavy metals like cadmium, nickel, chromium, lead, and mercury. When they seep deeper into the soil, it causes the soil to become toxic and leads to heavy metal pollution. Remediation technologies are often very costly and are commercially limited to developed nations. Hence to develop a clean green technology that could be user friendly and also cost-effective, bioaugmentation was chosen (Emenike et al., 2017). A systemic study was conducted to find out more about such microbes. Soil samples were collected from two sources. One was from a landfill and the other was from a noncontaminated location. A portion of the soil was then removed to measure the metal concentration present. To find out about the possible nature of the microbes, plating was done. About 1 g of the sample soil was taken and it was dissolved in 0.9% NaCl solution. Then it was agitated for 2 h at 150 RPMs. Then they were plated on nutrient agar dishes and incubated for 2 days at optimum temperatures. After that pure cultures were obtained and they were then recognized through specific protocols. A total of nine separate strains of bacteria were isolated from the soil. Then three separate preparations each containing 10% v/w was prepared. The composition was maintained as leachate to the noncontaminated soil. The first preparation contained all nine strains of bacteria (LSA), the second preparation contained three strains of bacteria (LSB), and in the third, no microbes were inoculated. Then consecutive assessment was performed upon them on every 20th day for 100 days (Emenike et al., 2017). The different strains of the microorganisms which were isolated were found, to contain both Gram-positive and Gram-negative bacteria. The soil sample, which was

3. Bioremediation: the savior of the environment

collected from the landfill, was also seen to be enriched with lead and cadmium. After they were subjected to experimental conditions for 100 days certain observations were made. The LSA and LSB treatments, respectively, were seen to contain lower residual concentrations of the heavy metals. However, despite the higher microbial concentration in LSA, LSB was seen to have a greater remediation capacity. Further studies revealed that the best result was obtained when two bacterial species Lycinibacillus and Rhodococcus were involved. Furthermore, a peculiar observation was made. Pseudomonas, Brevundimonas, Stenotrophomonas have a high binding capacity for Cu(II). These work together and enhance metal removal from a system (Emenike et al., 2017).

3.3 Phytoremediation Phytoremediation is a rapidly emerging field of technology that harnesses the power of plants and its symbiotic association with microbial populations to help in the remediation of the environment. It provides a separate and much cleaner technology to that of the chemical amendments. Novel applications of these microbes have opened up new avenues in the sectors of metal detoxification. Phytoextraction is one of the major elements of phytoremediation. It involves specialized plants that can accumulate heavy metals to remove metal from the soil by storing them in the harvestable parts of the plant. Phytostabilization is also another process of phytoremediation and it is deemed to be highly successful. These plants use their dense mass of roots and plant-associated rhizosphere microbes to prevent the metals from leaching through the soil. Plants growing in metal-contaminated soil sustain a large diversity of microorganisms. These microbes can tolerate high concentrations of metal and in turn, provide several benefits to the plant and the soil. Among these microorganisms, rhizosphere bacteria play a special role. They can aid in bioremediation by affecting metal bioavailability by changing the soil pH and by using chelators (Rajkumar et al., 2012).

3.3.1 Rhizoremediation Rhizoremediation is a form of bioremediation that harnesses two different methodologies, phytoremediation and bioaugmentation. The term rhizosphere was first coined by Hiltner in 1904. It means the portion of soil present directly under the root; an interface comprising of the plant roots, the rhizosphere microbes, and the soil. The large microbial population sustained by the plant roots serves as a kind of defense system to the plants by killing pathogens and helping them to survive in contaminated as well as noncontaminated soil. The colonization of the microorganisms in turn helps them to move deeper into the soil and detoxify the contaminants. Rhizoremediation is hence a very attractive process. It allows a large population of microbes over a large surface area and transports them deeper into the soil. To have an optimum activity the selection of correct microbial populations

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is thus essential with proper growth-promoting activities. Heavy metals in high concentration can damage cells by causing them, oxidative stress. However many microbes have adapted by duplicating their transport systems.

3.3.1.1 Mechanisms of metal resistance One of the major heavy metals is arsenic and the mechanism of arsenate remediation is quite widespread within the microbes. Arsenic enters the cell via the phosphate transporters. However, arsenic can only be transported as As(III) and not As(V) thus an enzyme arsenic reductase catalyzes the reduction of As(V) to As(III). S. Meliloti shows arsenic resistance; however, it is much weaker as compared to Ochrobactrum and Pseudomonas. The arsenic resistant operon of S. Meliloti was seen to be composed of four genes and recently, these were seen to be widely distributed among various other species such as S fredii, and Vigna mungo. Cadmium resistance in rhizobium strains was also reported. These bacteria used various efflux techniques to get rid of the cadmium. Ralstonia metalliudurans was reported to use a polypeptide chemiosmotic efflux system. Nickel resistance was also depicted by Bradyrhizobium strains. Serianthes calcyna was also reported to have nickel resistance (Pajuelo et al., 2011).

3.4 Mycoremediation, erasing environmental pollutants The continuous and prolonged industrial exploitation has resulted in severe implications for the environment. Mycoremediation is proving as a cost-effective and efficient technique to battle against this problem. Mechanisms such as chelation and attaching to the cell wall and intracellular mechanism are some proposed ways for heavy metal tolerance. Biosorbent preparation from mushroom fruiting bodies was done. It was seen to be influenced by many factors such as temperature, presence of metal ions, and ph. The basic structural features of fungi favor them to act as heavy metal removers. The chitin present helps them to survive high metal concentrations and fungi can also survive in low pH conditions. So they are a good choice as mycoremediants (Kapahi and Sachdeva, 2017). Further studies were thus conducted to gain more insight into fungal strains that promote mycoremediation. Soil samples were collected from various industrial hotspots. They were then dried for 2 weeks and then subjected to tests. The heavy metal concentrations in the soil samples were measured. About 0.5 g of the soil sample was taken and added to the flask, then 5 mL of nitric acid was added and it was incubated overnight. Then the next day perchloric acid was added and it was heated at 60 C overnight. The solution was then diluted over several ranges and subjected to spectrophotometry and the heavy metal concentrations were determined. Then the segregation of the fungal strains having high uptake efficiency was carried out. The colony morphologies were also analyzed by plating them in specific mediums. To check the bioleaching capacities of these colonies they were further grown in three different types of media, yeast peptone glucose (YPG), Czapek yeast extract (CYE), and Sabouraud dextrose broth (SDB). After an incubation time of 72 h for each medium, a portion was transferred to a falcon tube and it was centrifuged at 4500 RPM for 15 min, and the supernatant was subjected to analysis.

3. Bioremediation: the savior of the environment

Table 2.3 List of some fungi displaying heavy metal remediation capacities. Fungal species

Property

References

Gloeophyllum sepiarium Sphaerotilus natans Candida parapsilosis Aspergillus niger P.flabellatus P.ostreatus P. pulmonarius

Cr resistance Cr resistance Hg resistance Ni resistance Cd resistance Hg and Cd resistance Pb resistance

Achal et al. (2011) Ashokkumar et al. (2017) Muneer et al. (2013) Ta¸stan et al. (2010) Kapahi and Sachdeva (2017) Kapahi and Sachdeva (2017) Kapahi and Sachdeva (2017)

The results revealed the presence of three metal tolerant fungal species. The bioleaching capacities of the fungal colonies were also excellent revealing them, to be significantly efficient bioaccumulators (Khan et al., 2019). Some fungal species discovered to have heavy metal remediation capabilities are listed below (Table 2.3). Mushrooms can also be employed for the decontamination of the environment. They can build up high levels of heavy metals concentrations in their bodies much greater than the permissible levels. This capability and also their low life span make them a good choice as mycoremediants. The Pleorutus species or as it is commonly known oyster mushrooms are normally found to be growing in the wood. It has been found that this species has a high capacity to accumulate heavy metals inside their fruiting bodies with the increase of metal concentration in their substrate. Oyster mushrooms growing near contaminated areas such as traffic highways and smelter factories have been reported to accumulate heavy metals in far greater concentrations than possible. P. ostreatus has been observed to have an affinity toward the accumulation of mercury and cadmium, whereas P. flabellatus has an affinity for only cadmium. This species also can rejuvenate the health of the environment. A considerable decrease in the lead concentration of battery polluted soil was observed after the introduction of P. pulmonarius (Kapahi and Sachdeva, 2017).

3.5 Bioventing and biosparging Bioaugmentation projects typically depend upon water to transport the necessary trace minerals, phosphates, electron acceptors, and nitrogen which can enhance the microbial activity of the soil. In situ bioremediation techniques like these focus typically upon the saturated region of the soil only. Little or no attention is given to the capillary region and the deeper regions where the majority of the contamination might occur. Bioremediation of this region with the conventional techniques has proven to be difficult as the equipment cannot timely deliver the oxygen which cannot degrade the organics. A technique that increased the mass transfer of oxygen would thus be more effective in bioremediating the environment. Bioventing was thus introduced. Bioventing is a combined technique that involves soil venting

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and biodegradation. Soil venting is the removal of the volatile components from the soil, and the next step involves the biodegradation of the component using the oxygen from the vented air. A bioventing system consists of a blower and a sequence of induction systems that allow the air to enter into the soil and venting wells (Lee and Swindoll, 1993). Biosparging is another process whereby pressurized air is injected into the soil below to increase the oxygen saturation levels. This increases the rate of degradation of the contaminants and the activity of the microorganisms.

3.6 Cyanoremediation The release of toxic effluents in water bodies has resulted in severe heavy metal contamination. Treating freshwater bodies as industrial sinks has also caused a severe deficiency in drinking water quality as well as quantity. Conventional treatment methods not only require a large amount of space but also the cost of the process is very high. For this reason, cyanobacteria were chosen for the treatment of freshwater which was known to harbor high levels of heavy metal concentration. Normally, cyanobacteria strains such as Anabaena, Nostoc, Phormidium, etc. act as bioremediants for nitrates and phosphates. Some have even been known to be used for sewage and effluent treatment, but its use for the treatment of complex pollutants is very rare. The siderophores produced by cyanobacteria may be responsible for the adsorption of metal ions. After the metal has accumulated, then the algal biomass can be either incinerated or removed (Gothalwal and Chillara, 2012). Cyanoremediation helps in bioremediation by a variety of mechanisms such as bioaccumulation and biosorption. Cyanobacteria cells have developed physicochemical methods top respond to heavy metals such as cadmium and lead. Species such as Spiruliina platensis was seen to contain high levels of mercury and lead when they were grown under contaminated conditions. Both Aphanothece flocculosa and Spirulina platensis were seen to act as excellent biosorbents for mercuric ion too. This implied that the cells were taking in metal ions by biosorption as well as by other mechanisms. Metallic mercury is relatively more nontoxic and less soluble than its ionic form. These cyanobacterial cells were seen to regenerate metallic mercury back again from its ionic form. Further investigations also concluded that various binding mechanisms by the carboxyl groups aid the attachment of the metal ions. Intracellular phosphate groups and extracellular polysaccharide present in the live algal biomass also serves in chelating and binding the metal ions. A species of algae, Synechocystis was seen to develop a thick calyx when exposed to higher levels of copper. Synchococcus was found to possess a special ATPase in the thylakoid membrane which aided in transporting copper. This and several other reports have verified that cyanobacteria possess heavy metal remediation capabilities. Cyanobacteria were also employed in effluent treatment. The wastewater from tanneries was seen to contain high levels of Cr (IV) and Cr(VI). Recent researches have employed Nostoc in the treatment of tannery wastes (Gothalwal and Chillara, 2012).

3. Bioremediation: the savior of the environment

Taking into consideration the bioaccumulation properties of Nostoc muscorum and Synechococcus for mercury, lead, and cadmium an experiment was carried out. The test organisms Nostoc muscorum and Synechococcus were obtained and were grown in a BG-11 medium with a nitrogen source. These cultures were subjected to constant agitation and maintained at a pH of 7.5 for 10 days. The cultures were then introduced to mediums containing high concentrations of heavy metals salts. Then they were incubated over a while. Then they were subjected to pigment analysis and to test the heavy metal content present within them. It was seen that mercury followed by cadmium and then lead produced the highest decrease in the percentage of Chlorophyll A for Nostoc muscorum. It was also observed that these two species contained detectable leaves of mercury and lead within them with cadmium showing the highest concentration factor. This confirmed that cyanobacteria Nostoc muscorum and Synechococcus are potential bio accumulators and can be used for detoxifying heavy metals (Rahman et al., 2011).

3.7 Biostimulation Biostimulation is a novel remediation technique that involves the optimization of environmental conditions such as nutrients, pH, and temperature to stimulate the activity of the bacteria present and increase their degradation activity. It also helps in the survival of the indigenous microorganisms by supplementing them with additional nutrients. This can be done by the addition of various limiting nutrients and electron acceptors such as nitrogen, phosphorous oxygen, and carbon, etc. (Adams et al., 2015). The uncontrolled use of Cr (VI) in industries has resulted in the generation of a large amount of waste, which has resulted in the pollution of soil and many aquifers. It has been perceived that microbial degradation of hexavalent chromium is possible and that the activity of these microbes can be promoted by the use of electron donors like acetate, or lactate. A study was carried out to test the efficiency of these microbes when they are stimulated by external agents. Soil samples were collected about 30e40 cm in depth from the outer layer. Then the soil was treated adequately for chromate quantification. About 5 gm of the sample soil was taken and to it 25 mL of NaOH was and sodium carbonate was added at appropriate concentrations. Then it was heated at 100 C for about 1 h. The pH was determined by dissolving the soil in distilled water and measuring it after allowing it to stand for some time. The biostimulation assay was carried thrice at a time. About 15 gm of the soil sample was taken in a sterile glass bottle and to it about twice the amount of distilled water was added. Then nitrogen was injected inside it and it was incubated at room temperature for 3 days. Then about 600 mL of 2M sodium acetate solution was added to the bottles except for the controls. Then they were incubated at 30 C. Simultaneously soil DNA extraction was performed and the PCR products which were obtained were cloned into a suitable vector. Soil enrichment of the assays was done by further addition of cysteine and resazurin and yeast extract. These were then incubated at 30 C. Serial dilution was performed and then plating was done. Pure cultures that were

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obtained were then analyzed accordingly. The experiment was conducted under three conditions simultaneously. In the biostimulated soil, it was seen that almost all of the Cr(VI) was utilized and only 18% of the acetate was consumed. There was no significant change in pH. Thus depicting that biostimulation has a significant impact and can be implemented as a technique for bioremediation (Lara et al., 2017). Biostimulation is advantageous as it does not require the addition of new microorganisms to be added. It requires the indigenous microorganisms only which are well suited to that environment. The main challenge lies however in supplying the necessary additives. Impermeable soil layers possess as a barrier to the equal distribution of nutrients, and also nutrients might support the growth of other species which might not have remediation capacities but instead compete with our native species (Lara et al., 2017).

3.8 Bioleaching Bioleaching is another bioremediation process that involves the use of microorganisms to remove or extract toxic heavy metals from the soil. The presence of heavy metals in the soil in high concentrations can lead to serious health complications. Therefore the removal of them from the soil is very important. Washing of the soil with acidic aqueous solutions have been implemented on a pilot scale; however, they are not very cost-effective. Therefore bioleaching was proposed as a suitable replacement. Previously reports have been made about the use of T. ferrooxidans to remove toxic metals from sewage sludge. Several metabolic pathways were also studied which revealed that Thiobacillus thiooxidans can also be used for the recovery of sulfur, and the combined action of both could be used for the remediation of metal sulfides (Zagury et al., 1994). A study was thus carried out to understand more about the nature of these microorganisms and also to recognize the potential of bacterial bioleaching to solubilize heavy metals from the soil. Soil samples were obtained from different locations. The soil was taken from at least 20e25 cm in depth from the top layer and stored at 4 C. After that, it was dried at room temperature for 12 h, and then it was subjected to analysis. Then, about 2.25 g of soil sample was taken and dissolved in 150 mL of deionized water in a 500 mL Erlenmeyer flask. A fixed concentration of ferrous sulfate was also added and the pH was stabilized after that. Then to acclimatize the bacilli the set up was incubated in a gyrating incubator. The oxidation-reduction potential (ORP) and pH were continuously monitored over 72 h until there was an increase in the ORP along with the acidity. The presence of the thiobacilli was confirmed by a simple test and then the metal bioleaching bioassay was performed (Zagury et al., 1994). The results revealed that the indigenous microorganisms could be easily adapted by supplementing the soil with adequate nutrients. The bacteria once successfully acclimatized then could perform the bioleaching activities, and the pH fluctuation was not a hindrance to the survival of the bacteria (Zagury et al., 1994).

4. Factors affecting bioremediation

4. Factors affecting bioremediation Microorganisms can act as excellent bioremediants; however, the efficiency of this process is dependent upon many factors. The optimization of bioremediation is a complex process that is interdependent upon several different systems (Abatenh et al., 2017) (Table 2.4).

4.1 Availability of nutrients The presence of nutrients adequately balances the microbial growth, its reproduction, and also the degradation rate. For its survival microbes need an adequate quantity of carbon, nitrogen, and phosphorous. These nutrients help in maintaining the metabolic activity of the microbes (Abatenh et al., 2017).

4.2 Temperature Temperature is one of the most important physical factors that affect the metabolic activity of a microbial cell. Low temperatures can block the transport channels, essentially causing the cell to go into a stage of stasis, thus stopping the cell activities. Similarly with increasing temperatures the metabolism also increases and reaches the peak value at an optimum temperature after which on increasing the temperature the metabolic activity reduces and gradually stops (Abatenh et al., 2017). With increasing temperatures, the solubility of heavy metals also increases thus increasing the bioavailability of the metals (Igiri et al., 2018).

4.3 pH Heavy metals tend to be affected by acidic pH. They tend to form free ions under acidic conditions which saturate the metal-binding sites. When hydrogen ion concentrations are higher it reduces the binding of the adsorbent and the metal ions which increases the toxicity (Igiri et al., 2018). Metabolic activities of cells are affected highly even by slight fluctuations in pH (Abatenh et al., 2017). Table 2.4 Some factors influencing heavy metal remediation. Factors

Activities

Microbial

• • • • • • • • •

Substrate Environment

Sustaining able microbial populations Production of toxic metabolic products Mutations Chemical; the structure of contaminants Presence of contaminants Inhibitory conditions Lack of nutrients Temperature pH

References Abatenh et al. (2017); Boopathy (2000) Boopathy (2000); Igiri et al. (2018) Abatenh et al. (2017); Igiri et al. (2018)

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5. Conclusion Heavy metals are very important to us in many respects. They are used for the manufacturing of many essential products and also serve as principal elements in biological systems. However, excessive exposure to heavy metals in large quantities can lead to cytotoxic effects which may prove to be fatal (Duruibe et al., 2007). Heavy metal pollution has been a grave issue and has resulted in significant damage to the environment. This is a huge problem for countries going through rapid industrialization. Bioremediation is proving to be a cost-effective and yet efficient technique to tackle this problem. Other physical and chemical techniques exist and are also being used. However, the financial strain becomes too much for many nations, especially third world countries. The idea of bioremediation was there previously but the applications are new and proving to be very useful. Various ex-situ and in-situ techniques are being developed to treat environmental contaminants. Both microorganisms and plants have been seen to possess natural bioremediation capabilities. This helps them to survive under high metal concentrations. Bioremediation essentially converts toxic wastes into relatively harmless products. For example, heavy metals are hazardous in their ionic states; bioremediation converts them to more stable nonionic states. It is also a completely natural process and requires much less energy. However, there are also some disadvantages, and the process is time-consuming. The process of biodegradation by microbes is also very specific and is influenced by several external factors (Kulshreshtha et al., 2014). Prospects of bioremediation lie with transgenic microorganisms. However, it should be strictly monitored so that no lethal side effects occur to the environment and there are no fatalities. Expedite research are required to understand more about them and also to increase their adaptability in various environmental conditions. A metagenomic analysis along with metabolic analysis is also required to understand more about the nature of the bacterial colonies that inhabit the polluted sites (Ojuederie and Babalola, 2017).

References Achal, V., Kumari, D., Pan, X., 2011. Bioremediation of chromium contaminated soil by a brown-rot fungus, Gloeophyllum sepiarium. Res. J. Microbiol. 6 (2), 166. Adams, G.O., et al., 2015. Bioremediation, biostimulation and bioaugmention: a review. Int. J. Environ. Bioremediat. Biodegrad. 3 (1), 28e39. Akhtar, N., Iqbal, J., Iqbal, M., 2004. Removal and recovery of nickel (II) from aqueous solution by loofa sponge-immobilized biomass of Chlorell a sorokiniana: characterization studies. J. Hazard Mater. 108 (1e2), 85e94. Arora, N.K., 2018. Bioremediation: A Green Approach for Restoration of Polluted Ecosystems. Springer. Ashokkumar, P., Loashini, V.M., Bhavya, V., 2017. Effect of pH, Temperature and biomass on biosorption of heavy metals by Sphaerotilus natans. IJMM 6 (1), 32e38.

References

Abatenh, E., et al., 2017. The role of microorganisms in bioremediation-A review. J. Environ. Biol. 2 (1), 030e046. Bhattacharya, A., Gupta, A., 2013. Evaluation of Acinetobacter sp. B9 for Cr (VI) resistance and detoxification with potential application in bioremediation of heavy-metals-rich industrial wastewater. Environ. Sci. Pollut. Res. 20 (9), 6628e6637. Boopathy, R., 2000. Factors limiting bioremediation technologies. Bioresour. Technol. 74 (1), 63e67. Chen, H., Pan, S.-s., 2005. Bioremediation potential of spirulina: toxicity and biosorption studies of lead. J. Zhejiang Univ. Sci. B 6 (3), 171. Congeevaram, S., et al., 2007. Biosorption of chromium and nickel by heavy metal resistant fungal and bacterial isolates. J. Hazard Mater. 146 (1e2), 270e277. Duruibe, J.O., Ogwuegbu, M., Egwurugwu, J., 2007. Heavy metal pollution and human biotoxic effects. Int. J. Phys. Sci. 2 (5), 112e118. Emenike, C.U., et al., 2017. Optimal removal of heavy metals from leachate contaminated soil using bioaugmentation process. Clean 45 (2), 1500802. Gavrilescu, M., 2004. Removal of heavy metals from the environment by biosorption. Eng. Life Sci. 4 (3), 219e232. Gothalwal, R., Chillara, S., 2012. Cyanoremediation: a green clean technology. In: Microorganisms in Environmental Management. Springer, pp. 767e786. Igiri, B.E., et al., 2018. Toxicity and bioremediation of heavy metals contaminated ecosystem from tannery wastewater: a review. J. Toxicol. 2018. Kapahi, M., Sachdeva, S., 2017. Mycoremediation potential of Pleurotus species for heavy metals: a review. Bioresour. Bioprocess 4 (1), 32. Khan, I., et al., 2019. Mycoremediation of heavy metal (Cd and Cr)epolluted soil through indigenous metallotolerant fungal isolates. Environ. Monit. Assess. 191 (9), 585. Kulshreshtha, A., et al., 2014. A review on bioremediation of heavy metals in contaminated water. Iosr-Jestft 8 (7), 44e50. Kumar, R., et al., 2011. Sorption of heavy metals from electroplating effluent using immobilized biomass Trichoderma viride in a continuous packed-bed col umn. Int. Biodeter. Biodegr. 65 (8), 1133e1139. Lara, P., Morett, E., Jua´rez, K., 2017. Acetate biostimulation as an effective treatment for cleaning up alkaline soil highly contaminated with Cr (VI). Environ. Sci. Pollut. Res. 24 (33), 25513e25521. Lee, M.D., Swindoll, C.M., 1993. Bioventing for in situ remediation. Hydrolog. Sci. J. 38 (4), 273e282. Majumder, S., et al., 2015. A comprehensive study on the behavior of a novel bacterial strain Acinetobacter guillouiae for bioremediation of divalent copper. Bioproc. Biosyst. Eng. 38 (9), 1749e1760. Mohammed, A.S., Kapri, A., Goel, R., 2011. Heavy metal pollution: source, impact, and remedies. In: Biomanagement of Metal-Contaminated Soils. Springer, pp. 1e28. Muneer, B., et al., 2013. Tolerance and biosorption of mercury by microbial consortia: potential use in bioremediation of wastewater. Pakistan J. Zool. 45 (1), 247e254. Ojuederie, O.B., Babalola, O.O., 2017. Microbial and plant-assisted bioremediation of heavy metal polluted environments: a review. Int. J. Environ. Res. Publ. Health 14 (12), 1504. Pajuelo, E., et al., 2011. Legumeerhizobium symbioses as a tool for bioremediation of heavy metal polluted soils. In: Biomanagement of Metal-Contaminated Soils. Springer, pp. 95e123.

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Pan, R., et al., 2010. Biosorption of Cd, Cu, Pb, and Zn from aqueous solutions by the fruiting bodies of jelly fungi (Tremella fuciformis and Auricularia polytricha). Appl. Microbiol. 88 (4), 997e1005. Pepper, I.L., et al., 2002. The role of cell bioaugmentation and gene bioaugmentation in the remediation of co-contaminated soils. Environ. Health Perspect. 110 (Suppl. 6), 943e946. Rahman, M.A., et al., 2011. Evaluation and sensitivity of cyanobacteria, Nostoc muscorum and Synechococcus PCC 7942 for heavy metals stressea step toward biosensor. Toxicol. Environ. Chem. 93 (10), 1982e1990. Rahman, Z., Singh, V.P., 2019. The relative impact of toxic heavy metals (THMs)(arsenic (As), cadmium (Cd), chromium (Cr)(VI), mercury (Hg), and lead (Pb)) on the total environment: an overview. Environ. Monit. Assess. 191 (7), 419. Rajkumar, M., et al., 2012. Perspectives of plant-associated microbes in heavy metal phytoremediation. Biotechnol. Adv. 30 (6), 1562e1574. Ray, S.A., Ray, M.K., 2009. Bioremediation of heavy metal toxicity-with special reference to chromium. Al Ameen J. Med. Sci. 2 (2), 57e63. Rehman, K., et al., 2018. Prevalence of exposure of heavy metals and their impact on health consequences. J. Cell. Biochem. 119 (1), 157e184. Salehizadeh, H., Shojaosadati, S., 2003. Removal of metal ions from aqueous solution by polysaccharide produced from Bacillus firmus. Water Res. 37 (17), 4231e4235. Ta¸stan, B.E., Ertugrul, S., Do¨nmez, G., 2010. Effective bioremoval of reactive dye and heavy metals by Aspergillus versicolor. Bioresour. Technol. 101 (3), 870e876. Tchounwou, P.B., et al., 2012. Heavy metal toxicity and the environment. In: Molecular, Clinical and Environmental Toxicology. Springer, pp. 133e164. Zagury, G.J., Narasiah, K.S., Tyagi, R.D., 1994. Adaptation of indigenous iron-oxidizing bacteria for bioleaching of heavy metals in contaminated soils. Environ. Technol. 15 (6), 517e530. Zouboulis, A., Loukidou, M., Matis, K., 2004. Biosorption of toxic metals from aqueous solutions by bacteria strains isolated from metal-polluted soils. Process Biochem. 39 (8), 909e916.

CHAPTER

Microbial degradation of pesticides: microbial potential for degradation of pesticides

3

Sangeeta Kumari, Deepak Kumar, S.M. Paul Khurana Amity Institute of Biotechnology, Amity University Haryana, Gurugram, Haryana, India

1. Introduction: pesticides effect on environment health During the last two decades, the increased use of pesticides globally has coincided with changing farming practices, especially the intensification of agriculture. In the process, the rise in the use of pesticides in agriculture and other nonagricultural sectors has led to an increased presence of residues of pesticides in many environmental matrices (Fig. 1.3). Pesticide pollution of water worldwide is the major issue of concern in all sectors of society, be it local, regional, and national scales (Huber et al., 2000; Cerejeira et al., 2003; Zhang and Zhang, 2011). The chlorinated organic pesticides such as Aldrin, heptachlor, Endosulfan, and dichloro-diphenyl-trichloroethane (DDT) are among the several compounds of great concern because they have the tendency to bioaccumulate in living cells and cause disease complications in humans (Jayaraj et al., 2016). They are also known to affect soil flora and fauna (Bhat and Padmaja, 2014). Incessant use of synthetic pesticides has also contributed to the disappearance of beneficial organisms present in the soil. Pesticides, in addition to polluting the ecosystem (including water), its residues find entry into the food chain and impact useful organism such as earthworms, bees, and spiders directly or indirectly (Singh et al., 2014). The organophosphate (OP) group contains a number of broad-spectrum insecticides that are widely used on various crops including fruits and vegetables as well as ornamentals. Insecticides belonging to this group has the potential to cause adverse effects to the central nervous system of human beings at subtle doses and have detrimental effects on aquatic life, bees and birds as well. The United States Department of Agriculture through its Pesticide Data Program (PDP) indicated that in 2005, about 73% of fresh fruits and vegetables and about 61% of processed fruits and vegetables were detected with pesticide residues (Yang et al., 2008). Our daily intake of food contains traces of multiple prohibited pesticides such as DDT, benzene hexachloride (BHC), Aldrin, dieldrin, and lindane, among others, which find their way through food into the human body resulting into health disorders. The green revolution that occurred in India has left the environment with a toxic load of Development in Wastewater Treatment Research and Processes. https://doi.org/10.1016/B978-0-323-85657-7.00005-5 Copyright © 2022 Elsevier Inc. All rights reserved.

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pollutants following overuse of chemical fertilizers, which have somehow found their route through the food chain into human beings (Rangarajan, 2001). The high toxicity, stability, and minimal solubility of active substances is the main cause of the negative impact of insecticides, and organochlorinated pesticides (OC) are topping the list in this regard (Odukkathil and Vasudevan, 2013; Rani and Dhania, 2014). Organochlorines have been implicated in neurotoxic, developmental, immunological, genotoxic, and tumorigenic effects in humans and animals (Jayaraj et al., 2016). The wide use of high yielding crops that characterized the green revolution paralleled the increased use of pesticides which eventually led to health complications such as farmers and farm work poisoning, neurological and skin disorders, miscarriages, fetal abnormalities, and reduction of sperm count among applicators (Bag, 2000). The USEPA defines pesticides as substances that are prepared with the intention of managing pests (mites, insects, nematodes, weeds, rats, etc.), and may include herbicides, insecticides, fungicides, and other compounds utilized for pest control (USEPA, 2011). India is using various pesticides for managing pests and in order to boost crop production (Arisekar et al., 2019). The pesticide use in India has been extensive in agriculture and public health sectors totaling to 21288 metric tons (MT) during the 2012e2013 year, 26096 MT during the 2013e2014 year, 20002 MT during the 2014e2015 year, 20622 MT during the 2015e2016 year and 28583 MT during the 2016e2017 year (reported by Ministry of Agriculture and Farmers Welfare). The insecticide DDT, for instance, with concentrations exceeding 2000 MT was used in India to control mosquitos in 2013 (Van Den Berg et al., 2017). Another insecticide, Endosulfan, traded under various names has also seen widespread use (Leena and Govindan, 2012). Though several insecticides like lindane, Endosulfan, DDT, Aldrin, Heptachlor, etc. are discontinued in other countries, the majority are still being used in India. The increased use of pesticides globally over the last two decades has coincided with changing farming practices, particularly, agricultural intensification. The hype in pesticide use in agriculture and other nonagricultural sectors has in the process resulted in the increased presence of pesticide residues in many environmental matrices. Pesticide pollution of water worldwide is the major issue of concern in all sectors of society be it local, regional and national scales (Huber et al., 2000; Cerejeira et al., 2003; Zhang and Zhang, 2011). The chlorinated organic pesticides such as Aldrin, heptachlor, Endosulfan, and DDT are among the several compounds of great concern because they have the tendency to bioaccumulate in living cells and cause disease complications in humans (Jayaraj et al., 2016). They are also known to affect soil flora and fauna (Bhat and Padmaja, 2014). Incessant use of synthetic pesticides has also contributed to the disappearance of beneficial organisms present in the soil. Pesticides, in addition to polluting the ecosystem (including water), its residues find entry into the food chain and impact useful organism such as earthworms, bees, and spiders directly or indirectly (Singh et al., 2014).

1. Introduction: pesticides effect on environment health

1.1 Pesticides Throughout the past five decades, pesticides have been an important part of agricultural intensification. Although the benefits of using pesticides are evident in terms of improving agricultural output and growing demands for production and distribution, indiscriminate benefits are also inclined (Goswami and Singh, 2009; Vijgen et al., 2011). Pesticides are substances that are toxic to potential risks to the environment (Golfinopoulos et al., 2003; Srivastava and Shivanandappa, 2010; Pavlı´kova´ et al., 2012).

1.2 Classification of pesticide Pesticides are a general term of various types of chemical substances that include herbicides, fungicides, insecticides and rodenticides; and they are categorized based on their structure (Table 3.1) such as OC, OP, carbamates, and nitrogen-based (Table 3.2).

1.3 Pesticide fate in the environment An understanding of the behavior and migration of chemicals after they have been used is paramount as it aids the pesticide user to ensure that the application is effective as well as environmentally safe. Pesticide movement may be beneficial to the intended organism however, it may also be hazardous. Pesticides can be moved away by runoff from its target, and as a result it gets wasted, control is inefficient, and it has the potential to affect other nontarget organisms (Li et al., 2018). Table 3.1 Pesticide classification. Pesticide

Example

Insecticides Organophosphorus Carbamate Organochlorine Cyclodienes Herbicides Nitrogen-based Organophosphates

Diazinon, Dichlorvos, Dimethoate, Malathion, Parathion Carbaryl, Propoxur, Aldicarb methiocarb DDT, Methoxychlor, Toxaphene, Mirex, Kepone Aldrin, Chlordane, Dieldrin, Endrin, Endosulfan, Heptachlor Chlorophenoxy acids, Hexachlorobenzene (HCB) Picloram, Atrazine, Diquat, paraquat Glyphosate (Roundup)

Fungicides Nitrogen-containing Wood preservatives Botanicals Antimicrobial

Triazines, Dicarboximides, Phthalimide Creosote, Hexachlorobenzene Pyrethrins Chlorine, Quaternary alcohols

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CHAPTER 3 Microbial degradation of pesticides

Table 3.2 Range of toxicity of pesticides. Routes of exposure Oral LD50 Inhalation LC50 Dermal LD50 Eye Effects

Skin Effects Signal Word

Toxicity category I

II

III

IV


50 mg/kg and including 0.2 mg/L Up to and including 200 mg/kg Corrosive corneal opacity not reversible within 7 days

50e500 mg/kg 0.2e2 mg/L

500e5,000 mg/kg 2e20 mg/L

>5,000 mg/kg >20 mg/L

200e2,000 mg/kg

2,000e20,000 mg/kg

>20,000 mg/kg

Corneal opacity Reversible within 7 days; irritation persisting for 7 days Severe irritation at 72 h Warning

No corneal opacity; irritation reversible within 7 days

No irritation

Moderate irritation at 72 h Caution

Mild or slight irritation at 72 h Caution

Corrosive Danger Poison

Adsorption is the process by which a pesticide binds to the soil particles and the degree of persistence vary with the type of pesticide, soil texture, soil moisture, acidity, and content. Soils that are rich in clay or mud tend to be more adsorptive than course, sandy soils, due to the availability of more particulate matter onto which pesticides may bind. Pesticides adsorbed to soil are less volatile and available for absorption by plants or animals and other processes that affect them (Jin et al., 2013; Han et al., 2019). Absorption, the process by which plants, animals, humans, or microbes that take up the chemicals is affected by environmental factors and physicochemical properties of the pesticides and soil (Glinski et al., 2018). The processes of change to gas from the solid or liquid state are called volatilization and volatilized pesticides may result into the movement of a pesticide in its gaseous form from a treated area via air currents. In addition, this process is undetectable, unlike drift of actual spray that can be visualized during application (Hendriks et al., 2019). Runoff refers to the water movement over the soil surface and this moving water can transport pesticides in either water solubilized form of bound to eroding soil. A number of factors such as slope quality of the area, erodibility, moisture and texture of soil and the intensity of rainfall affect pesticide runoff. Additionally, the physicchemical properties of a pesticide such as an uptake by plants may also affect runoff (Hendriks et al., 2019). Pesticides can also be transported in water through leaching and it may occur as water moves downslope through the slope. Pesticide leaching can be affected by

1. Introduction: pesticides effect on environment health

several factors and these include the pesticide solubility in water. A pesticide that is readily soluble can leach rapidly as the water percolates through the soil. The permeability and amount of persistence of pesticide in the soil are also influenced by the soil texture and structure. Hendriks et al. (2019) indicated that adsorption probably is the most significant factor that influences the leaching of pesticides and soil adsorbed pesticides are less likely to leach out of the environment. Tsydenova et al. (2015), Vela et al. (2019) indicated that photolysis may be a critical degradation pathway under aqueous conditions as well as in the gas phase and this process can be rapid and the products vary ranging from the oxidized P¼S bond to the isomerization of the starting organophosphate pesticide. With regards to ground water, whether the pesticide reaches ground water or is degraded before reaching it depends on the pesticide fate and other environmental conditions and processes. In view of the aforementioned issues, the water table depth and sinkholes become paramount. If the water table is near the surface, there could be few chances of pesticide binding and degradation to occur as there are more chances of volatilization or taken up by the plants as well as photolysis and breakdown by microbes and reacting with other chemicals. Hence, leaching is depended on both pesticide and soil properties. Management practices as well as weather also may affect leaching of a pesticide. There can be leaching or runoff of a pesticide beyond the treatment area due to too much rain or irrigation water. As such less volatilized or absorbed pesticides have the potential to move through the soil and contaminate groundwater (Fig. 3.1). Arisekar et al. (2019) investigated the OC and pyrethroids pesticide in surface water of Thamirabarani River in Southern India and found their concentration above the permissible limit set by Bowen and Ebi (2017). Khuman and Chakraborty (2019) reported pesticide residues such as HCH, DDT, Endosulfan in the Hooghly River (perennial transboundary river Ganga) in India. Khuman et al. (2018) evaluated 16 compounds from the riverline sediments and surface waters of Brahmaputra and Hooghly Rivers, where average concentration was 4.8 mgL1.

FIGURE 3.1 Fate of pesticide residues in the environment.

45

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CHAPTER 3 Microbial degradation of pesticides

The organochlorine and organophosphate pesticide remain in the Vasai Creek water near Mumbai were assessed by Singare (2016), and he reported that the mean concentration of a- and b-Endosulfan (137.75 ng/L) exceeded the chronic criteria level of a- and b-Endosulfan (6.5 ng/L) for freshwater aquatic organisms set by the USEPA. He further found that the levels of Aldrin (75.31 ng/L), dieldrin (71.19 ng/L), and Endrin (76.60 ng/L) had exceeded the set limits of 20% of their dry cell weight (DCW) as lipids. It was recently discovered that few oleaginous microbes could synthesize lipid from lignin-based aromatics. For example, Rhodococcus is considered a promising lignin-degrading species because of its rapid growth and tolerance different aromatics, broad substrate specificity, and strong potential for lipid production. Rhodococcus bacteria can utilize various lignin derivatives. These derivatives undergo ring cleavage and are converted to an essential precursor for lipid biosynthesis, acetyl-CoA (Xu et al., 2019). Kosa and Ragauskas, (2012) explored two strains of R. opacus DSM 1069 and R. opacus PD 630 to analyze their capabilities to use lignin model compounds. It was concluded that the bacteria were capable of growing on 4-hydroxybenzoic acid (HBA) and vanillic acid (at the concentration of 0.5% (w/v)) as sole carbon sources. The accumulation of triacylglycerols (>20% of their DCW) was also observed under a nitrogen-limiting condition (C/N ratio ¼ 10:1). Different isolated lignins have also been used as carbon sources for the fermentation of Rhodococcus species because of their ability to depolymerize

209

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CHAPTER 9 Microbial degradation of lignin

Table 9.2 Lignin valorization and production of high-value compounds. Bioproduct Microbial lipids

Microorganism

Substrate

Remark

References

Rhodococcus opacus DSM 1069

4- HBA and vanillic acid

Accumulated fatty acids reached 16.8% of DCW with 4-HBA, 8.7% with vanillic acid within 24 h Accumulated fatty acids reached 20.3% with 4-HBA, 14.6% with vanillic acid within 48 h. Max. lipid accumulation with O2 pretreatment was 0.067 g/L and 14.21% of DCW after 36 h. Higher lignin degradation and lipid accumulation (0.39 g lipid/g DCW) by cofermentation Synergistic effect of laccase increased lipid accumulation by 17-fold to 0.15 g/ L Trace amount (44.3% and PO4 >95% 99%, 88.5% and 90.17%

Ajayan et al. (2015)

Scenedesmus sp.

Cr (VI) > 98%, Nitrates>90%, phosphates >99%, and BOD >88%

Belle´n et al. (2016)

Copper, zinc, iron, chromium, nickel

Chlorella vulgaris

Copper-71%, Zinc-50%, Iron-45%, Chromium-40%, Nickel-20%

S. S. P. and R. P. (2018)

BOD & COD, total nitrogen, total phosphorous, Cr (VI), TDS

Consortium of Chlorella sp. and Phormidium sp.

BOD & COD >90%; 91%, 88%, upto 95%, upto 60%

Das et al. (2018)

Aravindhan et al. (2009) Hanumantha Rao et al. (2011)

Begum et al. (2015)

CHAPTER 14 Microbial remediation of tannery wastewater

Wastewater source

318

Table 14.4 Remediation of tannery wastewater using algal cultures and their removal efficiencies against target pollutants.

Tannery wastewater, VIT Vellore, Tamilndau, India Synthetic wastewater Tannery wastewaterVellore, Tamilnadu, India Tannery wastewaterVellore, Tamilnadu, India

NH3eN, PO4eP, COD

Chlorella vulgaris, Pseudochlorella pringsheimii

NH3eN>65%, 100% for PO4eP, COD,>63%, Cr>80%

Saranya and Shanthakumar (2019)

Cr (VI)

Dunaliella salina

66.4%

Heavy metals (chromium, nickel, lead, copper, cadmium, zinc, and cobalt) and BOD, COD

Neochloris aquatica

Cr- 98.5%, Pb- 97.8%, Ni-98.9%, Cd94.5%, Zn-95.9%, Cu-98%, Co-99.5% and BOD & COD > 98% both

Vidyalaxmi et al. (2019) Tamil Selvan et al. (2020)

COD, color, odor, inorganic carbon, NHþ 4 -N, PO4eP, chromium and TDS

Nannochloropsis oculata þ ozone treatment

84%, 60%, 100%, 90%, 82%, 100%, 97%, 10%

Saranya and Shanthakumar (2020)

5. Microbial remediation 319

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CHAPTER 14 Microbial remediation of tannery wastewater

(Sharma and Malaviya, 2014). Fungal strains isolated from a tannery effluent comprising Aspergillus niger, A. terreus, Phanerochaete chrysosporium and Paecilomyces varioti successfully changed pH from acidic to neutral, and reduction of BOD, COD, TSS, and TDS by over 50%e80% in a study (Deepa et al., 2011). The study suggested the application of polyculture instead of monoculture for effluent treatment. COD and TOC were reduced by about 91% and 93%, respectively by Botryosphaeria rhodina in a laboratory scale experiment. This can be scaled up for treating tannery organic content (Hasegawa et al., 2011). A study conducted to examine fungal capacity for heavy metal sorption from tannery effluents reported Cephalosporium curtipe, Aspergillus candids, Aspergillus flavipes have removed lead (Pb) from tannery by 36%, 54% and 48% respectively (Eman and Eman, 2013). These fungal strains were capable of removing Cu, Fe, Mn, Cr, and Sr also. Hexavalent chromium was reduced up to 96.3% by Aspergillus niger (Sivakumar, 2016). Penicillium sp. was found to have potential for nickel (Ni) removal with 50% efficiency (Khan et al., 2017). Application of Aspergillus niger for Color, COD, TS, TDS, TSS, chlorides, sulfides and chromium removal showed potential results (Sharma and Malaviya, 2013). It reported 81.58% COD and 62.21% color removal from tannery effluent using A. niger. In a different study using Aspergillus niger for tannery effluent treatment resulted into 71.9%, 72.1%, 69.0%, 65.0%, 68.1%, 66.8%, 65.7% and 57.8% removal of color, COD, TS, TDS, TSS, chlorides, sulfides and chromium respectively (Bisht and Harsh, 2014). Fungal strains Cladosporium uredinicola and Bipolaris maydis effectively removed hexavalent chromium, sodium, turbidity, and total solids from the tannery effluents (Joseph et al., 2019).

6. Challenges and limitations to biological wastewater treatment methods employed in tannery industries Tannery wastewater contains a huge amount of organic matter, salts and heavy metals particularly the hexavalent chromium. Also, the amount of total dissolved solids is high in tanneries effluents owing to consumption of a diverse range of chemicals (Durai et al., 2011). Microorganisms require suitable environmental growth conditions. Any fluctuations in physicochemical parameters of surrounding environment affect the microbial metabolism adversely. They require optimum temperature, pH, air availability, salinity, ionic concentration, conductivity, nutrients and light (in case of algae) for their proper growth and development. Heavy metals affect the respiration and metabolism of microorganisms and hence alter their community structure. Presence of heavy metals in excess can cause cell membrane disruption, inhibition of enzymatic activities, DNA damage, and thus, inhibit growth of microbial cells. Chromium particularly is responsible for reduced oxygen uptake, elongates lag phase, and thus inhibition of cellular growth (Kumar and Bharadvaja, 2020). So high concentration of chromium in tannery effluents limit the application

7. Recent advancements

of microbial remediation for the same and hence require manipulation in microbial culture either genetically or conventionally or any other additional treatment with physicochemical method prior to microbial treatment. High salt-laden tannery effluents prevent the microbial growth (Sivaprakasam et al., 2008). Additionally, fluctuations in ionic concentration of wastewater due to oxidative-reductive processes and change in salt concentration adversely affect the microbial community and thus their treatment efficiency (Durai et al., 2011). Thus, normalization to constant salt concentration is essential prior to tannery effluents are subjected to microbial treatment. So, high salt-tolerating microbial cultures are required to treat tannery effluents. Microbial degradation specific to some selective pollutants may be affected by other microbial populations. The presence of microbes other than those required may decrease the efficiency of the processes. The availability and adaptivity of one microorganism may not apply in places other than its native origin. So, their adaptation to the new environment is crucial for their application in tannery effluents. Also, maintenance and transfer of microbial culture across the globe is not a normal and easy task. It also limits its employment for tannery wastewater treatment (Kumar and Bharadvaja, 2020).

7. Recent advancements 7.1 Metagenomic approach for bioprospecting potential microbes and enzymes for tannery wastewater treatment Microbial remediation of environmental pollutants is one of the most practiced, green and cost-effective method of treatment. Numerous microbes have been isolated and identified to have potential for degradation and deterioration of various environmental pollutants. Identification and characterization of each microbe present in an environmental sample is a tedious job. Only culturable microbes have been isolated, identified, assessed, and utilized for pollutant remediation. Some microbes are nonculturable as they only exist and survive in an environmental niche. For these microbes metagenomics is a boon. Ever since its advent, metagenomics has been extensively used in bioprospecting of microbes and derived products of industrial importance. Lately, its role has been investigated for identification of microbial populations having potential for remediation of various pollutants present in industrial wastewater. Metagenomics facilitates information on microbial community and their functional role present in an environmental sample. It helps in widening of our understanding of biodegradation mechanism, degradation pathways, microbes and their genes involved in bioremediation and thus can ultimately help in increasing the microbial remediation efficiency. The role of metagenomics in bioprospecting of microbes, enzymes, degradation genes, and pathways having potential for bioremediation of pollutants present in tannery wastewater has been explored by several researchers. Verma and Sharma (2020) performed nextgeneration sequencing (NGS)-based characterization of microbial diversity and

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functional profiling of solid tannery waste metagenomes and found prominent microbial species comprising Bacillus sp., Clostridium sp., Halanaerobium sp., and Pseudomonas sp. having potential role for tannnery solid waste decomposition (Verma and Sharma, 2020). Chandra et al. (2011) reported major active microbial population for degradation and detoxification of tannery wastewater. Prominent microbial population included Escherichia sp., Stenotrophomonas sp., Bacillus sp., Cronobacter sp., Stenotrophomonas sp., and Burkholderiales bacterium which were able to significantly reduce BOD (92%), COD (88%), total solid (90%), total nitrogen (58%), sulfate (55%), phosphate (70%), and organic pollutants (77%) (Chandra et al., 2011). For nitrification, ammonia-oxidizing bacteria, and nitriteoxidizing bacteria play a central role. Nitrosospira, Nitrosomonas, and Nitrospira were prominent active microbial population responsible for nitrogen depletion in a tannery wastewater (Ma et al., 2018). A prominent denitrifier Brachymonas denitrificans was present in abundance in a tannery wastewater treatment plant. Metagenomic profiling revealed high level abundance and occurrence of denitrification genes (nosZ, narG, napA, norB, and nrfA). Also, the abundance of amino acid degradation enzymes (tryptophan synthase, a-KGDH, and pyridoxal phosphate dependent enzymes) was found (Emmanuel et al., 2019). Apart from bioprospecting microbial diversity, enzymes, and genes, metagenomics is also applied to investigate the abundance, occurrence, and profiling of antibiotic resistance genes present in tannery wastewater treatment plant. Presence of antibiotic genes in wastewater treatment plants show that workers working in tannery industries and wastewater treatment plants are vulnerable to various diseases. Thus, metagenomics can provide information on wastewater quality for public health safety.

7.2 Microbial biosensors for detection and monitoring of contaminants present in tannery wastewater Environmental monitoring for the detection of pollutants and their remediation is becoming increasingly important to human civilization. Wastewater discharge from industrial production houses when disposed without proper treatment cause serious problems for surface waterbodies, aquatic lives, microbial community, and also to the human population (Kumar and Bharadvaja, 2019). Moreover, people working in those industries use harsh chemicals including acids, phenolic compounds, and heavy metals face constant risk of health impairment. Chromium is a major pollutant of the tannery industries, which cause several problems to the human population working therein. So, there arose a need for real-time monitoring of environmental pollutants in terms of their composition as well as concentration at regular interval or throughout the time of operation. Various water pollution monitoring devices have been developed to tackle this issue. For example, an electrochemical sensor was developed for detection of tannic acid present in tannery effluents (Xu et al., 2009). Conventional methods of water pollution monitoring are costly and time-consuming. In recent times, microbial whole-cell based biosensors have been developed for detection of several pollutants present in wastewater or soil

References

(Nistor et al., 2002). These biosensors are used to detect the concentration of target pollutant and their monitoring. An early bacterial whole-cell based biosensor was used to monitor the concentration of benzene sulfonate, nonionic surfactants, and phenolic compounds present in tannery wastewater using Escherichia coli (Farre´ et al., 2001). In a whole-cell microbial biosensor, “an electrical current can be obtained from the bacteria’s electron transport chain and this is achieved by using electron mediators which aid current flow between the bacterial cell and the transducer. The current produced is proportional to the level of metabolic activity of microorganism in observation. Biosensor response to toxic challenge most commonly takes the form of a suppression of metabolic activity related to the concentration of the toxicant” (Farre´ et al., 2001). A rapid method for BOD measurement was developed using immobilized microbial membrane for industrial wastewater (Rastogi et al., 2003). A test strip platform based on a whole-cell microbial biosensor for simultaneous on-site detection of total inorganic mercury pollutants in cosmetics without the need for predigestion was recently reported by (Guo et al., 2020). Similar approach can be used for chromium management in tannery wastewater. Microbial biosensors thus can provide opportunity for real-time detection, monitoring as well as biotransformation of environmental pollutants in less or not at all hazardous form.

8. Solid waste management practices Solid wastes include trimmings of raw leather, salts, hair, lime sludge, and organic waste from vegetable tanning, vegetable tanned trimmings, chrome shavings and trimmings, buffing dusts and pretreatment sludge. There a number of ways these solid wastes get disposed off. Trimmings of raw leather are further utilized into glue manufacturing; residual salts are used in curing and in preservation of raw hides and skins, limes are used in construction activities and for filling low-lying areas, organic wastes get used in firing brick kilns, vegetable/chrome tanned trimmings are used for making leather boards and footwear, buffing dust as fuel for boilers and pretreatment sludge is disposed off in low-lying areas as filling materials. Solid waste management practices among tanneries are almost uniform across the globe.

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CHAPTER

Biological methods for degradation of textile dyes from textile effluent

15

Muhammad Shoaib1, 6, Ambreen Ashar2, Zeeshan Ahmad Bhutta3, Iqra Muzammil4, Moazam Ali4, Ayesha Kanwal5 1

Institute of Microbiology, University of Agriculture, Faisalabad, Punjab, Pakistan; 2Department of Chemistry, Government College Women University, Faisalabad, Punjab, Pakistan; 3The Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush Campus, Midlothian, Scotland, United Kingdom; 4Department of Clinical Medicine and Surgery, University of Agriculture, Faisalabad, Punjab, Pakistan; 5Institute of Biochemistry, Biotechnology and Bioinformatics, The Islamia University of Bahawalpur, Bahawalpur, Punjab, Pakistan; 6Key Laboratory of New Animal Drug Project, Gansu Province, Key Laboratory of Veterinary Pharmaceutical Development, Ministry of Agriculture, Lanzhou Institute of Husbandry and Pharmaceutical Sciences of CAAS, Lanzhou, China

1. Introduction Today, a major problem in the world is water pollution, which is being increased day by day due to improper discharge of industrial wastewater into the environment, high use of chemical fertilizers in the agricultural sector, road and building construction. The population is growing rapidly, which negatively affects the provision of drinking water for all. Industrialization, urbanization, and water pollution are accelerating rapidly. It affects not only human life, but also the ecosystem (Donkadokula et al., 2020). There are many chemical plants that process dyes. Here the textile industry has completed the recovery of large quantities of dye and discharge of wastewater after treatment. The textile industry uses a variety of resources/raw materials such as cotton, wool, and synthetic fibers. The textile industry can also be divided into two categories: dry fabric production and wet fabric production. Solid waste is generated in the production of dry fabrics and liquid waste in the production of wet fabrics. The wet processing industry includes following processing operations such as peeling, cleaning, bleaching, mercerizing, dyeing, printing, and finishing. The textile industry is a major source of industrial wastewater because more water is required in various wet cleaning processes. Many chemicals or metals like acids, dyes, surfactants, alkalis, and hydrogen peroxide are present in the water (Holkar et al., 2016). Synthetic dyes are indispensable for various important industries such as leather, paper and textile industry due to their coloring properties. It is estimated that 700,000 tons of different colors are produced annually, from which about 100,000 Development in Wastewater Treatment Research and Processes. https://doi.org/10.1016/B978-0-323-85657-7.00015-8 Copyright © 2022 Elsevier Inc. All rights reserved.

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are commercially available dyes. These colorants play a significant role in textile industry, most of them are usually discharged into the environment without much attention. It is well known that five major industries are responsible for the release of dyes in environmental waste water. The textile industry (54%) discharges the most wastewater dyes, accounting for over half of the existing wastewater dyes in the global environment. Among textile the dyeing industry (21%), the pulp and paper industry (10%), the leather and paint industry (8%), and the dyeing industry (7%) can generate large volumes of wastewater-containing dyes as a result of various related processes. Among other industries using dyes, the textile industry is reported to be utilizing the most dyestuff in the world, at around 10,000 tons per year. In addition, the industry is known to produce about 100 tons of dye wastewater annually, with only one industry producing the highest wastewater-containing dyes. The widespread use of dyes in various processes in the textile industry leads to the formation of a large amount of wastewater-containing dyes. In addition, the textile industry produces a large amount of wastewater-containing dyes due to the huge demand of water in the textile industry for various processes. Due to the various processes in the textile industry, it is necessary to produce a special mixture of chemicals, dyes, and water. After the process is completed, the remaining mixture (dye wastewater) is released into the environment. For example, 85% of dye spills occur during the dyeing process. This dye effluent is the residue of the entire dye mix created at the start of the dyeing process (Katheresan et al., 2018). The use of such hazardous substances has resulted in water and environmental pollution. Dye effluent, also known as dye wastewater, is rich in many harmful chemicals. Wastewater-containing dye usually discharges directly into nearby rivers, drains, standing ponds, or lakes. Wastewater from the textile, printing and dyeing industries consists of 72 toxic chemicals; out of these 72 chemicals only 30 chemicals can be removed from the wastewater. Dye wastewater can be hazardous to animal and human life due to its natural toxicity. Water areas containing dye runoffs stand out due to their color and are easy to find (Mokif, 2019). The presence of dye waste water in the water source is unacceptable, since animals and people need water for their daily activities (bathing, cooking, drinking, washing, etc.). These water-soluble fiber dyes have adversely affected fragile ecosystems throughout the industry and have caused serious environmental problems. Wastewater from dark fibers usually blocks sunlight and therefore effect the aquatic life. More than 10,000 dyes are used in the textile industry today. This includes azo dyes, the largest and most complex category of dyes on an industrial scale. The release of these synthetic azo dyes into the environment adversely affects all life forms (Bhatia et al., 2017). However, when synthetic colors react with other chemicals to form nondegradable byproducts, they can pose a serious health hazard. The scientists found out that many chemicals like sulfur, bat dyes, nitrates, soaps, chromium compounds, and some heavy metals like lead, nickel, cobalt, and, mercury are very toxic and have

1. Introduction

a drastic effect on marine as well as on human life (Gu¨rses et al., 2016). Some carbon containing organic compounds like chlorinated cleaners, hydrocarbon-based plasticizer, formaldehyde-based dye fixers and nonbiodegradable chemical dyes are carcinogenic. Wastewater from textile printing and dyeing factories is not only toxic, but also enriched with mutagenic, teratogenic, and carcinogenic chemicals (Afroze et al., 2015). For example, the well-known carcinogen benzidine is the main component of most azo dyes and poses a threat to living organisms. A blue dye 291 used for the nucleotide dispersion has been identified to cause nucleotide substitutions; the removal or addition of DNA base pairs cause certain errors in genetic code (Rai et al., 2005). The main category of textile dyes, azo dyes, is directly related to human bladder cancer, spleen sarcoma, and liver cancer is the main cause of chromosomal abnormalities in mammalian cells. Due to its high thermal and photostability, the dye can be stored for a long time in an aqueous medium without processing (Raj et al., 1970). Today, the removal of dye molecules from water sources is not only a serious environmental problem, but also a problem for humans too. Methods for recycling and reusing wastewater from dyes have recently attracted people’s attention, as clean water sources can dry out quickly unless a reliable solution is found. The development of a fixative to permanently remove dye particles from textile wastewater has significant environmental benefits (Peng et al., 2018). There are many methods available for removing dye, but not all methods are successful or impractical due to their limitations. An ideal colorant removal method is to effectively remove large amounts of colorant from wastewater in a short time without secondary contamination. We encourage the use of methods that do not produce more harmful byproducts to remove pollutants from wastewater (Rodrı´guezCouto et al., 2009). Chromium (54%e80%) and zinc (98%) are toxic chemicals removed by the help different ways like physical, chemical and biological. The chemical oxygen demand (COD) is used to remove these toxics up to 98%. Cyclic voltammetry transfers electrons from the cathode to the electrode from suspended mercury droplets using cyclic voltammetry, degrades the azo-binding dye chromogen, and uses an inexpensive adsorbent (e.g., crushed shell powder). Wastewater treatment of fibers for biosorption is achieved using a continuous anaerobic batch reactor with a bleaching efficiency of 94.8%. Compared to a single organism in a three-layer fixed-bed reactor, yeast consortium can effectively decolor the dye wastewater. Over the existing physical and chemical methods, the importance of biological methods is increasing due to use of ecofriendly and cost effective methods such as use of fungi, bacteria, algae, and enzymes biodegradation and decolorization of textile wastewater-containing azo dyes (Katheresan et al., 2018). Researchers are currently developing and implementing several new treatment methods by using biological ways to remove toxic chemicals efficiently. Although, this review paper is a little effort to make a review on the present literature and the methods used for decolorization and degradation of dyes.

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2. Types and characteristics of dyes Dyes are colorants used to color materials (fibers, paper, other dyes, etc.). This is possible because the dyes can adhere to the correct material. Dyes have been used by humans for various purposes for over 1000 years. At that time, dyes were usually produced in small quantities from natural materials (such as insects and plants) and were called natural dyes (Kant, 2012). However, the disadvantage of natural dyes is that they have limited versatility, and their soft tones fade when exposed to sunlight or washing (Solis-Oba et al., 2012). Synthetic dyes were not discovered until recently and mass production began due to the growing demand for dyes. WH Perkins invented many synthetic dyes in 1856 and discovered bright, nonfading shades for a wide variety of uses. The present invention solves the problem of natural retention of the colorant, but raises a new problem in that the industry discharges colorant wastewater into the environment without proper treatment. The mordant is necessary for the natural dyes to blend with the fabric. A mordant is an adhesive used to attach natural colorants to a material. Mordants are highly toxic and dangerous compared to artificial dyes (Kant, 2012). Now a days, synthetic dyes are widely used in different fields for different works such as for printing, plastics, cosmetics, and in textiles. The synthetic dye molecules have a complex and stable structure due to the presence of auxiliary pigments (water-soluble binding compounds) and chromophores (compounds that impart color). Because they are manufactured as complex organic substances, they can resist deterioration due to contact with water, cleaning agents, or other cleaning agents (Al-Alwani et al., 2018). Dyes are mainly classified by the fibers to be printed on and the chemical/physical properties of those dyes. A color group is mainly composed of a group of atoms that give a dye a different color; instead, a color enhancer, called auxochromes, is released by removing or providing electrons (Christie, 2001). eN) ¼ Nd, eNO2, O) ¼ (C6H4) ¼ O (quinone sequence), eC) ¼ O are the chromophore functional groups; these functional groups are eNH3, eCOOH, eOH., SO3H and other functional groups (Srinivasan and Viraraghavan, 2010). The auxiliary dye, sulfonic acid group has been reported to provide high solubility in the dye. Dyes can be classified according to their use and solubility. Acid, basic, direct, medium, and reactive dyes are examples of soluble dyes, and azo, disperse, sulfur, and volatile dyes are examples of insoluble dyes (Sudha et al., 2014). Of all types of dyes, azo dyes are the most productive dyes with a yield of 70% and are the most widely used dyes in the world. The largest group of dyes are azo dyes, with eN) ¼ N- being used as the aromatic color group. There are disazo, trisazo, monazo, polyazo, and tetrakisazo dyes depend on the amount of azo groups present. Anthraquinone is the basic unit of this type of dye. It is pale yellow and can be used as a colorant but cannot be classified as a colorant. Dyes containing anthraquinone units are classified as disperse dyes, medium dyes, and vat dyes. Disperse dyes are commonly used to dye nylon, cellulose acetate, and other hydrophobic fibers (Lavanya et al., 2014).

3. Methods of dye removal

3. Methods of dye removal In the late 1990s, dye removal procedures only included pretreatment procedures such as leveling and settling, as there were no restrictions on dye effluent discharge (Robinson et al., 2001). Improvements have been made by introducing more efficient dye removal methods (e.g., filter beds for dye degradation processes and activation sludge) after setting acceptable standards for dye wastewater discharge. Later, in related industries, a system of wastewater treatment from dyes was introduced, called as the traditional method of removing dyes. Due to the high costs of operation and maintenance, the system was not used in production for some time (Afroze et al., 2015). Much research is currently underway to find the ideal dye removal methods to recover wastewater from dye and make it reusable using this method. The existing methods for removing dyes can be divided into three categories: biological, chemical and physical treatment (Tang et al., 2018). Many methods for removing dyes have been studied over the past three decades, but due to the limitations of most methods, few are currently practiced in the industry. Today, people’s attention is primarily focused on the development of inexpensive wastewater treatment methods for the textile industry to protect aquatic organisms in waters. Therefore, these processes can be physicochemical, biochemical, or can work in combined form, and provide an effective method for cleaning water from the pollutants.

3.1 Physicochemical methods This method is easy to use but it is not always cost effective and environment friendly (De Gisi et al., 2016). Higher energy consumption and lower productivity are required due to the large amount of nonrecyclable byproducts and sludge (Khandare and Govindwar, 2015). These methods are not a one-step process, but a multistep process that requires a long storage period. Chemical methods are commonly used to remove organic contaminants by coagulation and agglomeration (Ukiwe et al., 2014). Bhatia et al. (2017) highlighted the effect of coagulation treatment on insoluble dyes compared to water-soluble dyes. For the precipitation and coagulation, pH is changed by the help of expensive chemicals. A main problem is the limiting use of chemical methods including dehydration, control of pH, increase in residual supernatant levels, settling costs, sludge formation, and disposal. This shows that these processes are not cost effective. Adsorption, ion exchange, oxidation processes, and irradiation are many common physical methods of wastewater treatment and obtaining valuable results (Shah, 2014). Since the adsorbent chitin contains amine nitrogen, it exhibits a high adsorption capacity in relation to acidic dyes. Daaˆssi et al. (2016) showed that the waste contains a large amount of adsorbents that can discolor dyes, and colored organic materials that can impart color to the medium at a low cost. Adegoke and Bello (2015) discovered activated carbon, which can process acidic and basic dyes, and their ability to adsorb. Abu-Saied et al. (2013) provided insight into the

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inability of adsorption methods to handle undissolved dyes and a search for alternative desorption methods. Irradiation methods can treat small amounts of water of different colors, but they require large amounts of dissolved oxygen. However, the ion exchange process shows poor results when working with different dyes and reacts poorly under the presence of additives.

3.2 Biological methods Decomposition of the dye by biological methods, such as biological phenomena (e.g., bioremediation), is an environmentally friendly method that allows the dye to be removed from textile wastewater with minimal cost and optimal run time. In most countries/regions, the typical biological method is a widely used method to remove dyes from wastewater (Al-Alwani et al., 2018). The biological method only removes substances dissolved in the wastewater fibers. Degradation effectiveness is effected by the ratio of material/colorants/microbes, their oxygen concentration and temperature in the system. Depending on the oxygen need, biological processes can be categorized into oxygen requiring, anaerobic, hypoxic, permeable, or their combinations. The aerobic process uses microorganisms to remove dyes from industrial wastewater in the presence of oxygen, while the anaerobic process uses microorganisms to remove dyes from industrial wastewater in the absence of oxygen. In practice, treatments used in combinations such as aerobic and anaerobic give better results. This method uses an anaerobic process to remove COD from the wastewater, followed by an aerobic polishing process to purify the wastewater with low COD (Gurses et al., 2020). When the demand for chemical oxygen in the wastewater is high and exceeds 3 g/L, the anaerobic process can only produce “methane biogas.” It contains organic compounds for example polyvinyl alcohol (PVA) and starch, which have higher degradability (Rongrong et al., 2011). Consequently, anaerobic processing is a biogas-producing method that produces methane with a specific calorific value. Some of the energy generated by this combustion can then be used in the aerobic polishing step. In these biological processes, microorganisms adapt to fibrous dyes and new breeding lines naturally exceed survival requirements, converting many dyes into less harmful forms. In this system, a stable mechanism for the biodegradation of dyes is based on enzymatic processes such as lacasses, lignin peroxidase, NADH-DSIP reductase, tyrosinase, hexane oxidase, and aminopyrine-N-demethylase. In fact, colored water is still visible to the environment, as this treatment alone is not enough to completely remove harmful particles from textile wastewater. Traditional methods can meet the COD of the wastewater, but not the COD of water. Water must be dye free or nontoxic. Therefore, a variety of microorganisms and enzymes have been isolated, and attempts have been made to degrade certain dyes. Its use for efficient separation and decomposition of microbes is an interesting biological aspect of fiber wastewater treatment. Besides this method, other traditional methods for removing biological pigment include adsorption of microbial biomass, decomposition of algae, enzymatic decomposition, and cultivation of fungi and microbes. This method

3. Methods of dye removal

should be used with caution and technical ethics. The use of enzymes to remove pigments has become very popular these days as people believe that the biological depigmentation area is the cheapest and safest depigmentation method. The efficiency of the biodegradation process depends on the adaptability of the selected microorganism and the activity of the enzyme (Solis-Oba et al., 2012). Biological processes of complete decomposition of fibrous wastewater have the following advantages: (a) environmental friendliness, (b) low cost, (c) low sludge formation, (d) harmless metabolites or ensuring full mineralization, and (e) low water usage (increased concentration or low dilution) versus physical/oxidative methods (Hayat et al., 2015). This process concerns living beings, its main disadvantage is the growth rate. System instability often occurs when biological dyes are removed because growth and reaction rates are difficult to predict.

3.2.1 Fungi as biodegradable agent for textile dyes Fungal cultures have the ability to adapt their metabolism to varying environmental circumstances. This ability is essential for their survival. Here, intracellular and extracellular enzymes contribute to metabolic activity. These enzymes have the ability to break down various dyes present in textile wastewater. Depending on these enzymes, different types of fungal cultures, including colorants, are suitable for the decomposition of dyes in wastewater. The different types of enzymes secreted by different types of fungal cultures are laccases, manganese peroxidase, and lignin peroxidase (Chen and Ting, 2015). Various types of fungi have been reported and attempts have been made to purify wastewater from dying plants. The combination of aerobic and anaerobic treatments with a variety of microorganisms has shown promising results with regard to the biodegradation of fiber dyes. Typically, a white-rot fungus culture was used to remove the azo dye, Coriolopsis sp (Chen and Ting, 2015), Penicillium simplicissimum (Chen and Ting, 2015), and Pleurotus eryngii (Hadibarata et al., 2013) decompose with COD removal. However, the decomposition of colorants in fibrous wastewater by white-rot fungi has a long growth period and a nitrogen-limited environment, unreliable enzyme production, and a large reactor size (because it takes a long time for complete decomposition) (e.g., Anastasia). Several researches have been done on the discoloration of dyes based on fungal cultures as an alternative for the present physical and chemical processes (Pla´cido et al., 2016). Phanerochaete chrysosporium can be used as an effective model in paper and pulp industry for treating wastewater which contains polycyclic aromatic hydrocarbons (PAH). Senthilkumar et al. (2014) investigated Phanerocheate chrysosporium, which produces extracellular enzyme for example lignin peroxidase, Mn peroxidase, and laccase initiated discoloration of various pigments. Singh and Singh (2010) investigated another mushroom called Trichoderma harzianum, which was used to treat wastewater from the textile industry. Using a semisolid potato dextrose agar (PDA) medium, the fungal filament destroyed bromophenol and congo red completely in a fixed amount. This study showed that media containing

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bromophenol blue, congo red, acid red, simple green, and Trichoderma harzianum (proliferation in media without dyes) production is controlled by the help of basic blue (Table 15.1). Among these dyes, bromophenol blue showed the greatest inhibitory effect on growth (43%). Its characteristics like broad spectrum, fast growth, and large amount of biomass of mycelium, various fungal cultures are used for bioremediation, which makes them more efficient than bacteria (Anastasi et al., 2013). It was investigated that the strain of Aspergillus, which is MF3, and it optimized the NaCl concentration for efficient degradation of Orange 3R fiber dye with an efficiency of about 96% under ideal conditions on the fifth day. At a NaCl concentration of 1.0%, discoloration of dye was found 56%, with further decrease in concentration as 44% and 42% was observed at NaCl concentrations of 1.5% and 2.0% decreased respectively. The color change observed very clearly on a fifth day, the reactions could be carried out at different concentrations of NaCl. It has greater decolorizing power, functioning in pristine situations, and this strain has attracted the attention of people in the biological treatment of wastewater from dye factories. The marine fungi is used in the bioremediation processes as well as it has the capability to break down the reactive blue-4 dyes which is one of the form of anthraquinone dyes. The degradation process consists of two stages. In the first stage, the refined varnish is partially processed, then the compound (with a lower molecular weight) at the end considered as an enzymatic degradation procedure. As a result, it was confirmed that the total carbon content was 29% and the toxicity was doubled. A subtype of Aspergillus oryzae used for the bioadsorption of azo dyes (Bhatia et al., 2017). Chairin et al. (2013) investigated the color change and removal of bisphenol A and other self-made dyes uses laccase enzyme isolated from Trametes polyzona strain WR710-1. After the laccase treatment, the degree of discoloration of the anthraquinone dye (Reactive Blue 4) was about 61%, and the COD decreased by half. Evaluation of metabolites synthesized throughout the entire process is performed using mass analysis, UPLC, and UV spectroscopy. A combination of biodegradation and ozone treatment has recently been investigated to eliminate tannins and dyes to minimize wastewater pollution. Various fungal cultures such as Penicillium and Aspergillus niger are widely used for the biodegradation of many artificial colors and ryegrass extracts. Evidence shows that this hybrid model of biodegradation and ozone treatment is very effective in removing tannins and dyes. Combined with biodegradation, ozone treatment is superior to chemical methods due to its higher degradation rate. This coupling model minimizes contamination levels for various physical parameters such as BOD, COD, TOC, TSS, and TDS (Spier and Gutterres, 2019).

3.2.2 Use of bacteria for degradation of textile dyes A lot of microorganisms have been investigated, but the scientists did not find out the pigment-degrading bacteria. There have been numerous evaluations of bacteria that can degrade organic pollutants in the context of bioremediation (Ngulube et al., 2017). Microorganisms play an important role in the recovery of organic pollutants and are used as pollutants for various toxic substances in wastewater and require

Table 15.1 Biological methods for degradation of different dyes present in textile effluent (Holkar et al., 2016; Katheresan et al., 2018; Bhatia et al., 2017). Organisms

Dye

Mechanism

Advantages

Disadvantages

Efficiency

Fungal degradation

White rot fungus (Pleurotus eryngii) White rot fungus (Coriolopsis spp) Penicillium simplicissimum Aspergillus niger

Naphthalene

Fungi releases different enzymes that breakdown the dye molcules and use for their own growth

Fungi degradation allows to degrade a vast variety of dyes and considered as flexible method

More time required for self-growth, requires nitrogen fixed region and huge reactors for proper removal of dyes, lastly its unstable system

76.0%

Bacteria can be mixed with other bacteria or chemicals for efficient removal of dyes from wastewater, secondly a mixture of bacteria, fungi and algae can be used with different chemicals for removal of dyes

Bacterial degradation takes 30 h for efficient removal of dyes from wastewater, which is considered suitable, fast and reusable for removal of azo dye from wastewater

High cost, needs ordinary processes after treatment, produce colorless toxic by-products, sludge production, applicable to few dyes

80.0%

Bacterial degradation

Lichen (Permelia perlata) Proteus mirabilis LAG Kocuriarosea (MTCC 1532) Alcaligenes faecalis PMS-1 Enterobacter sp. F NCIM 5545 Bacillus cereus, B. megaterium Bacillus endophyticus Bacillus subtilis

Triphenylmethane dyes Triphenylmethane dyes Remazol brilliant blue R (RBBR) and acid red 299 (NY1) Disperse dye solvent red 24 Reactive blue 13 Methyl orange Reactive orange 13 Reactive blue 19 Azo dye red 3BN Acid red 128 Crystal violet

Continued

3. Methods of dye removal

Methods

337

2018; Bhatia et al., 2017).dcont’d Organisms

Dye

Microbial consortium

Reactive orange 16 Acid red 88, direct Red-81, reactive Black-5 Napthol green B, methylene blue Foron rubine RDGFL, foron black RD3GRN, foron turquoise SBLN, foron yellow RD5GL, foron blue RDGLN, foron red RDRBLS, Reactive blue 19; dark green dye, navy blue Reactive, remazol Red-198, reactive green-19 Light red dye, crystal violet Direct blue 80, congo red Crystal violet, congo red, direct blue 80, acid blue 113, basic red 46, direct brown 2, direct blue 151, remazol blue, indigo dye

Shewanella sp. Strain IFN4 Shewanella oneidensis MR-1 Ganoderma lucidum and Coriolus versicolor

Enterococcus spp

Proteus spp Klebsiella ozaenae Pseudomonas spp

Mechanism

Advantages

Disadvantages

Efficiency

CHAPTER 15 Biological methods for degradation

Methods

338

Table 15.1 Biological methods for degradation of different dyes present in textile effluent (Holkar et al., 2016; Katheresan et al.,

Klebsiella spp

Clostridium perfringens Rhodococcus rhodochrous Providencia spp

Burkholderia spp Ochrobactrum spp Acinetobacter baumannii Lysinibacillus spp

Reactive red 4E8Y5, reactive blue 172 Black WNN Crystal violet Reactive red 22 Reactive black Reactive blue 5 Provisional pink, drimarene red, methyl red and navy blue, Congo red, remazol blue Alizarin Remazol blue Congo red Reactive orange 4 Continued

3. Methods of dye removal

Paenibacillus alvei Enterobacter spp Pseudomonas luteola Pseudomonas entomophila BS1 Streptococcus thermophilus Bacillus spp

Acid blue 25, light red dye, reactive blue 19, dark green dye Crystal violet, mono azo dye Toludine red

339

340

2018; Bhatia et al., 2017).dcont’d Methods

Organisms

Dye

Micrococcus luteus

Remazol blue

Halomonas elongata Escherichia coli

Methyl red Methyl red, Congo red and DB 38, reactive dye red 22 Indigo dye

Stenotrophomonas spp Actinomyces spp Aeromonas jandaei Aeromonas hydrophila spp Staphylococcus spp

Algal degradation

Scheffersomyces spartinae Proteus vulgaris and Micrococcus glutamicus Green macroalga Xanthophyta alga

Cladophora species

Mechanism

Advantages

Disadvantages

Efficiency

Dye degradation is done due to use of dye ingredients by algae for selfgrowth

Eco-friendly process, less cost, easily approachable, can degrade wide variety of dyes by

Non-stable process

89.9%

Indigo dye Methyl red Provisional pink Indigo dye, congo red, evans blue, eriochrome black T azo dyes Acid scarlet 3R Azo dye scarlet R

Malachite green, basic red 46 Malachite green, triphenylmethane dye Malachite green

CHAPTER 15 Biological methods for degradation

Table 15.1 Biological methods for degradation of different dyes present in textile effluent (Holkar et al., 2016; Katheresan et al.,

Brown alga

Acid orange 7

Vaucheria species, Cosmarium sp

Malachite green, triphenylmethane dye Acid red 247 Acid red 27 Reactive red Malachite green Methylene blue Astrazon blue and red, Methylene blue Acid blue 9 (triphenylmethane) Methylene blue Red dye Methylene blue

Spirogyra rhizopus Shewanella algae Synechocystis sp. Pithophora sp. Cystoseira barbatala Caulerpa lentillifera

Spirulina platensis Ulva lactuca Blue green algae Caulerpa racemosa, Sargassum Desmodesmus sp. Azoreductase

DyP-type peroxidases Lignin peroxidase; Laccases;

Extracted enzymes from microbes used to degrade dye molecules through oxidation and reduction processes

Less cost, recyclable, less toxic, high output, uses enzymes from biological sources for degradation of dyes

Unreliable amount of enzyme production Enzyme production is not sure able process

90.1%

341

Continued

3. Methods of dye removal

Enzymatic degradation

Malachite green, methylene blue Acid red, reactive red BL, reactive red 141 Reactive blue 4, 5 and 19 Amaranth dye, navy blue HE2R Direct blue 14, novacron red, remazol black, amaranth dye, turquoise blue, navy blue, methyl orange

consuming for own growth

342

2018; Bhatia et al., 2017).dcont’d Methods

Organisms

Dye

Tyrosinase;

Amaranth dye, reactive black 5 (RB5), direct blue 71, reactive yellow 107 (RY107), reactive red 198 (RR198), reactive orange 13, navy blue HE2R

NADHeDCIP reductase; Riboflavin reductase

Amaranth dye, reactive orange 13 Amaranth dye, navy blue HE2R Direct blue 14, remazol black, turquoise blue, reactive red 195A, Reactive yellow 145A Reactive orange 13, Acid blue-25 (AB25) Methyl orange

Mn peroxidase

Veratryl alcohol Oxidase HRPO (horse reddish per oxidase) Soyabean peroxidase Luffa actangula peroxidase

Methyl orange

Mechanism

Advantages

Disadvantages

Efficiency

CHAPTER 15 Biological methods for degradation

Table 15.1 Biological methods for degradation of different dyes present in textile effluent (Holkar et al., 2016; Katheresan et al.,

Biosorption degradation

Saccharomyces cerevisiae Bacillus cereus C. tropicalis Enterobacter dissolvens, Pseudomonas aeruginosa Trametes versicolor and Trametes trogii Clavibacter michiganensis Nostoc linckia Neurospora sitophila Desmodesmus spp Aspergillus lentulus

Direct red 23 Malachite green Mixed textile effluent Acid red 119

Living organisms are mixed in such a way that adsorb dye substances and remove them from effluent

Degrade selected dyes having affinity for mixed microbial culture

Not good for all dyes, can degrade selective dyes

86.0%

Lanaset gray G Setazol blue BRF-X Reactive red 198 Basic blue 7 Methylene blue Malachite green Acid blue 120

3. Methods of dye removal 343

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CHAPTER 15 Biological methods for degradation

further study (Hruby et al., 2016). The main advantage of bacteria is that they grow more easily and grow faster than other microorganisms. The bacteria’s ability to break down dye can be easily improved through molecular genetic manipulation. Bacteria can degrade organic pollutants based on chlorine and aromatic hydrocarbons, which are degraded when used as an energy source (carbon source) (Pi et al., 2017) and dyes used which are made up of sulfur (Sulfur Blue 15) oxidized to sulfuric acid (Nguyen et al., 2016). Under traditional aerobic, anaerobic, and extremely anaerobic conditions, various bacteria cause a decrease in the azo dye content, which causes discoloration. The chemical reaction during the reduction of the azo dye begins with the cleavage of the azo bond by azo reductase in an anaerobic medium (-N) ¼ N-), then after this, aromatic amines colorless solution is formed (Mendes et al., 2015). Bhatia et al. (2017) stated that azo compounds are used as a medium for the growth of aerobic bacteria. Sulfonated amine is decomposed aerobically. Table 15.1 shows the various dyes and bacteria species that have the potential to degrade the dye. Pseudomonas putida, Proteus, Bacillus subtilis, Pseudomonas aeruginosa, and Clostridium perfringens are gram positive bacteria have been shown to effectively degrade many fibrous azo dyes with different structures. In the same way, gram negative bacterial strains include Enterococcus, Klebsiella pneumonia, and E. coli gives decolorizing effect. This section shows that some studies have shown the ability to identify the bacteria which are present in water and in the soil respectively, for the biodegradation of fibrous wastewater. Further research should focus on this important area of microbiology for solving problems in an industrial environment.

3.2.3 Degradation of dyes by use of anaerobic and aerobic cultures Typically, aerobic, anaerobic, and facultative anaerobic bacteria (which can survive in aerobic or anaerobic environment) are used to break down dyes. Compared to anaerobic and facultative treatments, all aerobic processes produce sludge. Bacterial decomposition of basic azo dyes is caused by the breaking of azo-bonds (-N) ¼ Ne-) by azo-reductase in anaerobic environment, forming the effect of destruction of azobonds (-N) ¼ N-). Colorless and toxic intermediates can result from aerobic or anaerobic processes that are then processed (Palani et al., 2012). With regard to pigment degradation, Aspergillus Red 78 degraded by bacteria (Pseudomonas spp strain SUK1) with percentage of 37 is higher than the fungal culture (Aspergillus ochraceus NCIM 1146) (Lade et al., 2012). Sultana et al. (2015) reported that the restoration of azo bonds is possible to be more degraded in the ideal aerobic environment. Khan et al. (2013) stated that organic carbon energy is needed for the decomposition of such dyes in water in case of anaerobic conditions. It can be a cheapest way likewise C6H12O6, C2H3O2, or a composite compound like tapioca flour, which are best used to fulfill the requirement of anaerobic activity in discoloration process. Table 15.1 shows a large number of anaerobic bacteria that subsequently release amines, breaking azo bonds caused by the action of specific oxidases and reductases.

3. Methods of dye removal

In recent past years, several types of bacteria have been distinguished that can discolor azo dyes in an aerobic environment (Table 15.1). Palanivelan et al. (2014) discussed that several bacterial type need carbon that is produced organically as an energy source for their growth. However, it was reported that some bacteria can survive even with azo complexes, since they are used as a carbon source (Bhatia et al., 2017). Enzymes contained in bacteria break the eN) ¼ N bond that is the reason of formation of amines. The amine is used as a carbon source and as energy source for the development. Such kind of bacterial species are very delicate to substrates. Xenophilus is known as such type of specie. Four types of bacteria have been evolved that use methyl red to fulfill the requirement of carbon. Two of these strains are Vibrio logei and Pseudomonas nitroreducens. The presence of amine products in the growth medium was not evaluated, which indicates the degradation of the medium (Bhatia et al., 2017). Table 15.1 highlighted the corresponding bacterial spp. in aerobic environment. This research data show the probability of evolving the suitable types for the development of bioreactors for fiber wastewater treatment. You can test the reproducibility of wastewater treatment with a single bacterial culture. It has been observed that flora is primarily beneficial because it can perform degradation tasks together and cannot effectively initiate the cultivation of individual bacteria (Saroj et al., 2015). In a diverse culture system, the synergistic effect regarding the metabolic activity of the bacterial community increases the degree of pigment biodegradation and calcification. In the diverse culture system, one bacterial colony attacks different positions in the dye substance or ingests transitional metabolites that are composed by another bacterial species, which is present to replace the decomposed dye. However, its disadvantages are that the bacterial consortium can only deliver an moderate macroscopic understanding of biodecomposition, the outcomes of degradation cannot be reproduced, and an effective description of the biodegradation system is very difficult. Due to its high biodegradability, the bacterial consortium is of great interest for the decomposition of azo dyes from the water which is disposed of. Numerous research data on the decomposition of dyes in textile water using the microbial consortia. Also note that several researches performed with synthetic water may not be replicable when recycled with actual wastewater-containing several types of compounds (surfactants, salts, dressings, finishes, etc.). Thus, this work should be applied to the decomposition of dyes of interest in real wastewater using the specified individual bacteria or a bacterial consortium.

3.2.4 Algal degradation of dyes Algae mostly grow in fresh and marine water and are widely studied as bioadsorbents (Devi et al., 2015; Gupta et al., 2014). Because algae have a high surface-binding capacity, they have the maximum bioadsorption capacity and the maximum electrostatic desirability to contaminants, which are found in wastewater. Several studies have exposed that there are many types of pollutant metabolites in wastewater like eOH, RCOO-, eNH2, which are engaged onto the exterior part of algae (Al-Fawwaz and Abdullah, 2016).

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There are three different mechanisms involved in the decomposition of dyes that is done by algae. First of all, algae consume chromophores to produce algal biomass, carbon dioxide and water. And then the alga facilitates the transformation of chromophores into nonchromophores, while at the third phase, as the result of chromophore formation are consumed by the algal biomass (Alvarez et al., 2015). Many studies (Table 15.1) have shown that algae effectively use the degradation of azo dyes, producing azo reductase for discoloration (Thirumagal and Panneerselvam, 2016; Pathak et al., 2015). Several studies have reported on the species of algae, for example Chlorella pyrenoidosa degrade methylene blue, Spirogyra rhizopus for acid red 247, Cosmarium spp, Pithophora spp, Nostoc Muscorum (cyanobacteria), Ulva lactuca, Sargassum, and Desmodesmus spp. efficiently decompose the azo dyes into aromatic amines and further change this in the form of organic compounds. Other research data stated that algal types utilize azo dyes for carbon and nitrogen sources for algal growth (Waqas et al., 2015). The literature also suggests the presence of large green algae, the Cladofora species (Holkar et al., 2016), have the ability to remove azo dyes due to the release of azo reductase enzyme. Li et al. (2014) decolorized the azo dye (Acid Red 27) from Shewanella algae (SAL) in the existence of maximum absorptions of NaCl and several quinones or humic acids. This research data elaborate that color change arbitrated by acid red 27 can lead to the formation of aromatic amines, which are less toxic to health. Dehghan and Niaei (Dehghan and Niaei, 2013) stated that decomposition of red dye 46 by the use of Enteromorpha spp, a large green algae. So that algal biomass has important role in elimination of azo dyes from fibrous wastewater by decomposition.

3.2.5 Role of enzymes in degradation of textile dyes from wastewater Enzymes are the functional substances that mostly break down complex substances one at a time. It was found that some bacteria contain nonspecific cytoplasmic enzymes that act as azo reductase (Dave et al., 2015). Table 15.1 shows enzymes that degrade fiber dyes, such as acid red or reactive BL are degraded by azo reductase. Laccases for amaranthe dyes, Direct Blue 14, Methyl Orange, Novacron Red, and horseradish peroxidase are used to for Acid Blue 25 from many origins. Mendes et al. (2015) described an enzyme called azo reductase, which breaks the link of the azo group and triggers a catalytic reduction reaction that makes aromatic amines to the neutral water. Many research reports indicates the use of bacterial cytoplasmic azo reductase in ecological biodiversity (Shah et al., 2013). Azoreductases can be divided according to contented of rare primary protein sequencing (Morrison et al., 2014). Phenol oxidase or laccase has great potential to break down many aromatic waste products. These laccases can break down a complex polyaromatic polymers called lignins. Laccase is also a member of several copper oxidases and belongs to the category of oxidoreductases that can oxidize phenols and its compounds by eradicating electrons. The performance of laccase was examined at acidic pH in a fungal strain (Pla´cido et al., 2016; Leeza and Sharma, 2014). Manganese peroxidase is known as enzyme that belongs to the class

3. Methods of dye removal

oxidoreductases. Lignin peroxidase merge with nonphenolic methoxy-substituted lignin subunits that act as substrates, while it attacks phenolic compounds with an intermediate redox chemical reaction with Mn2 þ /Mn3 þ ions (Hosseinzadeh et al., 2016). Laccase uses an essentially nonspecific radical mechanism to break down azo dyes without producing harmful aromatic amines. Trametes versicolor decolorizes the orange G-azo dye by 97% (Yemendzhiev et al., 2011). Effective results were obtained using laccase (obtained from the Pseudomonas desmolyticum strain NCIM2112) and showed that complete decomposition of dyes such as Direct Blue 6 and Red HE7B (Rokade and Mali, 2013). All previous research data highlight the part of several enzymes contribution in the removal of many waste products and compounds from industrial water. If certain enzymes enter the aquatic environment during the purification process, the research data have not been led down to define the lasting effects on marine organisms in the marine environment. So that there is a need of more accurate and detailed research work to treat the waste water and management of aquatic life and ecosystem.

3.2.6 Biosorption assay for textile dye degradation The utilization in amalgamation with biological material is another method for the biological utilization of fiber dyes. Although there are many studies of the degradation of fiber dyes by various methods, there are few documents on the utilization of microbial cultures immobilized on suitable substrates. In this era, researchers have tried to use agricultural waste such as straw, cotton, pine needles, cake, cashew nut shells and fungal yeast cells (Bhatia et al., 2017). Bacterial biomass and algal biomass for the utilization of textile water in order to reduce costs and reduce the stages of treatment of such biological materials (Siddique et al., 2017). The biological limits of microbial adsorption are due to heteropolysaccharide belonging to azo dyes and their biochemical components. The viability of a biological solution depends on additional conditions, like pH value, heat, ion mass, dye structure, and microbe type (Bhatia et al., 2017). Various biological adsorbents for the elimination of colorants from wastewater are mentioned in Table 15.1.

3.2.7 Microbial fuel cell (MFC) technology for biodegradation of dyes The oxidation of several organic components of the fibrous wastewater by electrochemically triggered microbes in the microbial fuel cell (MFC) via the generation of the positive charges (protons) and the negative charges (electrons) in the anode chamber to produce water molecules by the reduction of oxygen. A separating membrane between the positive terminal (anode) and the negative terminal (cathode) is present in the MFC (Li et al., 2014). The external resistance between the anode and cathode makes it easy to collect the generated electrical energy. Research into MFC components (such as electrode membranes and microorganisms) is still in its infancy. The main disadvantage of the MFC is its application at the massive scale because of the small scale energy production and costly MFC substances. More the last 15 years, there has been a lot of effort to improve MFC

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power generation. Recent studies have reported on various structures, membrane and electrodes (cathode-anode), microorganisms communities, and fibrous wastewater substances comprises of the azo dyes that are used to produce energy in MFC (Holkar et al., 2016). However, the membranes (Nafion), the anodes (carbon cloth or carbon paper), and the cathodes made of (platinum) used are costly and delicate. To achieve various types of wastewater treatment in practical applications such as wastewater treatment, bleaching, dyeing and printing, it is obligatory to develop MFC with higher amplitude of energy or power, economical electrodes and membrane constituents, and excellent scalability. Recently, activated carbon and modified carbon nanofibers were frequently used as anodes but their higher internal resistance (HIR) can be linked with film formation or large pore sizes. If you exceed this limit in the future, you can improve performance even further. By using a multiwalled carbon nanotube (MWCNT)-SnO2 coating on a granular carbon electrode (GCE), an improved stability, performance, and charge transfer resistance can be achieved in nanotubes. Most of the constituents used for the anode assembly are of higher carbon resistance (Mehdinia et al., 2014; Anwar et al., 2017). In future, the resistance can be minimalized by using edge metal collectors such as Cu, TiO2, Ni and Si. Therefore, the use of carbon-based composite materials, including inexpensive electrocatalysts (e.g., Cu, TiO2, Ni, Si), appears to be a favorable material for anode, but it requires further investigation. Recent discoveries in the cathode field have also focused on using carbon nanofibers/nanotubes to increase surface area. Song et al. (Song et al., 2015) conducted a study on Co3O4/nanocarbon composites and the results were nearly consistent with Pt/C performance in all aspects including columbic efficiency, reduced peak current, and power density (Song et al., 2015). If a suitable hybrid catalyst is found so far, the performance of carbon nanofibers and Pt/C electrodes can be expected to match or even better. Therefore, it is necessary to replace the carbon nanofiber cathode with a more efficient and inexpensive MFC catalyst. A combination of nanofiber composites with cheap catalysts (cobalt, iron, manganese dioxide, silver, palladium, etc.) seems to be a promising cathode material, but before declaring itself a more detailed problem. The range of MFCs used in industry is largely dependent on low resistance, high selectivity, low cost and long term membrane stability. MFC uses membranes to allow the transfer of ions from one chamber to another. The high ionic conductivity associated with liquid KOH and phosphoric acid is used in thick films such as sulfonated aromatic sulfonic acid polysulfone, and sulfonated polyether ketone (Ayyaru and Dharmalingam, 2014). In addition, electricity generation can be achieved by making materials such as ceramics and clay pots more porous and reducing electrical resistance (Daud et al., 2015). If cheap films like the one mentioned above interfere with proton transfer in the presence of other cations due to size differences will be an important achievement for MFC. However, this does not solve the problem of selectivity. Cationic compounds present in fibrous wastewater such as potassium, sodium, calcium, ammonium, and magnesium can pass through the Nafion membrane like protons. Given that the concentration of

3. Methods of dye removal

these cationic substances in the MFC is higher than the concentration of protons, the accumulation of these cationic substances occurs in the cathode chamber, which leads to an increase in the pH of the previous chamber and the pH will fall in cationic chamber. As a result, the efficiency of MFC decreases due to a decrease in microbial activity and a decrease in the thermodynamic potential of cells (Herna´ndezFerna´ndez et al., 2016). Thus, changing the pore size of the membrane ensures that only protons move and other cations do not. Various methods have also been proposed. That is, a cation exchange membrane (CEM) or anion exchange membrane (AEM) is used to solve the problem of pH gradients on both sides of the membrane (Leong et al., 2013). An ionic liquid membrane (IL) can open up this area of MFC improvement. Here, the ionicity of the IL ensures that only protons are selectively transported and no other cations cross the membrane. This can lead to an increase in the efficiency of the MFC, since cations that are not present in the fiber wastewater are transported through the membrane and do not affect the microbial activity in the anode chamber. Consequently, energy can be obtained from textile wastewater, which is about of five folds power in contrast to the energy consumption for wastewater treatment (Xie et al., 2011).

3.2.8 Biofilm technology for recycling of wastewater Of all biological methods, biofilm technology played a vital role for recycling of wastewater (Sehar and Naz, 2016). The biofilm consists of several microbial communities combined with an extracellular polymer substances (EPS) matrix (Naresh Yadav et al., 2020). Biofilm development is divided into five important stages: (1) plankton microorganisms attach to each other as quickly as possible on a hard surface or in an aquatic environment; (2) EPS, regulated by microorganisms, is completely fixed as polyhydroxy groups, and these polyhydroxy groups are captured by hydrogen bonds with the bacterial surface (Donkadokula et al., 2020); (3) by replicating the original colony forming device on a solid surface, a thin layer of small colonies was made during the development of the adhesive or suspension; (4) combine them using new planktonic bacteria: environmental debris transforms the biofilm into a three-dimensional shape; and (5) using passive and active methods, the matrix covering the biofilm is transformed through the biofilm into airborne bacteria to achieve diversification or diffusion of intercellular signaling programs (Donkadokula et al., 2020). Factors influencing biofilm formation include nutrients, pH values, temperature, carrier surface topology, velocity, turbulence, hydrodynamics, EPS formation, and divalent cations (Ansari et al., 2017). A solid carrier medium (SSM) is included in the slurry reactor to disperse the adhesive surface for biofilm development. The addition of SSM can increase the concentration of microorganisms and can also degrade contaminants (Donkadokula et al., 2020). Various microorganisms present in the biofilm matrix break down carbonaceous substances, phosphorus, entrained pathogens, nitrogen compounds and nutrients in wastewater. The advantages of biofilm treatment plants are operational flexibility,

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smaller footprint, shorter hydraulic fluid retention times, lower environmental impact, increased biomass weight, reduced sludge formation, and shorter biomass retention times, expansion, and excellent technological potential, breaking down complex bonds (Martin and Nerenberg, 2012). Mineralization of Acid Orange 7 (AO7) with a batch sequencing reactor using a granular activated carbon biofilm formulation. Many biofilm producing bacterial strains such as Bacillus cereus strains, Bacillus pumilus strain, Brevibacillus panacihumi strain, and Lysinibacillus fusiformis strain used for biodegradation of toxic dyes frequently found in textile wastewater (Donkadokula et al., 2020).

4. Conclusion The presence of colorants in the surrounding water is one of the reason of water contamination. To get rid of this situation, effective dye elimination methods should be used to treat the dye before it is released into the surroundings. Discharge of wastewater into the environment with the lowest possible pollutant content should be the goal of dye decontamination plants around the world. The printing and dyeing industry is responsible for draining wastewater to acceptable standards. The industry needs to consider reusing wastewater without dyes as a water source. This process should not be used in wastewater treatment plants because it is known that traditional processes do not remove all colorant particles. This chapter describes many biological techniques and their effectiveness in removing biological pigments. The above processes can be used to remove dyes from wastewater. These can significantly reduce the pollution of the water emitted by the dye industry. Most of the colorant removal methods described attempt to remove over 80% of the colorant particles from the wastewater, but some methods remove 90% of the colorant particles from the wastewater. Wastewater treatment plants that use biological methods rather than chemical ones prefer to produce less inorganic sludge by biological methods, lower operating costs and complete dye salinity/stabilization. In general, the parameters of the textile wastewater after biological treatment do not meet the standards for the discharge of dyes wastewater from the fiber. Biological treatment methods or techniques using natural bacteria have been found to be economically viable, harmful to the environment and socially acceptable. Both free and fixed conditions (green algae) can be effectively used as bioadsorbents to decolorize methylene blue and malachite green dyes. The use of various types of enzymes and enzyme complexes has also shown the possibility of removing pollutants from wastewater from the textile industry. In the end, the general conclusion of this chapter is that there are still some viable microbiological methods for treating industrial wastewater. Consequently, further research is needed on the use of these technologies to ensure the sustainability of aquatic organisms in various ecosystems of the earth.

References

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Biodegradation of azo dye using microbiological consortium

16

Chitra Devi Venkatachalam1, Mothil Sengottian2, Sathish Raam Ravichandran2, Sivakumar Venkatachalam3 1

Department of Food Technology, Kongu Engineering College, Erode, Tamil Nadu, India; Department of Chemical Engineering, Kongu Engineering College, Erode, Tamil Nadu, India; 3 Department of Chemical Engineering, AC Tech Campus, Anna University, Chennai, Tamil Nadu, India 2

1. Introduction Dyeing of fiber, yarn, and fabrics using natural dyes and pigments have been an age old process that dates back to thousands of years. These natural dyes were extracted from plant parts (leaves, fruits, berries, bark, and roots), lichens and insects, etc. (Mansour, 2018). Some of them include Mountain Alder (Alnus incana), Bloodroot (Sanguinaria canadensis), Rubber rabbitbrush (Ericameria nauseosa), Smooth sumac (Rhus glabra), Canaigre dock (Rumex hymenosepalus), Butternut (Juglans cinerea), etc. During dyeing these pigments were mixed with water-soluble chemicals, usually metallic salts (aluminum, iron, copper, tin, and chromium) as mordants that help in fixation of the dye onto the fabric (Moody and Needles, 2004). Although the natural dyes were environmental friendly, they also had several disadvantages such as not proper availability of natural dye in ready-to-use form, not user friendly, and unsuitable for machine use. The most important disadvantage is that they gave limited and nonreproducible shades with another problem of plants exploited for food, feeder and a danger of extinction of endangered forest species was a concern (Saxena and Raja, 2014). As the industry evolved and after the first synthetic dye discovery in 1856 made the industry to grow at a faster rate. The simplicity in use of synthetic dyes with its easy reproducible and ultraviolet fasting colors made it sustainable in the global market. Synthetic dyes are classified based on their chemical composition by American Association of Textile Chemists and Colorists (AATCC) as acid dyes, azoic (naphthol) dyes, basic (cationic) dyes, direct (substantive) dyes, disperse dyes, pigment dyes, reactive dyes, sulfur dyes, and vat dyes (Benkhaya et al., 2020a,b). The main advantage of synthetic dyes over natural dyes are that they are less expensive, produce better color fastness, and have a wide variety of shades, which are classified with Color Index constitution number (CI number; Kumar Gupta, 2020). There are several methods of dyeing of fabric and yarns based on their properties. Vat dyeing is Development in Wastewater Treatment Research and Processes. https://doi.org/10.1016/B978-0-323-85657-7.00017-1 Copyright © 2022 Elsevier Inc. All rights reserved.

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the form of dyeing where the fabric are treated in dye bath, i.e., in a large vessels or vat and on exposure to oxygen in air, the dye molecules entrapped in the fiber pores oxidize and regenerate color. Direct dyeing is done where the fabric are wettable and thereby they are immersed into a hot aqueous solution of dye and treated with solution of metallic salts or mordants for the fastness. Disperse dyeing is the process where the impregnation of dye into the hydrophobic synthetic fibers like acrylics, acetate rayons etc., is less and so it is dyed in a boiling dye bath at 120e130
C with carriers like benzyl alcohol or biphenyl (Tyrone, 1994). In either way, during the dyeing approximately 10%e15% of the dye used is nonbound and residual in the bath effluent and it is rejected as wastewater into the water bodies without the series of steps for treatment (Pandey et al., 2007). These chemical contaminants in the water bodies cause serious environmental and health problems. The high concentration of these dyes curtails the reoxygenation capacity of water and cuts off the sunlight, thereby affecting the process of photosynthesis in aquatic plants and algae (Petsas and Vagi, 2017). Also these dyes accumulate in the living cells of the aquatic organisms including fishes and on death and decomposition release various types of carcinogenic and mutagenic compounds into the water making it unfit for consumption (Samchetshabam et al., 2017). This chapter deals mainly with the use of azo dyes in the textile industry, its impact on environment and different methods involved in the treatment of azo dyes. It also focuses on the microbial degradation of azo dyes and its biodegradation effect using single organism or a microbiological consortia. The effect of the process parameters during the bioremediation through microbial treatment is also discussed in detail.

2. Azo dyes in textile industry Azo dyes constitutes one or more eN¼Ne groups and are the most widely used synthetic dye in commercial applications such as textile, cosmetics, printing industries, etc. Azoic dyes are produced by a reaction between two components reaction between diazotization salts with functional group ReNþ2X and coupling reaction that are rich in electrons, i.e., phenol, aniline, etc. The generalized reaction involved in the synthesis of the diazotization salts and with the coupling agent is given in Fig. 16.1 and this is called as electrophilic aromatic substitution mechanism. The classification of azo dyes, its impact on environment and the various methods to degrade are to be studied in detail.

2.1 Classification of azo dyes Azo dyes can be classified based on the Color Index as monozo (11000e19999), disazo (20000e29999), trisazo (30000e34999), poly azo (35000e36999) and azoic (37000e39999) dyes. There are both symmetric and asymmetric azo dyes which can be classified also based on the chemical groups present (hydrazine, chromene) and the parent chemical group (2-aminothiophene and 2-aminothiazoles). Some of the azo dyes based on their color are given in Table 16.1.

2. Azo dyes in textile industry

FIGURE 16.1 Synthesis of azo dye (Benkhaya et al., 2020a,b). Adapted from Benkhaya, S., M’rabet, S., El Harfi, A., 2020b. Classifications, properties, recent synthesis and applications of azo dyes. Heliyon 6 (1). Cell Press e got rights for reprint-license number (4975910517780). https://doi.org/10.1016/j.heliyon.2020.e03271.

2.2 Impact of textile effluents containing azo dyes on environment The dyes when let out as effluents into the environment they interact with the ecosystem and produce larger impact over the living organisms. The environmental conditions i.e., interaction with water, soil, air and certain microbes lead to the formation of toxic metabolites which on consumption causes severe health defects (Cavicchioli et al., 2019). Some of the toxic moieties from the azo dyes that causes ecotoxicity are Benzedine, Benzene-1,2,4-triamine, Aniline from Direct black 38; Naphthalene-1,2-diamine, Naphthalene, Benzedine from Congo Red; 3,30 -Dimethoxybenzedine from Direct Blue 1, 1-Amino-2-naphthol, 4-Amino-benzenesulfonic acid from Acid Orange 7, Sunset Yellow, Acid Orange 52, Direct Orange 39; and 1,3,5-Triazine, Naphthalen-2-ylamine from Reactive Red 195, etc. (Rawat et al., 2016). They have a larger impact on aquatic lives i.e., in fish causes deviation in ionic regulations in sensitive tissues like liver, kidney and muscles by increasing concentration of sodium and chloride and increasing the concentration of potassium, calcium, and magnesium ions; in algae it affects growth by resisting protein level in tissues and also decreases nutrient uptake by altering the morphological characteristics (Samchetshabam et al., 2017).

357

358

Azo dye/ pigment Trypan blue Direct blue 1

Direct blue 71 Basic red 18 Direct red 28 Pigment yellow 12 Acid orange 7 Direct brown 78

CI number

CAS number

Molecular formula

Application

23850

72-57-1

C₃₄H₂₄N₆Na₄O₁₄S₄

Trichrome staining and to assess cell viability

24410

261005-1

C34H28N6Na4O16S4

Dyeing textiles with high contents of cellulose, i.e., cotton

34140

439955-7 2519822-5 573-580

C40H23N7Na4O13S4

21090

635885-6

C32H26Cl2N6O4

Used for staining membrane-immobilized antibodies and proteins Used for coloring textiles, leather, acrylic fibers Used to dye cotton, stain tissues for microscopic examination, calico printing and dyeing paper Used in industrial paints, printing inks, textile printing

Orange II, Persian orange, acid orange A, Colacid orange

15510

633-965

C16H11N2NaO4S

d

40290

265018-2

C37H37N2O9S3

Synonyms Benzamine blue, Niagara blue, Diamine blue Airedale blue FFD, Amanil sky blue 6B, Amanil sky blue FF, Atlantic Resin fast blue Sirius light blue BRR, Solantine blue FF Aizen Cathilon red GTLH, Astrazon red GTL Atlantic Congo Red, Atul CongoRed, Azocard Red Congo, Benzo Congo Red Benzidine yellow, Diarylanilide yellow

26457 22120

C19H25Cl2N5O2 C32H22N6Na2O6S2

Used for dyeing of wool, silk and polyamide fiber fabric of direct printing, as indicator and biological shading Used for dyeing textile fabric, yarn

CHAPTER 16 Biodegradation of azo dye using microbiological consortium

Table 16.1 Azo dyes examples based on color.

3. Microbiological degradation of azo dyes

2.3 Different methods used in degradation of azo dyes In general, the wet processing in textile production produces most of the effluent and damage to the environment. Textile waste water can be treated by chemical methods such as coagulation and flocculation, electrocoagulation, advanced oxidation process, Fenton’s reagent, ozonation, photochemical and photocatalytic degradation, electrochemical destruction; physical methods such as adsorption, membrane filtration; and biological methods such as aerobic treatment, anaerobic treatment, anoxic treatment, and sequential degradation (Madhav et al., 2018). Tannery dye bath effluent consisting of azo dyes Acid Black 210 and Acid Red 1 were treated using electrocoagulation using AleFe electrodes and obtained 65% e70% reduction of COD, BOD5, and TDS (Mothil et al., 2019). Advanced oxidation process can be used as an alternative where acid black was treated under O3, O3/UV, and O3/Fe (II); Orange II decolorization using Tungsten Oxide nanoparticle modified carbon in presence of H2O2; and Direct Red 83:1 degradation using pulsed light and H2O2 in salt water (Rekhate and Shrivastava, 2020). Methyl Orange, which is the simplest form of azo dye is degraded using PdNCs embedded alpha-Fe2O3 by Fenton-like catalytic reaction, while natural clay is used as adsorbent for treating textile waste water (Venkatachalam et al., 2019, Senthilkumar et al., 2018). Since the development of new design in membrane modules, reverse osmosis (RO) and nanofiltration (NF) are the membrane techniques extensively used in treatment of industrial textile effluents and for reuse of water (So´jka-Ledakowicz et al., 1998). A study shows that for dye concentration 65 mg/L, feed temperature ¼ 39
C and at pressure ¼ 8 bar RO membranes gives a removal percentage of 97.2%, 99.58%, and 99.9% for acid red, reactive black, and reactive blue dyes; while NF membrane gives a removal percentage of 93.77%, 95.67%, and 97% for red, black and blue dyes, respectively (Abid et al., 2012). Although there are many methods for treatment of the dye effluents, biodegradation of these azo dyes is very important because the conventional physical and chemical methods result in production of further refractory pollutants, i.e., for incineration. This biological treatment of dye wastewater are the hope to provide clean, ecofriendly, efficient, and low-cost solution.

3. Microbiological degradation of azo dyes Microbes form an integral part of the human life and maintain the balance in the ecosystem to convert complex substances into their simple form and give it back as supplement to the growth of the living organisms higher in the hierarchy, especially plants (El-Ramady et al., 2014). Some of the good microbes about 1000 bacterial species inhabit the gut of human beings helping in metabolism of dietary components (Rowland et al., 2018). Thus microbes can be utilized as a tool on bioremediation of dye effluents and degradation of azo dyes both through aerobic and anaerobic pathway. Anaerobic degradation of azo dyes result in aromatic amines

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CHAPTER 16 Biodegradation of azo dye using microbiological consortium

and few hazardous byproducts, while aerobic degradation involves production ecofriendly toxic-free organic metabolites (Ajaz et al., 2020). Yet there is a vast untapped potential from microbes and there are several mechanisms that need further study, which vary from species to species. These microbes include bacteria, algae, and fungi.

3.1 Degradation mechanism with bacteria The aerobic degradation of azo dyes with bacteria like E. coli producing azo reductases that slices the azo link eN¼Ne resulting in amines, which are harmful, mutagenic and carcinogenic for the species in the ecosystem where it is released. These need to be further mineralized by the microorganisms generating small length acids and aldehydes (Popli and Patel, 2015). Under anaerobic conditions, the azo reduction is simple and involve some of the redox intermediates or cofactors such as FADH2, FMNH2, NADH, and NADPH which transfer the electrons to the azo bond thereby converting the larger dye molecule into two aromatic amines with hydroxyl and carboxylic acid functional groups (Mahmood et al., 2016). While in enzymatic catalyzed processes, similar to the aerobic process where azo-reductase is involved in the electron transfer and cleavage mechanism which is shown in Fig. 16.2. There are some studies where the azoAzo Dye

Amines

X

Chromophore

N

X

N

NH2

Redox Mediator Oxi

Redox Mediator Red

NH2

Azoreductase X NADH Carbon Source (e- donar)

NAD+

X Oxidation Product

Dehydrogenase

Bacterial Cell

FIGURE 16.2 Proposed mechanism inside bacterial cell for degradation of azo dyes (Singh et al., 2015). Adapted from Singh, R.L., Singh, P.K., Pratap Singh. R., 2015. Enzymatic decolorization and degradation of azo dyes - a review. Int. Biodeterior. Biodegrad. 104, 21e31. Elsevier e Got rights for reprint-License Number (4987440489231). https://doi.org/10.1016/j.ibiod.2015.04.027.

3. Microbiological degradation of azo dyes

dye degradation using resulted in bioenergy production using microbial fuel cell (Mishra et al., 2020). Acid Orange degradation was performed by oxidative reductive mechanism where bacterial mediated anode (Shewanella oneidensis) reduction and enzyme mediated cathode (Laccase) oxidation resulted in only 20% dye decolorization at anode 80% dye decolorization at cathode with power density 50  4 mW/m2 (Mani et al., 2019). Dye degradation and its percentage decolorization for Reactive Black B and Congo Red using bacteria such as Bacillus subtili, Bacillus cereu, Bacillus licheniformis, and Pseudomonas sp. are given in Table 16.2.

Table 16.2 Azo dyes decolorization using microbes. Dyes decolorized

Decolorization (%) 83 72

Gomaa (2016)

65 84

Gomaa (2016)

60 86

Gomaa (2016)

62 85

Gomaa (2016)

100 88 80 79

Jinqi and Houtian (1992)

A

Reactive black B Congo Red Reactive black B Congo Red Reactive black B Congo Red Reactive black B Congo Red Direct blue 71 Direct red 23 Direct orange 26 Direct black 19 Congo Red

99

A

Congo Red

98

A

Congo Red

97

A

Congo Red

89

A

Congo Red

52

A

Methylene blue

84

F

Procion violet H3R procion red HE7B

69.3 80.6

Mahalakshmi et al. (2015) Mahalakshmi et al. (2015) Mahalakshmi et al. (2015) Mahalakshmi et al. (2015) Mahalakshmi et al. (2015) Mokhtar et al. (2017) Corso and Maganha De Almeida (2009)

Species

Type

Bacillus subtili

B

Bacillus cereu

B

Bacillus licheniformis

B

Pseudomonas sp.

B

Chlorella vulgaris

A

Chlorella vulgaris Haematococcus sp. Scenedesmus quadriquada Scenedesmus officinalis Scenedesmus obliquus Euchema Spinosum Aspergillus oryzae (non-autoclaved biomass)

References

Continued

361

362

CHAPTER 16 Biodegradation of azo dye using microbiological consortium

Table 16.2 Azo dyes decolorization using microbes.dcont’d Species

Type

Aspergillus oryzae (Autoclaved biomass) Coriolus versicolor (MTCC 138) Phanerochaete chrysosporium (MTCC 787) Pleurotus ostreatus (MTCC 142) Myrothecium verrucaria (MTCC 158)

F

F F

Dyes decolorized

Decolorization (%)

Procion violet H3R procion red HE7B Cibacron yellow S-3R Cibacron yellow S-3R

78.9 80.5 92 90

References Corso and Maganha De Almeida (2009) Chitradevi and Sivakumar (2011) Chitradevi and Sivakumar (2011)

F

Cibacron yellow S-3R

82

Chitradevi and Sivakumar (2011)

F

Cibacron yellow S-3R

85

Chitradevi and Sivakumar (2011)

A, Algae; B, Bacteria; F, Fungi.

3.2 Degradation mechanism with algae Algae are main source for many enzymes such as D6-Desaturase, acetyl-CoA synthetase, acyl-CoA diacylglycerol acyltransferase 1, and glucose-6-phosphate dehydrogenase, from species Phaeodactylum tricornutum, Chlamydomonas reinhardtii, Chlorella ellipsoidea, and Phaeodactylum tricornutum respectively (Vingiani et al., 2019). It can be also used to produce azo reductase which is used in the degradation of azo dyes. Azo reductase is extracted from the algal cells (Chlorella vulgaris, Nostoc lincki) by treating by washing with Phosphate buffer (0.03 M) followed by cold ultrasonic high speed cell disruption at 12,000 rpm for 1 h. The nucleic was removed by soaking it with using 5% protamine sulfate; also the activity of azo reductase was increased by addition of p-ammonio azo benzene (El-sheekh et al., 2009). Dye degradation and its percentage decolorization for Direct Blue 71, Direct Red 23, Direct Orange 26, Direct Black 19, Congo Red and Methylene Blue using algae such as Chlorella vulgaris, Haematococcus sp., Scenedesmus quadriquada, Scenedesmus officinalis, Scenedesmus obliquus, and Euchema Spinosum are given in Table 16.2.

3.3 Degradation mechanism with fungi Fungi a symbiotic organism play an important role as a decomposer and are involve in nutrient cycle as an effective recycler has a major contributor to the ecosystem. They are different from bacteria and algae as they can act as both adsorbent and enzyme mediated degrader in decolorization of azo dyes. They have the ability to produce extracellular ligninolytic enzymes like laccase, manganese

3. Microbiological degradation of azo dyes

peroxidase and lignin peroxidase which help in enzymatic decolorization of azo dyes (Sen et al., 2016). Some of the fungal species used for dye degradation are given in Table 16.2.

3.4 Advantages of using microbiological consortia In decolorization of Orange II the microbial consortia of Enterobacter cloacae and Enterococcus casseliflavus showed 100% decolorization while individually they can achieve only 10% and 23% respectively (Chan et al., 2011). While they decrease the time consumed for the process where 100% decolorization was observed within 3 h for microbial consortia of Proteus vulgaris and Micrococcus glutamicus which took 14 and 20 h, respectively (Saratale et al., 2009). A synergic effect is always observed when microbiological consortia were used not only for azo-dye decolorization but also for numerous biotechnological applications. Some of the examples of microbiological consortia and dye decolorization are given in Table 16.3.

Table 16.3 Microbiological consortia and dye decolorization. Species used in the consortia

Dye decolorized

Decolorization (%)

Procion green Direct blue Procion navy blue Congo Red Methyl red Reactive blue

81.5 83 82

Senan and Abraham (2004)

67.6 81.3 54.8

Krishnamoorthy et al. (2018)

B and B mix

Congo Red Methyl red Reactive blue

96.4 73.2 79.4

Krishnamoorthy et al. (2018)

B and B mix

Congo Red Methyl red Reactive blue

96.2 73.4 84.6

Krishnamoorthy et al. (2018)

F and F mix

Congo Red Methyl red Reactive blue

97.4 87.1 90.6

Krishnamoorthy et al. (2018)

F and F mix

Congo Red Methyl red Reactive blue

95.2 6.2 90.4

Krishnamoorthy et al. (2018)

Type

Pseudomonas putida (MTCC1194) BF1, BF2

B and B mix

Pseudomonas beteli MRC 2-1 and Kosakonia cowanii CRC 1-1 Pseudomonas seleniipraecipitans MRC 4-1 and Kosakonia cowanii CRC 3-1 Klebsiella singaporensis CRC 1-1 and Kosakonia cowanii CRC 3-1 Dichotomomyces cejpii MRCH 1e2 and Phoma tropica MRCH 1-3 Dichotomomyces cejpii MRCH 1e2 and Fusarium solani MRCH 1e4

B and B mix

References

Continued

363

364

CHAPTER 16 Biodegradation of azo dye using microbiological consortium

Table 16.3 Microbiological consortia and dye decolorization.dcont’d Species used in the consortia Coriolus versicolor (MTCC 138), Phanerochaete chrysosporium (MTCC 787), Pleurotus ostreatus (MTCC 142) and Myrothecium verrucaria (MTCC 158)

Type F, F, F and F mix

Dye decolorized Cibacron yellow S-3R

Decolorization (%) 95

References Chitradevi and Sivakumar (2011)

B, Bacteria; F, Fungi.

4. Parameters involved during microbial azo-dye degradation The effective growth of these microbes and for the effective degradation of azo-dyes some of the important process parameters involved are carbon source, nitrogen source, dye concentration, inoculum size, pH, temperature, time, and method of agitation.

4.1 Effect of carbon source Any isolated bacterial strains can grow at an environment only when additional and abundant carbon sources is provided. Some of the carbon sources for bacterial strain Bacillus licheniformis such as glucose, sucrose, maltose, dextrose, cellulose, fructose, mannitol, and starch and the decolorization percentage is given in Fig. 16.3. Higher the carbon source, higher will be the decolorization percent (Gomaa, 2016). The dye effluents are deficient in carbon content and without any extra carbon sources is difficult for biodegradation. Glucose is an expensive carbon source for treatment of large volume of waste water, hence inexpensive carbon sources such as starch, molasses, and fructose are recommended for decolorization (Jamee and Siddique, 2019).

4.2 Effect of nitrogen source Nitrogen is responsible for growth and multiplication of microorganisms not only bacteria but also algae and fungi. Some of the nitrogen sources for the growth of Bacillus licheniformis are peptone, yeast extract, casein, urea, ammonium chloride, ammonium sulfate, ammonium nitrate, and sodium nitrate, and its effect of decolorization of Congo Red is shown in Fig. 16.3. It is clear that organic nitrogen sources like peptone and yeast extract were the best inducers for decolorization of Congo

Factors affecting decolorization of Congo Red using Bacillus licheniformis.

4. Parameters involved during microbial azo-dye degradation

FIGURE 16.3

365

366

CHAPTER 16 Biodegradation of azo dye using microbiological consortium

Red compared to the inorganic sources where these natural nitrogen sources induce metabolism of organisms for regeneration of NADH inside the cells, which is the electron donor for azo bond reduction (Gaur et al., 2015). The addition of urea into the solution a shifts the pH more toward acidic side, which increases the cell growth and enzyme activity; and decreases the color removal. The presence of nitrate in inorganic form slows down the decolorization process as it serves as electron acceptor thus no NADH regeneration is involved (Wainwright, 1999).

4.3 Effect of dye concentration It was observed from the decolorization of Congo Red using Bacillus licheniformis increased with increase in initial dye concentration from 50 to 200 mg/L and decreased beyond that at 250 mg/L. This reduction is due to the toxic effect of dye on the bacterial cells by inhibition of metabolic activity, dye products saturation in the cells, blockage of active site of azo-reductase enzymes by the dye molecules thereby inactivating the entire transport and regeneration system (Leelakriangsak and Borisut, 2012).

4.4 Effect of inoculum size It was observed from the decolorization of Congo Red using Bacillus licheniformis increased with increase in inoculum size from 5% to 20% (v/v) and decreased beyond that at 30% (v/v) as shown in Fig. 16.3. This varies from species to species and also the breathability of the dye bath as the solid cell concentration increases.

4.5 Effect of pH The pH of the medium is an important factor in dye decolorization, where the color removal is higher at the optimum pH and tends to decrease rapidly if medium becomes strongly acid or alkaline. This is purely related to the transport of dye molecules across the cell membrane and it is the rate limiting step for decolorization (Pandey et al., 2007). The maximum decolorization of Black B and CongoR using Bacillus subtili were observed at pH 7 (Gomaa, 2016). Bacillus sp. showed effective decolorization at 7e8 pH; but there are also few other bacteria which are efficient at one to four namely, Acinetobacter calcoaceticus, Pseudomonas aeruginosa strain BCH, Pseudomonas desmolyticum, and Stenotrophomonasmaltophilia (Mahmood et al., 2016). Some other studies gives yet another result especially for fungi mediated dye decolorization is effective at 4e6 pH and for a strain of Pseudomonas putida (MTCC1194) was efficient at 9e10.5 pH (Sen et al., 2016; Senan and Abraham, 2004).

4.6 Effect of temperature Temperature is the most critical parameter for dye decolorization as they are mainly enzymatic reactions. Thus there is a direct relationship observed between rate of

5. Conclusion

microbial growth and temperature in accordance to the enzymatic reactions. In most of cases growth increases with increase in temperature but it represses sharply and abruptly at extreme upper and lower limits of temperature. The higher temperature can attribute toward decline in decolorization due to the loss of cell viability and denaturation of the azo-reductase enzyme. In most of the cases the ambient temperature is between 26 and 30
C for separate and fungi consortia of Coriolus versicolor (MTCC 138), Phanerochaete chrysosporium (MTCC 787), Pleurotus ostreatus (MTCC 142), and Myrothecium verrucaria (MTCC 158); while for white rot fungi it was found to be around 25e37
C (Chitradevi and Sivakumar, 2011; Sen et al., 2016).

4.7 Effect of time The incubation period for dyes decolorization varies from hours to days with regards to one species to another. The maximum decolorization was recorded at 72 h for bacterial strains like Bacillus subtili, Bacillus cereu, Bacillus licheniformis, and Pseudomonas sp. and beyond, which there was no significant increase in decolorization (Gomaa, 2016). The fungi species Coriolus versicolor (MTCC 138), Phanerochaete chrysosporium (MTCC 787), Pleurotus ostreatus (MTCC 142), and Myrothecium verrucaria (MTCC 158) showed a maximum decolorization at 15 days (Chitradevi and Sivakumar, 2011).

4.8 Effect of agitation It was observed that under static conditions, the decolorization of azo dye, Congo Red tested was higher than under agitation as shown in Fig. 16.3. It was found out that under agitation conditions increases oxygen thereby depriving the azoreductase from obtaining electrons needed for cleavage of azo dyes under static conditions and these electrons are available to azo reductase from NADH to decolorize azo dyes (Tripathi et al., 2016). In case of biosorption based decolorization for Euchema Spinosum agitation is maintained up to 300 rpm for effective mixing (Mokhtar et al., 2017).

5. Conclusion This chapter highlights the use of azo dyes in textile industries, the types and the environmental concerns on dispersion of untreated dye effluent into the water bodies, with their adverse effects on the ecosystem. It also describes the different mechanism involved in azo-dye decolorization using microorganisms like bacteria, algae, fungi and the advantage of using microbiological consortia for effective treatment. The choice of the microorganism for the particular dye treatment and other important factors to be taken into consideration are given in detail.

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References Abid, M.F., Abdulahad Zablouk, M., Muhssen Abid-alameer, A., 2012. Experimental study of dye removal from industrial wastewater by membrane technologies of reverse osmosis and nanofiltration. Iran. J. Environ. Health Sci. Eng. 9, 1e9. Ajaz, M., Shakeel, S., Rehman, A., 2020. Microbial use for azo dye degradationda strategy for dye bioremediation. Int. Microbiol. 23 (2), 149e159. https://doi.org/10.1007/s10123019-00103-2. Benkhaya, S., M’rabet, S., El Harfi, A., 2020a. A review on classifications, recent synthesis and applications of textile dyes. Inorg. Chem. Commun. 115, 107891. https://doi.org/ 10.1016/j.inoche.2020.107891. Benkhaya, S., M’rabet, S., El Harfi, A., 2020b. Classifications, properties, recent synthesis and applications of azo dyes. Heliyon 6 (1). https://doi.org/10.1016/j.heliyon.2020.e03271. Cavicchioli, R., Ripple, W.J., Timmis, K.N., Azam, F., Bakken, L.R., Baylis, M., Behrenfeld, M.J., et al., 2019. Scientists’ warning to humanity: microorganisms and climate change. Nat. Rev. Microbiol. 17 (9), 569e586. https://doi.org/10.1038/s41579019-0222-5. Chan, G.F., Rashid, N.A., Koay, L.L., Chang, S.Y., Tan, W.L., 2011. Identification and optimization of novel NAR-1 bacterial consortium for the biodegradation of Orange II. Insight Biotechnol. 1 (1), 7e16. https://doi.org/10.5567/IBIOT-IK.2011.7.16. Chitradevi, V., Sivakumar, V., 2011. Optimization and kinetics evaluation of biodegradation of synthetic azo reactive dye by fungal consortium. J. Environ. Sci. Eng. 53 (4), 487e492. Corso, C.R., Maganha De Almeida, A.C., 2009. Bioremediation of dyes in textile effluents by Aspergillus oryzae. Microb. Ecol. 57 (2), 384e390. https://doi.org/10.1007/s00248-0089459-7. El-Ramady, Hassan, R., Alshaal, T.A., Amer, M., Domokos-Szabolcsy, E´., Elhawat, N., Prokisch, J., Fa´ri, M., 2014. Soil quality and plant nutrition. In: Ozier-Lafontaine, H., Lesueur-Jannoyer, M. (Eds.), Sustainable Agriculture Reviews 14: Agroecology and Global Change. Springer Switzerland, pp. 345e447. https://doi.org/10.1007/978-3-31906016-3_11. El-sheekh, Mostafa, M., Gharieb, M.M., Abou-El-Souod, G.W., 2009. International biodeterioration and biodegradation biodegradation of dyes by some green algae and cyanobacteria. Int. Biodeterior. Biodegrad. 63 (6), 699e704. https://doi.org/10.1016/ j.ibiod.2009.04.010. Gaur, R., Tiwari, S., Rai, P., Srivastava, V., 2015. Isolation, production, and characterization of thermotolerant xylanase from solvent tolerant Bacillus vallismortis RSPP-15. Int. J. Polym. Sci. 1e10. Gomaa, E.Z., 2016. Biodegradation and detoxification of azo dyes by some bacterial strains. Microbiol. J. 6 (1), 15e24. https://doi.org/10.3923/mj.2016.15.24. Jamee, R., Siddique, R., 2019. Biodegradation of synthetic dyes of textile effluent by microorganisms: an environmentally and economically sustainable approach. Eur. J. Microbiol. & Immunol. 9 (4), 114e118. https://doi.org/10.1556/1886.2019.00018. Jinqi, L., Houtian, L., 1992. Degradation of azo dyes by algae. Environ. Pollut. 75, 273e278. Krishnamoorthy, R., Jose, P.A., Ranjith, M., Anandham, R., Suganya, K., Prabhakaran, J., Thiyageshwari, S., Johnson, J., Gopal, N.O., Kumutha, K., 2018. Decolourisation and degradation of azo dyes by mixed fungal culture consisted of dichotomomyces cejpii MRCH 1-2 and phoma tropica MRCH 1-3. J. Environ. Chem. Eng. 6 (1), 588e595. https://doi.org/10.1016/j.jece.2017.12.035.

References

Kumar Gupta, V., 2020. Fundamentals of natural dyes and its application on textile substrates. Chem. & Technol. Nat. & Synth. Dyes & Pig. 1e32. https://doi.org/10.5772/ intechopen.89964. Leelakriangsak, M., Borisut, S., 2012. Characterization of the decolorizing activity of azo dyes by Bacillus subtilis azoreductase AzoR1. Songklanakarin J. Sci. Technol. 34 (5), 509e516. Madhav, S., Ahamad, A., Singh, P., Mishra, P.K., 2018. A review of textile industry: wet processing, environmental impacts, and effluent treatment methods. Environ. Qual. Manag. 27 (3), 31e41. https://doi.org/10.1002/tqem.21538. Mahalakshmi, S., Lakshmi, D., Menaga, U., 2015. Biodegradation of different concentration of dye (Congo red dye) by using green and blue green algae. Int. J. Environ. Res. 9 (2), 735e744. Mahmood, S., Khalid, A., Arshad, M., Mahmood, T., Crowley, D.E., 2016. Detoxification of azo dyes by bacterial oxidoreductase enzymes. Crit. Rev. Biotechnol. 36 (4), 639e651. https://doi.org/10.3109/07388551.2015.1004518. Mani, P., Fidal, V.T., Bowman, K., Breheny, M., Chandra, T.S., Keshavarz, T., Godfrey, K., September 2019. Degradation of azo dye (Acid orange 7) in a microbial fuel cell: comparison between anodic microbial-mediated reduction and cathodic laccase-mediated oxidation. Front. Energy Res. 7, 1e12. https://doi.org/10.3389/fenrg.2019.00101. Mansour, R., 2018. Natural dyes and pigments: extraction and applications. Handb. Renew. Mater. Color. & Finish. 75e102. https://doi.org/10.1002/9781119407850.ch5. Mishra, S., Kumar Nayak, J., Maiti, A., 2020. Bacteria-mediated bio-degradation of reactive azo dyes coupled with bio-energy generation from model wastewater. Clean Technol. Environ. Pol. 22 (3), 651e667. https://doi.org/10.1007/s10098-020-01809-y. Mokhtar, N., Aziz, E.A., Aris, A., Ishak, W.F.W., Saadiah, N., Ali, M., 2017. Biosorption of azo-dye using marine macro-alga of Euchema Spinosum. J. Environ. Chem. Eng. 5 (6), 5721e5731. https://doi.org/10.1016/j.jece.2017.10.043. Moody, V., Needles, H.L., 2004. 15 - color, dyes, dyeing, and printing. In: Moody, Von, Howard, L.B.T. (Eds.), Plastics Design Library, Tufted Carpet Needles. William Andrew Publishing, Norwich, NY, pp. 155e175. https://doi.org/10.1016/B978-1884207990.50016-6. Mothil, S., Chitra Devi, V., Senthilkumar, K., Raam, R.S., February 2019. Electro-coagulation of synthetic acid black 210 and acid red 1dye bath effluent using Fe and Al electrodes in a recirculation cell. Am. Int. J. Res. Sci., Technol. Eng. & Math. 138e143. http://www.iasir. net. Pandey, A., Singh, P., Iyengar, L., 2007. Bacterial decolorization and degradation of azo dyes. Int. Biodeterior. Biodegrad. 59 (2), 73e84. https://doi.org/10.1016/j.ibiod.2006.08.006. Petsas, A.S., Vagi, M.C., 2017. Effects on the photosynthetic activity of algae after review exposure to various organic and inorganic pollutants: review. In: Queiroz Zepka, L., Isabel Queiroz, M., Jacob-Lopes, E. (Eds.), Chlorophyll. IntechOpen, pp. 37e77. https://doi.org/ 10.5772/67991. Popli, S., Patel, U.D., 2015. Destruction of azo dyes by anaerobiceaerobic sequential biological treatment: a review. Int. J. Environ. Sci. Technol. 12 (1), 405e420. https://doi.org/ 10.1007/s13762-014-0499-x. Rawat, D., Mishra, V., Sharma, R.S., 2016. Detoxification of azo dyes in the context of environmental processes. Chemosphere 155, 591e605. https://doi.org/10.1016/ j.chemosphere.2016.04.068.

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Rekhate, C.V., Shrivastava, J.K., 2020. Decolorization of azo dye solution by ozone based advanced oxidation processes: optimization using response surface methodology and neural network. Ozone: Sci. Eng. 42 (6), 492e506. https://doi.org/10.1080/ 01919512.2020.1714426. Rowland, I., Gibson, G., Heinken, A., Scott, K., Swann, J., Thiele, I., Tuohy, K., 2018. Gut microbiota functions: metabolism of nutrients and other food components. Eur. J. Nutr. 57 (1), 0. https://doi.org/10.1007/s00394-017-1445-8. Samchetshabam, G., Hussan, A., Choudhury, T.G., 2017. Impact of textile dyes waste on aquatic environments and its treatment. Environ. Ecol. 35 (22), 2349e2353. Saratale, R.G., Saratale, G.D., Kalyani, D.C., Chang, J.S., Govindwar, S.P., 2009. Enhanced decolorization and biodegradation of textile azo dye scarlet R by using developed microbial consortium-GR. Bioresour. Technol. 100 (9), 2493e2500. https://doi.org/10.1016/ j.biortech.2008.12.013. Saxena, S., Raja, A.S.M., 2014. Natural dyes: sources, chemistry, application and sustainability issues. In: Muthu, S.S. (Ed.), Roadmap to Sustainable Textiles and Clothing. Springer, pp. 41e62. https://doi.org/10.1007/978-981-287-065-0_2. Sen, S.K., Raut, S., Bandyopadhyay, P., Raut, S., 2016. Fungal decolouration and degradation of azo dyes: a review. Fungal Biol. Rev. 30 (3), 112e133. https://doi.org/10.1016/ j.fbr.2016.06.003. Senan, R.C., Abraham, T.E., 2004. Bioremediation of textile azo dyes by aerobic bacterial consortium. Biodegradation 15 (4), 275e280. https://doi.org/10.1023/b:biod.0000043000. 18427.0a. Senthilkumar, K., Chitra Devi, V., Mothil, S., Naveen Kumar, M., 2018. Adsorption studies on treatment of textile wastewater using low-cost adsorbent. Desalin. & Water Treat. 123, 90e100. https://doi.org/10.5004/dwt.2018.22756. Singh, R.L., Singh, P.K., Pratap Singh, R., 2015. Enzymatic decolorization and degradation of azo dyes - a review. Int. Biodeterior. Biodegrad. 104, 21e31. https://doi.org/10.1016/ j.ibiod.2015.04.027. So´jka-Ledakowicz, J., Koprowski, T., Machnowski, W., Knudsen, H.H., 1998. Membrane filtration of textile dyehouse wastewater for technological water reuse. Desalination 119 (1), 1e9. https://doi.org/10.1016/S0011-9164(98)00078-2. Tripathi, A., Singh, Y., Verma, D.K., Rawat Ranjan, M., Srivastava, S.K., August 2016. Bioremediation of hazardous azo dye methyl red by a newly isolated Bacillus megaterium ITBHU01: process improvement through ANN-GA based synergistic approach. Indian J. Biochem. Biophys. 53, 112e125. Tyrone, L.V., 1994. Chapter 3 - methods of applying dyes to textiles. In: Textile Processing and Properties, vol. 11. Elsevier, pp. 112e192. https://doi.org/10.1016/B978-0-44488224-0.50008-4. Venkatachalam, C.D., Sengottian, M., Kandasamy, S., Balakrishnan, K., 2019. Biogenic synthesis of PdNCs embedded a-Fe2O3 microspheres using Myrtus cumini L. Leaf extract and a box-behnken optimization of its fenton-like catalytic activity. Glob. NEST: Int. J. 21 (3), 410e421. https://doi.org/10.30955/gnj.003133. Vingiani, G.M., De Luca, P., Ianora, A., Dobson, A.D.W., Lauritano, C., 2019. Microalgal enzymes with biotechnological applications. Mar. Drugs 17 (459), 1e20. Wainwright, M., 1999. Novel trends in biological waste water treatment. In: Wainwright, M. (Ed.), An Introduction to Environmental Biotechnology. Springer US, Boston, MA, pp. 85e94. https://doi.org/10.1007/978-1-4615-5251-2_8.

CHAPTER

Removal of pesticides from water and waste water by microbes

17

Pinal Bhatt, Anupama Shrivastav Department of Microbiology, Parul Institute of Applied Sciences, Parul University, Vadodara, Gujarat, India

1. Introduction From the end of the 20th century to the present, the total global grain output has increased from 500 million tons to 700 million tons now (http://www.fao.org/ faostat/en/#data/QC 2018). Among them, cereals account for 80% of human consumption of food (Sola` et al., 2018). Food is effected by insects and microorganisms, which are called pests during its natural growth or storage. Present agriculture is readily related through the utilization of diverse chemical contribution. Alternative classes of pesticides are used in managing dissimilar grouping of pests to make the most of crop production and congregate the demands for higher provisions of food of the fast-growing human population. During the 16th and 17th centuries, Japanese mixed poor-quality whale oil with vinegar for spraying on rice paddies to prevent the development of insect larvae and water extracts of tobacco leaves were sprayed on plants to kill insects (Ahmad et al., 2010). The Nux Vomica, the seed of Strychoros nuxmonica (Strychnine), was employed to kill rodents. In the beginning of 19th century, insecticides isolated from plants included rotenone from the root of Derris eliptica and pyrethrum extract from flowers of chrysanthemums; arsenic trioxide was used as a weed killer, copper arsenite was used for the control of Colorado beetle, Bordeaux mixture (copper sulfate, lime and water) was applied to combat vine downy mildew. The modern era of chemical pest control began around the time of World War II, when the synthetic organic chemical industry began to develop (Ahmad et al., 2010). The first synthetic organic pesticides were organochlorine compounds, such as dichlorodiphenyltrichloroethane (DDT), whose commercial production began in 1943. During the mid-1940s the production and use of synthetic organic pesticides rapidly increased. Today, more than 500 different formulations of pesticides are being used in the environment, and agriculture holds the largest single share of pesticides use (Ahmad et al., 2010). An idyllic pesticide has to be poisonous only to the target organism, recyclable, and should not percolate into ground water. Unfortunately, this is hardly ever the case and the extensive use of pesticides in recent agriculture is of concern Development in Wastewater Treatment Research and Processes. https://doi.org/10.1016/B978-0-323-85657-7.00016-X Copyright © 2022 Elsevier Inc. All rights reserved.

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(Krishnasamy et al., 2019). Due to the incessant use of pesticides in agriculture, considerable amount of herbicides and their tainted products may build up in the ecosystem leading to serious trouble to man and the surroundings (Krishnasamy et al., 2019). Consequently, it is necessary to learn the residue and deprivation pattern of herbicides in crops, soils and water scientifically in order to create significant information from the point of view of plant fortification, public health and ecological protection. The dilapidation of herbicides in soil and their cause on microbes should be studied so that their use can be appropriately synchronized (Krishnasamy et al., 2019). The rapidly growing industrialization along with an increasing population has resulted in the accumulation of a wide variety of chemicals. Thus, the frequency and widespread use of artificial “xenobiotic” chemicals has led to a remarkable effort to implement new technologies to reduce or eliminate these contaminants from the environment. Commonly used techniques of waste treatment (e.g., landfilling, recycling, pyrolysis, and incineration) have also had detrimental effects on the environment, contributing to the creation of toxic chemical intermediates for the remediation of polluted areas (Jain et al., 2005). Furthermore, these methods are more expensive and sometimes difficult to execute, especially in extensive agricultural areas, as for instance pesticides (Jain et al., 2005). The use of pesticides is ubiquitous in modern agriculture and is important to increase crop yield and reduce postharvest losses. However, indiscriminate and excessive use of agricultural pesticides can lead to contamination of land and water (Hai et al., 2012). Emissions of pesticides come from both diffuse and point sources. The latter include mixing and loading facilities on the farm where spillages and leakages from the filling operation and spray equipment, and water from rinsing and cleaning of the equipment may contribute to pesticide contamination (Hai et al., 2012). Wastewater generated in vegetable washing facilities and pesticide manufacturing plants are also important point sources of pollution (Hai et al., 2012). Much research of pesticide hazards are generally attributed to aspects such as the useful biological effect was destroyed and the control effect was weakened. Pesticide residues have risen in agricultural and secondary products, placing human health at risk. Increased resistance to pests, increased cost of prevention and treatment, increased contamination of the atmosphere and also the soil, atmosphere and water pollution have badly damaged our living environment (Xiaolan et al., 2018a,b).

2. Pesticide Pesticides are distinguished by their particular chemical structure or patterns of use by society and their contact with the environment. In targeted biological reactions, pesticide structures are formed to imitate and thus substitute for specific molecules (Ahmad et al., 2010). In agriculture or in public health protection, pesticides are used to protect plants from rodents, weeds or diseases and humans from vector-borne diseases such as

2. Pesticide

malaria, dengue fever and schistosomiasis. Insecticides, fungicides, herbicides, rodenticides, and plant growth regulators are typical examples (NicolopoulouStamati et al., 2016). These chemicals are also used to develop and preserve nonagricultural areas, such as public urban green areas and sports fields, for other purposes (Nicolopoulou-Stamati et al., 2016). They can primarily be categorized by taking two factors into account: chemical groups and the target organism. Different exposure paths, such as inhalation, ingestion, and dermal contact, expose humans to pesticides (Ahmad et al., 2010). The term “pesticide” is a contraction used to define a variety of agents that are classified on the basis of their potential to kill living organisms. There are various types of pesticide: insecticides, herbicides, and fungicides. Pesticides are created to control certain living organisms so they are biologically active and they are sources of exposure for much of the human population because of their pervasive presence in the living and working environment (Ahmad et al., 2010). Such exposure creates concern. These compounds vary from all other chemical substances in that they are intentionally transmitted to the atmosphere and are consequently marked by variable levels of toxicity because they are meant to interact with certain living organisms (Ahmad et al., 2010; Corsini et al., 2008). From Table 17.1 we can see the different types of pesticides used in agriculture.

Table 17.1 Different types of pesticides used in agriculture practices (Huang et al., 2018). Name of pesticide

Category

Used as

References

Benzoylphenyl Ureas, chlordimeform. Acephate, azinphos-methyl, bromophos, chlorpyrifos, coumaphos, diazinon, dimethoate, dioxathion, disulfoton, diazinon, ectophos, fenitrothion, fenitrooxon, fonofos, glyphosate, leptophos, malathion, mathamidophos, parathion, phenthoate, profenofos, phorate, phosmet, phosphothion, trichloffon, trichlorfon Aldrin, chlordane, DDT, dieldrin, dicofol, endosulfan, endrin, fipronil, heptachlor, lindane, BHC, hexachlorocyclohexane

Organic nitrogen Organic phosphorus

Insecticide

Huang et al. (2018)

Insecticide

Chowdhury et al. (2013), Bhandari (2017), Ye et al. (2018), Liu et al., (2013). Huang et al. (2018)

Organic chlorine

Insecticide

Ye et al. (2018), Bhandari (2017), Chowdhury et al. (2013), Huang et al. (2018). Continued

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Table 17.1 Different types of pesticides used in agriculture practices (Huang et al., 2018).dcont’d Name of pesticide

Category

Used as

References

Aldicarb, carbaryl, carbofuran, carbosulfan, cartap

Carbamate

Insecticide

Cypermethrin, chlorfenvinphos, deltamethrin, fenvalerate, flumethrin, permethrin, ivermectin Azadirachtin, benzoylphenylurea, diflubenzuron, methoxyfenozide, pyriproxyfen, spinosad, tebufenozide Amitraz, coumaphos, dimethoatet, fenpyroximate, formic acid, menthol, taufluvalinate, thymol Acetanilides, alachlor, barban, chlorbromuron, hlorophenoxy, dalapon, diuron, glyphosate, linuron, monuron, neburon, pendimethalin, pentachlorophenol, propham, salted iron phosphorus, swep, 2,4-D, 2,4,5-T Bayleton, blue copper, chlorothalonil, copper hydrochloride, copper oxychloride, copper sulfate, different rice blast net, dithane, dithiocarbamates, mancozeb, metalaxyl, methyl phosphorus, impact, polytrin, ridomil, rice blast net, triazoles, thiocarbamates, thiovit

Pyrethroid

Insecticide

Chowdhury et al. (2013), Huang et al. (2018). Chowdhury et al. (2013). Huang et al. (2018)

Insect growth regulators

Insecticide

Huang et al. (2018)

Acaricides

Ye et al. (2018), Huang et al. (2018)

Herbicide

Hai et al. (2012), Tang (2018), Liu et al. (2013), Huang et al. (2018)

Bactericide

Tang (2018), Huang et al. (2018).

2.1 Organochloride pesticide Dichlorodiphenyltrichloroethane, i.e., the insecticide DDT, has been the most commonly known organochlorine pesticide, the unregulated use of which raised many health and environmental problems. Some additional organochlorines used as pesticides are Dieldrin, endosulfan, heptachlor, dicofol, and methoxychlor. There are a few countries that still use DDT or plan to reintroduce it for public health purposes (Nicolopoulou-Stamati et al., 2016).

3. Impact of pesticide

2.2 Organophosphate pesticide Organophosphates, which were promoted as a more ecological alternative to organochlorines (Nicolopoulou-Stamati et al., 2016), include a great variety of pesticides, the most common of which is glyphosate. This class also includes other known pesticides, such as malathion, parathion, and dimethoate; some are known for their endocrine-disrupting potential (Gasnier et al., 2009). This class of pesticides has been associated with effects on the function of cholinesterase enzymes (Nicolopoulou-Stamati et al., 2016), decrease in insulin secretion, disruption of normal cellular metabolism of proteins, carbohydrates and fats (Karami-Mohajeri and Abdollahi, 2011), and also with genotoxic effects (Nicolopoulou-Stamati et al., 2016) and effects on mitochondrial function, causing cellular oxidative stress and problems to the nervous and endocrine systems (Karami-Mohajeri and Abdollahi, 2011; Nicolopoulou-Stamati et al., 2016).

2.3 Carbamate pesticide Carbamate pesticides are another type of chemical pesticides associated with endocrinedisrupting activity, such as aldicarb, carbofuran, and ziram (Nicolopoulou-Stamati et al., 2016), possible reproductive disorders (Nicolopoulou-Stamati et al., 2016), and effects on cellular metabolic mechanisms and mitochondrial function (Karami-Mohajeri and Abdollahi, 2011; Nicolopoulou-Stamati et al., 2016).

2.4 Other classes Another class of chemical pesticides associated with endocrine-disrupting effects and reproductive toxicity are triazines, such as atrazine, simazine, and ametryn (Jin et al., 2014). Moreover, it was found that there is a possible statistical relationship between triazine herbicides and breast cancer incidence (Nicolopoulou-Stamati et al., 2016). Atrazine is the most known of the triazines, and it is a very widely used herbicide that has been associated with oxidative stress (Jin et al., 2014), cytotoxicity (Huang et al., 2014), and dopaminergic effects (Nicolopoulou-Stamati et al., 2016).

3. Impact of pesticide Many of the pesticides have been associated with health and environmental issues and because of that the agricultural use of certain pesticides has been abandoned (Nicolopoulou-Stamati et al., 2016). Exposure of pesticides can be in many ways: through contact with the skin, ingestion, or inhalation. The numerous negative health effects that have been associated with chemical pesticides include, among other effects, dermatological, gastrointestinal, neurological, carcinogenic, respiratory, reproductive, and endocrine effects (Nicolopoulou-Stamati et al., 2016) and high occupational, accidental, or intentional exposure to pesticides can result in hospitalization and death (Nicolopoulou-Stamati et al., 2016).The pesticide form, exposure

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period and route of exposure, and individual health status (e.g., nutritional deficiencies and healthy/damaged skin) are the determinants of the potential health outcome. Within a human or animal body, pesticides may be metabolized, excreted, stored, or bioaccumulated in body fat (Nicolopoulou-Stamati et al., 2016). The general class of organochlorine pesticides has been correlated with health effects, such as endocrine disorders, embryonic development effects, lipid metabolism (Karami-Mohajeri and Abdollahi, 2011; Nicolopoulou-Stamati et al., 2016) and hematological and hepatic alterations. DDT is a widespread organic material, and it is known that every living creature on Earth has a body burden of DDT, often contained in fat (Nicolopoulou-Stamati et al., 2016). In addition, DDT is often used as a solution in some solvents (Nicolopoulou-Stamati et al., 2016). Also there is proof that DDT and its metabolite p, p dichlorodiphenyldichloroethylene (DDE) may have endocrine-disrupting capacity and carcinogenic impact (NicolopoulouStamati et al., 2016). Neurodevelopmental symptoms in infants have been associated with utero exposure to both DDT and DDE (Nicolopoulou-Stamati et al., 2016). Population-based studies have revealed possible relations between the exposure to organophosphorus pesticides and serious health effects including cardiovascular diseases (Hung et al., 2015; Ahmad et al., 2010), negative effects on the male reproductive system (Nicolopoulou-Stamati et al., 2016) and on the nervous system (Nicolopoulou-Stamati et al., 2016), dementia (Lin et al., 2015), and also a possible increased risk for non-Hodgkin’s lymphoma (Nicolopoulou-Stamati et al., 2016). Furthermore, prenatal exposure to organophosphates has been correlated with decreased gestational duration (Nicolopoulou-Stamati et al., 2016) and neurological problems occurring in children (Rauh et al., 2015; Nicolopoulou-Stamati et al., 2016). Several in vitro studies have revealed the ability of carbamate pesticides to cause cytotoxic and genotoxic effects in hamster ovarian cells (Soloneski et al., 2015; Nicolopoulou-Stamati et al., 2016) and to induce apoptosis and necrosis in human immune cells (Li et al., 2011), natural killer cells (Li et al., 2014), and also apoptosis in T lymphocytes (Li et al., 2015). As per the studies, it has been confirmed that carbaryl falls under carbamate pesticides category, can act as a ligand for the hepatic aryl hydrocarbon receptor, a transcription factor involved in the mechanism of dioxin toxicity (Nicolopoulou-Stamati et al., 2016). There is also evidence for the ability of carbamate pesticides to cause neurobehavioral effects (NicolopoulouStamati et al., 2016), increased risk for dementia (Lin et al., 2015), and nonHodgkin’s lymphoma (Nicolopoulou-Stamati et al., 2016). Furthermore, the exposure of experimental animals to atrazine has been associated with reproductive toxicity (Song et al., 2014) and delays in sexual maturation (Breckenridge et al., 2015; Nicolopoulou-Stamati et al., 2016). Among the safer insecticides currently available for agricultural and public health purposes, synthetic pyrethroids such as fenvalerate, permethrin, and sumithrin are considered to be (Ahmad et al., 2010). However, there is evidence for their ability to display endocrine-disrupting activity (Ahmad et al., 2010), and to affect reproductive parameters in experimental animals, including reproductive behavior (Ahmad et al., 2010).

3. Impact of pesticide

Pesticide pollution to the local environment also affects the lives of birds, wildlife, domestic animals, fish, and livestock (Ahmad et al., 2010). The general population is exposed to the residues of pesticides, including physical and biological degradation products in air, water, and food (Ahmad et al., 2010). Increasingly, acute exposure to pesticides were illustrated as vulnerable to a wide spectrum of immunosuppression (favorably among low-income populations, malnutrition, and unsanitary conditions), neurobehavioral disorders and developmental toxicity presage as allergy, autoimmune disease, reproductive abnormalities (spermatogenetic dysfunction, mal-descent of testes, and malformations of penis) (Ahmad et al., 2010), multiple myeloma, leukemia, malignant lymphoma, increased kit mortality, deformities, life-threatening bleeding and myocytes with burning sensation in the mouth and throat, nausea, vomiting, sweating, hyperventilation, pain, fasciculation, myotonia, weakness, and myoglobinuria (Corsini et al., 2008; Foo and Hameed, 2010). Pesticide pollution to the local environment also affects the lives of birds, wildlife, domestic animals, fish, and livestock. The general population is exposed to the residues of pesticides, including physical and biological degradation products in air, water, and food. Genotoxic potential is a primary risk factor for long-term effects such as carcinogenic and reproductive toxicology. The majority of pesticides have been tested in a wide variety of mutagenicity assays covering gene mutation, Removal of Pesticides from Water and Wastewater 233 chromosomal alteration, and DNA damage. Pesticides have been considered potential chemical mutagens (Ahmad et al., 2010). In the majority of cases, the concentrations do not exceed the legislatively determined safe levels (Nicolopoulou-Stamati et al., 2016). However, these “safe limits” may underestimate the real health risk as in the case of simultaneous exposure to two or more chemical substances, which occurs in real-life conditions and may have synergistic effects (Nicolopoulou-Stamati et al., 2016). Pesticides residues have also been detected in human breast milk samples, and there are concerns about prenatal exposure and health effects in children (Nicolopoulou-Stamati et al., 2016). The use of unprescribed pesticides in inappropriate doses is not only disturbing the soil conditions but also destroying the healthy pool of biocontrol agents that normally coexist with the vegetation (Ahmad et al., 2010). Throughout history, various types of pests, such as insects, weeds, bacteria, rodents, and other biological organisms, have affected or threatened human health because of their use for thousands of years to control the pests. The early concept regarding pesticide practice was using sulfur as fumigant, which was initiated by Chinese during the 1000 B.C. in Samaria (Ahmad et al., 2010). The Chinese also used mercury and arsenic compounds to control body lice and other pests. Oil, ash, sulfur, and other materials were used by the Greeks and Romans to defend themselves, their animals, and their crops from various pests. In addition people in various cultures have used smoke, salt, spices, and insect-repelling plants to preserve food and keep pests away (Ahmad et al., 2010).

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4. Metabolism and degradation of pesticide 4.1 Application of adsorbent 4.1.1 Carbonaceous adsorbents A wide variety of carbons have been prepared from biomass and other wastes, such as date stone, wood (Sudhakar and Dikshit, 2008), biochar (Cao et al., 2009), coconut shell, coconut fibers, bagasse, sal wood, green waste (Zheng et al., 2010), peat moss, horseshoe sea crab shell (Ahmad et al., 2010), corn stillage, and oil palm fronds (Salman and Hameed, 2010). The use of byproducts or residues of agricultural wastes as precursors for the production of cheap and effective activated carbon adsorbents has been reported in the literature (Ahmad et al., 2010). In recent years, many researchers have tried to produce activated carbons for removal of various pollutants using renewable and cheaper precursors, which were mainly industrial and agricultural byproducts (Ahmad et al., 2010). Adsorption process is a surface phenomenon that depends on the number of sites available, porosity, and specific surface area of adsorbent as well as various types of interactions (Ahmad et al., 2010). Generally, carbonaceous materials have a special place among the main adsorbents, as they are known, for a long time to be capable of adsorbing various organic compounds. Activated carbon due to its high surface area and porosity is very efficient in removing different varieties of pesticides from water and wastewater (Ahmad et al., 2010). It is a versatile material that can be applied in many technological processes. A number of activated carbon materials, such as granular activated carbon (GAC), powdered activated carbon (PAC), carbon cloth, carbon fibers, black carbon, activated carbon composites (Castro et al., 2009), and commercial activated carbon (CAC) have been used (Ahmad et al., 2010). The forms GAC and PAC are the most used since they are considered very capable and effective materials for the adsorption of a variety of pesticides (Ahmad et al., 2010).

4.1.2 Agricultural wastes adsorbents Activated carbon has been a popular choice as an adsorbent for the removal of pesticides from wastewater, but its high cost poses an economical problem (Ahmad et al., 2010). Therefore, researchers felt the necessity for the event of low cost and simply available materials, which may be used more economically on an outsized scale. It opened the doors of research interests into the production of alternative adsorbents to replace the costly activated carbon that has intensified in recent years (Ahmad et al., 2010). The waste materials and byproducts from the agriculture and other industries are the sources of low-cost adsorbents thanks to their abundance in nature and since they need processing requirements. In recent years, a new class of adsorbents and specifically lignocellulosic materials has been investigated for the same purposes: their attractiveness resulting from their availability, low cost, and biodegradability (Ahmad et al., 2010). Some previous studies reported their ability to quantitatively accumulate heavy metals and various organic compounds such as dyes and pesticides. Accumulation of these pesticides on agricultural adsorbents is generally achieved through interactions with the hydroxyl and carboxyl groups

4. Metabolism and degradation of pesticide

particularly abundant in polysaccharides (cellulose and hemicelluloses) and lignin, both of which constitute about 90% of dry lignocellulosic materials. Several recent publications reported the use of low-cost and locally available adsorbents, e.g., Ayous sawdust (Nanseu-Njiki et al., 2010), rice husk, date stones (El Bakouri et al., 2009), watermelon peels, rice bran (Akhtar et al., 2009), pine sawdust, oak sawdust, tea leaves (Islam et al., 2009), wood sawdust (Islam et al., 2009), chestnut shells, bamboo canes, straw, mango kernel (Memon et al., 2009), peanut shells, and peach nut shells. Akhtar et al. (2009) reported in their work that low-cost agricultural waste (i.e., rice bran and rice husk) are often effectively wont to remove triazophos pesticide from water (Ahmad et al., 2010).

4.1.3 Polymeric adsorbents Due to high cost of regeneration of the mechanically fragile activated carbons, alternative sorbents such as polymeric resins have been synthesized as potential alternatives to activated carbons. Macroporous (macroreticular) (co-)polymers of nonionic polymeric resins are frequently used in water treatment (Ahmad et al., 2010). More recently, hyper cross-linked polymeric adsorbents have been developed that possess widespread applicability because of their large area and special functional groups tagged to a matrix of polymeric chains. Hyper cross-linked resins are widely used in industries as well as analytical scales (Ahmad et al., 2010). Several reports revealed that hypercross-linked polymers have high potential for the adsorption of organic and inorganic compounds, storage of hydrogen, etc. (Ahmad et al., 2010), interpreting that they were successfully applied in the removal of both organic and inorganic compounds with their unique physical structures. The use of polymeric adsorbents to remove organic compounds from aqueous solutions, to purify process streams, and to recover valuable compounds from aqueous solutions has been investigated (Ahmad et al., 2010). So far, research work on adsorption on polymeric resins for the separation of pesticides from aqueous systems is extremely limited (Aouada et al., 2009). A category of polymeric resins that has been widely investigated for the removal of organic compounds, pharmaceuticals, and pesticides from aqueous solutions is amberlite adsorbents (Ahmad et al., 2010). (Biomimetic fat cell - BFC)dsynthesized by interfacial polymerization for the removal of lindane. The synthesized BFC has a hydrophobic nucleolus-triolein and hydrophilic membrane structure polyamide, from which the water carrying the HOCs can pass into the interior, followed by the accumulation of the HOCs (Ahmad et al., 2010). Lindane removal by BFC may occur through two mechanisms: bioaccumulation by BFC nucleolus-triolein and adsorption by BFC membrane (Ahmad et al., 2010). Lindane removal efficiency of BFC decreased as regeneration time increased. BFC was enhanced by the incorporation of 1,3,5-benzenetricarboxyl trichloride with trifunctional group and heterocyclic piperazine to boost the regeneration potential of BFC for the removal of lindane. The lindane removal mechanism by MBFC, similar to BFC, includes bioaccumulation by MBFC nucleolus-triolein and adsorption by MBFC membrane; bioaccumulation is the main way (Ahmad et al., 2010).

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4.1.4 Industrial wastes adsorbents Development of low-cost adsorbents for pesticide retention is an important area of research in environmental sciences. Industrial wastes such as sludge, fly ash, and carbon slurry are classified as low-cost materials because of their low cost and local availability and can be used as adsorbents for pesticides removal. The fly ash, a solid waste from lignite coal-fired thermal power stations, is a low-cost adsorbent and has shown significant adsorption capacity for organic pollutants (Ahmad et al., 2010). Few reports have highlighted the pesticide sorption potential of fly ash (Singh, 2009) and have recommended it for use in the removal of pesticides from water and wastewater samples (Sharma et al., 2008). Singh (2009) reported that coal fly ash has significantly high retention capacity for metribuzin, metolachlor, and atrazine. Atrazine was the maximum absorbed followed by metolachlor and metribuzin (Ahmad et al., 2010). The herbicide sorption efficiency of fly ash depended on the initial concentration of herbicide in the solution, and maximum removal of herbicide was observed at lower concentrations, which is generally encountered in the water samples. The study recommended that fly ash be exploited as a low-cost adsorbent for chosen pesticides from wastewater and runoff water from agricultural soils (Ahmad et al., 2010).

4.1.5 Bioadsorbents Biosorption is used to denote a variety of processes independent of metabolism (physical and chemical adsorption, electrostatic activity, ion exchange, complexation, chelation, and microprecipitation) that exist mainly in the cell wall instead of anaerobic or aerobic metabolism (biodegradation) oxidation (Ahmad et al., 2010). The main attractions of biosorption are high selectivity and efficiency, cost effectiveness, and good removal performance. Raw materials, which are either abundant (sea weeds) or wastes from other industrial operations (fermentation wastes, activated sludge process wastes), can be used as biosorbents presenting performances often comparable with those of ion exchange resins (Ahmad et al., 2010). Both living and dead (heat killed, dried, acid, and/or otherwise chemically treated) biomass can be used to remove pesticides, but maintaining a viable biomass during adsorption is difficult because it requires a continuous supply of nutrients and avoidance of organic toxicity to the microorganisms (Ahmad et al., 2010). The use of dead microbial cells in biosorption is more advantageous for water treatment because dead organisms are not affected by toxic wastes, they do not require a continuous supply of nutrients, and they can be regenerated and reused for many cycles (Ahmad et al., 2010). Dead cells may be stored or used for extended periods at room temperature without putrefaction. Their operation is easy and their regeneration is simple. Moreover, dead cells have been shown to accumulate pollutants to the same or greater extent of growing or resting cells (Ahmad et al., 2010). Inactivated biomass binding mechanisms can rely on the chemical structure of the pollutant (species, scale, and ionic charge), the form of biomass, and the preparation thereof. And its specific surface properties, and environmental conditions (pH, temperature, ionic strength, existence of competing organic or inorganic ligands

4. Metabolism and degradation of pesticide

in solution) (2005). In recent years the ability of microorganisms to metabolize some pesticides has also received much attention due to the environmental persistence and toxicity of these chemicals. Although in some cases, microbial metabolism of contaminants may produce toxic metabolites, a variety of microorganisms (many aerobic bacteria and fungi) are known to utilize organic pesticides as the sole carbon or energy source, such as Pseudomonas pickettii, Alcalilgenes eutrophus, Desulfomonile tiedjei, Phanerochaete chrysosporium, and so on (Ahmad et al., 2010). However, conventional activated sludge systems often fail to achieve high efficiency in removing pesticides from wastewater due to the low biodegradability and toxicity or inhibition of organic pesticides to microorganisms. Application of biosorption for pesticides is also possible, and several microorganisms including bacteria and fungi have been studied for the removal of some pesticides. Researcher, investigated the adsorption behavior of lindane on Rhizopus oryzae biomass (Ahmad et al., 2010). They found that the adsorption process does not depend on the pH of the solution or incubation temperature. Hydrophobic interaction is mainly responsible for this adsorption process (Ahmad et al., 2010). It can be used for the adsorptive removal of lindane from wastewater containing different matrices. Chatterjee et al. (2010), studied the interaction of malathion, an organophosphorus pesticide with Rhizopus oryzae biomass. They found that the amine groups of chitosan are mainly responsible for chemical interaction between malathion and Rhizopus oryzae cell wall (Ahmad et al., 2010). Hydrophobic interaction is the main cause of physical interaction as adsorption of malathion decreased to a great extent after removing lipids from Rhizopus oryzae biomass. It may be used for the removal of malathion from potable water. Extraction of lipids from biomass decreases its adsorption capacity to the extent of 36.37%e94.02%, depending on the polarity of the solvent (Ahmad et al., 2010). Bell and Tsezos (1987), reported on the biosorption of pentachlorophenol (PCP) onto two types of inactive microbial biomass: a mixed culture of aerobic activated sludge and a pure culture of Rhizopus arrhizus (Ahmad et al., 2010). Based on the examination of the uptake by cell walls, they concluded that biosorption process involves uptake by both the cell walls and other cellular components of the microorganisms. They reported that dead cells of Rhizopus arrhizus had a higher biosorption capacity for PCP than that of dead activated sludge (Ahmad et al., 2010).

4.1.6 Inorganic adsorbents From the early days of civilization, natural clay minerals have been well known and common to mankind. Because of their low cost, abundance in most continents of the world, high sorption properties, and potential for ion exchange, clay materials are strong adsorbents (Ahmad et al., 2010). They possess layered structure and are considered as host materials for the adsorbates and counter ions (Ahmad et al., 2010). In recent years, the use of clay minerals such as cloisite, clinoptilolite, eluthrilite, kerolite, faujasite, montmorillonite, and palygorskite for their ability to adsorb not only inorganic ions but also organic molecules has become increasingly significant. More recently, low-cost adsorbents, for example, organoclay complex

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adsorbents, have been investigated as an alternative to activated carbon (Ahmad et al., 2010). These materials, often used in industrial and technological processes, have been proposed as adsorbents for the immobilization of industrial organic contaminants (Suciua and Capri, 2009), for the removal of pesticides from water (Ahmad et al., 2010), for the development of slow-release pesticide formulations (Ahmad et al., 2010), or for the examination of bioavailability potential (Ahmad et al., 2010) and photostabilization of sorbed pesticides (Ahmad et al., 2010). The summary of these research works on the removal of different pesticides is given in Table 17.2. Suciua and Capri (2009) reported the efficiency of different clays and modified clays in removing pesticide residues at concentrations that mimic the contamination level of wastewater at the farmyard level (Ahmad et al., 2010). The adsorption of the three pesticides onto the two micelle-clay complexes and unmodified montmorillonite clay was measured to allow the determination of the maximum pesticide quantity adsorbed in order to obtain a dose-effect relationship for practical applications (Ahmad et al., 2010).

4.1.7 Miscellaneous adsorbents Various other materials have also been put to use for preparing alternative adsorbents. Since their discovery by Ahmad et al. (2010), carbon nanotubes (CNTs) have attracted great interest because of their unique chemical structure and intriguing physical properties. They have been investigated for use as adsorbents due to their high surface area and unique structure. It has been found that CNTs are more effective for the removal of dioxin than activated carbon because of strong interaction between dioxin and carbon nanotubes (Ahmad et al., 2010). Depending on the layers involved, carbon nanotubes (CNTs) have been referred as single-walled (SWCNTs) or multi-walled carbon nanotubes (MWCNTs) (Ahmad et al., 2010). CNTs have been considered useful in pollution prevention strategies and are known to have widespread applications as environmental adsorbents and high-flux membranes (Ahmad et al., 2010) and are also potentially important for in situ environmentalremediation due to their unique properties and high reactivity (Ahmad et al., 2010). Investigations dealing with the sorption of organic contaminants, such as dioxin (Ahmad et al., 2010), 1,2-dichlorobenzene (Ahmad et al., 2010), polycyclic aromatic hydrocarbons (PAHs) (Ahmad et al., 2010), and o-xylene, p-xylene (Ahmad et al., 2010), and reactive dyes (Ahmad et al., 2010) on CNTs suggest that they may also be suitable materials for the preconcentration and solidification of pollutants from large volumes of wastewater (Ahmad et al., 2010).

5. Biodegradation Biodegradation studies began in the 1940s, and it was initially thought that biodegradation refers to the destruction or mineralization of aerobic microbes in the soil, water and wastewater biological treatment systems for natural and synthetic organic

Table 17.2 Pesticide-degrading common microorganisms (Huang et al., 2018): Pesticides Aldrin, chlorpyrifos, coumaphos, ddt, diazinon, endosulfan, endrin, hexachlorocyclohexane, methyl parathion, monocrotophos, parathion. Chlorpyrifos, coumaphos, DDT, diazinon, dieldrin, endosulfan, endrin, glyphosate, methyl parathion, monocrotophos, parathion, polycyclic aromatic hydrocarbons Chlorpyrifos, endosulfan, Diazinon, glyphosate, methyl parathion, parathion Aldrin, carbofuran, chlorpyrifos, diazinon, diuron

Type of microorganisms

Pseudomonas

Bacteria

References Verma et al. (2014), Upadhyay and Dutt (2017).

Bacillus

Verma et al. (2014), Upadhyay and Dutt (2017).

Alcaligenes Flavobacterium

Verma et al. (2014), Upadhyay and Dutt (2017), Kafilzadeh et al. (2015). Verma et al. (2014) Jayabarath et al. (2010), Bricen˜o et al. (2017). Hai et al. (2012), Elgueta et al. (2016), Upadhyay and Dutt (2017), Sagar and Singh (2011), Bhandari (2017), RomeroAguilar et al. (2014), Kataoka et al. (2010), Birolli et al. (2016), Wolfand et al. (2016), Xiao et al. (2012).

Micromonospora, Actinomyces, Nocardia, Streptomyces White-rot fungi, Rhizopus, Cladosporium, Aspergillus fumigatus, Penicillium, Aspergillus, Fusarium, Mucor, Trichoderma spp, Mortierella sp. Small green algae Chlamydomonas Genus of diatoms

Actinomycetes

Fungus

Algae

Tang (2018), Kabra et al. (2014).

5. Biodegradation

Alachlor, aldicarb, atrazine, carbofuran, chlordane, chlorpyrifos, DDT, diuron, endosulfan, esfenvalerate, fenitrothion, fenitrooxon, fipronil, heptachlor epoxide, lindane, malathion metalaxyl, pentachlorophenol, terbuthylazine, 2,4D Phorate, parathion Atrazine, fenvalerate DDT, patoran

Name of degrading Microorganisms(Species)

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matter (Xiaolan et al., 2018a,b). Since the role of microorganisms in the various biodegradation is greatest, it is generally mentioned that biodegradation mainly refers to microbial degradation (Xiaolan et al., 2018a,b). On the current level of technology, chemical pesticides in the future for a long time or irreplaceable products. Therefore, the solution of pesticide residues in the environment has become a hot topic in the world. Among them, the microbial repair is universally recognized as a safe and effective method of remediation of soil pollution (Huang et al., 2011; Xiaolan et al., 2018a,b).

5.1 Types of pesticides-degrading microorganism In recent years, lot of microbial floras, such as bacteria, fungi, actinomycetes, algae and other microbial strains have enriched, isolated, cultured and screened from the natural sewage or soil by many scientists to degrade pesticides (Huang et al., 2018). Kafilzadeh et al. (2015) separated bacteria from sediments and water samples from high agricultural activity areas for the detection of endosulfan degradation. Endosulfan could be degraded very efficiently by the five bacteria genus klebsiella, acinetobacter, alcaligenes, flavobacterium, and bacillus. Jayabarath et al. (2010) selected 319 actinomycetes from saline soils of Sangli District (Maharashtra) for carbofuran tolerance test, while only the seven strains of Streptomyces alanosinicus, Streptoverticillium album, Nocardia farcinia, Streptomyces atratus, Nocardia vaccini, Nocardia amarae, and Micromonospora chalcea can grow and degrade pesticides very efficiently. Elgueta et al. (2016) studied the degradation of atrazine and found that the half-life of atrazine decreased to six days by white-rot fungi (Elgueta et al., 2016). The ability of green microalga Chlamydomonas mexicana to degrade atrazine studied by Kabra et al. (2014) and found that microalgae could effectively degrade atrazine by accumulating atrazine in cells and then degrading it, reaching a degradation rate of 14%e36% (Kabra et al., 2014). The isolated Pesticide-degrading bacteria were mainly Pseudomonas, Klebsiella pneumoniae, Bacillus subtilis, etc. Fungi included mycobacterium, Aspergillus, white-rot fungi, etc. Algae included marine chlorella, etc. (Huang et al., 2018). In some common microorganisms listed for pesticide degradation.

5.2 The mechanism of microbial degradation of pesticides Microorganisms on the role of pesticides can be divided into two categories (Huang et al., 2018), a class of microorganisms directly on the role of pesticides, pesticide degradation by enzymatic reactions, often said that pesticide microbial degradation belong to this category; one is through microbial activity Changed the chemical and physical environment and indirectly applied to pesticides. Common modes of action are mineralization, cometabolism, bioconcentration, or cumulative effects and microbial effects on pesticides (Xiaolan et al., 2018a,b). The secondary pollution avoided by bacteria which can convert organic macromolecules into small non-toxic molecules. Studies have shown that mineralization

5. Biodegradation

and cometabolism were the main mechanisms for the further degradation of pesticides and their intermediate products (Ye et al., 2018; Arora et al., 2012; Huang et al., 2018). The whole degradation mechanism was divided into three parts (Chen et al., 2011; Huang et al., 2018). First, Terget adsorption took place on the surface of the cell membrane and was a crucial dynamic equilibrium mechanism as well. Second, across the surface of the cell membrane, the target reached the cell, and the penetrated rate and efficacy is linked to the target isomerism’s molecular structure. Third, there was a fast enzymatic reaction of the xenobiotic target in the membrane (Chen et al., 2011; Huang et al., 2018).

5.2.1 Enzymatic degradation Microbial degradation of pesticides through enzymatic reactions are mainly oxidized, dehydrogenation, reduction, hydrolysis, synthesis, and other types of reactions (Xiaolan et al., 2018a,b). In recent years, microbial degradation was used more frequently because pesticides were used as mainly microbial nutrient, and ultimately decomposed into some small molecules, such as CO2 and H2O (Huang et al., 2018). The development was called enzymatic reaction, which included that the compound first reached the body of the microorganism in a certain manner, and then by a sequence of physiological and biochemical processes under the operation of different enzymes, eventually the pesticide would be totally degraded or broken down into smaller molecular compounds with nontoxicity or less toxicity (Huang et al., 2018). For example, Pseudomonas sp strain ADP used atrazine as the only carbon source, and three enzymes were involved in the first few steps of degradation of atrazine (Huang et al., 2018). The first enzyme was AtzA, which catalyzed atrazine’s hydrolysis dechlorination response to nontoxic hydroxyl atrazine and was a primary biological degradation enzyme of atrazine. AtzB, which catalyzed hydroxy atrazine dehydrochlorination to create N-isopropyl cyanuric amide, was the second enzyme (Huang et al., 2018). The third enzyme was AtzC, which catalyzed the cyanuric acid and isopropylamine formated by N-isopropyl cyanuric amide. Finally, atrazine was degraded to CO2 and NH3 (Huang et al., 2018). As degrading enzymes were much more immune than microbial cells capable of generating such enzymes to abnormally environmental conditions, and the degradable efficiency of enzymes was far higher than that of microorganisms, especially at low pesticide concentrations (Huang et al., 2018). Therefore, it will be a more efficient alternative for humans to use degrading enzymes to purify the Environment that has been poisoned by pesticides. However, owing to the impact of nondegeneration and soil adsorption in the soil, the degrading enzyme was readily inactivated, so it was impossible to sustain the degradable function for a long time (Huang et al., 2018). Also, the poor mobility of the enzyme in the soil and other factors limited the application of degrading enzymes in practice (Huang et al., 2018). Many experiments have found that most of the genes encoding these enzymes are plasmid-controlled (Czarnecki et al., 2017; Huang et al., 2018), for example the biodegradation of 2,4-D was controlled

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Step: 1

Step: 2

Step: 3

•The adsorption of pesticides is a complex balance on the surface of microbial cells, but it also contributes to early degradation in the critical phase of the lag phase.

•Pesticides penetrate the cell membrane through the membrane, the bacteriadetermines its pene tration of the cell membrane in a certain amount of pesticide on the cell membrane permeabilit y, the degradation rate limit stage is pesticide penetration of the cell membrane.This pesticide penetration rate is closely linked to pesticide molecular structure parameters (mainly lipophilic parameters and parameters of steric hindranc). •Pesticides in the cell membrane through the combination with the degrading enzyme enzymatic reaction, which is a rapid process.

FIGURE 17.1 Degradation of pesticide by intracellular enzymes.

by the gene carried on the plasmid (Arora et al., 2012; Huang et al., 2018). Pesticides were degraded through the expression of plasmid gene and chromosome gene in the bacteria (Huang et al., 2018). When the degradation of microbial pesticides is caused by its intracellular enzymes (9), the whole degradation process through three steps (Xiaolan et al., 2018a,b, Fig. 17.1):.

5.2.2 Mineralization There are many chemical pesticides are natural compounds analogues, can be used as a source of microbial nutrients by microbial decomposition, the formation of inorganic, carbon dioxide and water. Mineralization is the best way to degrade (Xiaolan et al., 2018a,b). This is because the pesticide is completely degraded into nontoxic inorganic matter. Shi Lili et al. (2002) studied the degradation of methyl parathion and its degradation mechanism in Pseudomonas vaginalis DLL-1. It was pointed out that DLL-1 bacteria could completely degrade methyl parathion into NO2 and NO3 (Xiaolan et al., 2018a,b). Mineralization was a general term for the conversion of organic compounds into inorganic compounds under the action of soil microbes (Huang et al., 2018). Many chemical pesticides were analogs of natural compounds, and some microorganism had the enzymes to degrade them. They could be used as a source of microbial nutrients and then be degraded to inorganic matters, carbon dioxide, and water by microorganism. Mineralization was an ideal way to degrade because pesticides were completely degraded into nontoxic inorganic substance (Huang et al., 2018).

5.2.3 Cometabolism Cometabolic referred to that some chemical substances like insecticides, fungicides, and herbicides, etc. which did not exist in natural conditions, could be degraded not by bacteria or fungi easily, but only by adding some organic matter such as exogenous or iso-biomass as the primary energy (Zhang et al., 2010; Huang et al., 2018).

5. Biodegradation

Taking a sort of cometabolism as an example, the degradation products of the monomethylamine products of Pseudomonas dendrolimus DR-8 were 2,4-dimethylaniline and NH3, whereas the DR-8 strain could grow with other organic nutrient substrates added as carbon source and energy source instead of meth amidine, meanwhile the degradable products were not completely mineralized (Huang et al., 2018). Cometabolism has played a significant role in pesticides’ microbial degradation (Huang et al., 2018). It should be noted that in most cases, the synergistic effect of a series of reactions instead of one reaction was needed to finish the degradable process of pesticides in the microbial body. For example, Deng et al. (2015) found that Aspergillus niger YAT could fully degrade beta-CY(b-CY) and its intermediates by cometabolism and mineralization, and the entire degradable mechanism was studied, whereas in other pyrethroid degrading strains there was unusual research (Deng et al., 2015; Huang et al., 2018). Some of the synthetic compounds cannot be degraded by microorganisms, but if there is another carbon matrix and energy for the presence of auxiliary matrix, they can be partially degraded, this effect is called cometabolism (Huang et al., 2018). The degradation of the monomethylamine product of Pseudomonas dactylus DR-8 was 2,4-dimethylaniline and NH3, and the DR-8 strain could not grow with monomethylamine as carbon source and energy, Other organic nutrient matrix as a carbon source under the conditions of degradation of methamidine, and the degradation products are not fully mineralized, belonging to the common metabolic type (Xiaolan et al., 2018a,b). The main principle of using microbial remediation of environmental pesticide pollution is the use of organic pesticides as a carbon source, nitrogen source, the complex pesticide compounds into simple compounds, or completely decomposed into CO2, H2O, NH3, thereby reducing pesticide residues in the environment and toxicity. Lin Gan and other cypermethrin as the target pollutants, through enrichment and culture of aerobic treatment tank sludge, obtained a better degradation of the pollutants of the mixed culture of microorganisms, with the microbial degradation of bacteria, the cypermethrin biodegradation the characteristics of the experimental study (Huang et al., 2018). The results showed that the mixed culture could improve the degradation rate of cypermethrin by using cypermethrin as the only carbon source, nitrogen source and energy source, and the appropriate amount of carbon source could increase the degradation rate of cypermethrin (Xiaolan et al., 2018a,b).

5.2.4 Other microbial degradation pathways The degradable ways included oxidation (hydroxylation reactions, like aromatic hydroxylation, aliphatic hydroxylation, N-hydroxylation, epoxidation, N-oxidation, P-oxidation, S-oxidation, oxidative dealkylation, oxidative dehalogenation, and oxidative deamination), reduction (reduction of group, quinone reduction, and reductive dehalogenation), hydrolysis (some esters like thiophosphate, thiocarbamate, etc., which have ester bonds which will be hydrolyzed by bacteria), dehydrogenation, dehalogenation, decarboxylation, condensation, synthesis then on (Huang et al., 2018).

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5.2.4.1 Hydrolysis Under the action of microorganisms, the ester bond and the dialkylamine bond hydrolyze, so that the pesticide detoxification, such as malathion, propanil, and other degradation (Xiaolan et al., 2018a,b).

5.2.4.2 Dehalogenation Fecal hydrocarbon pesticides, within the role of the enzyme, the substituents on the halogen by the H atom or carboxyl, to exchange the loss of toxicity, like DDT degradation into DDE is such a reaction (Xiaolan et al., 2018a,b).

5.2.4.3 Oxidation Microorganisms through the synthesis of oxidase, the molecular oxygen into the organic molecules, especially organic molecules with aromatic ring, insert a hydroxyl or form an epoxide, such as carbendazim and 2,4-D degradation (Xiaolan et al., 2018a,b).

5.2.4.4 Nitro reduction In the pesticide, microorganisms turn N2O into NH2, such as 2,4-dinitrophenol, 2-amino-4-nitrophenol, and 4-amino-2-nitrophenol degradation products; parathion into aminophosphorus (Xiaolan et al., 2018a,b).

5.2.4.5 Methylation Add toxic phenols to methyl groups to passivate them, such as pentachlorophenol, tetrachlorophenol and other degradation (Xiaolan et al., 2018a,b).

5.2.4.6 Demethylation Containing methyl or other hydrocarbon groups, connected to N, O and S, to remove these groups into nontoxic substances, such as dexamethasone degradation of the removal of two N-methyl (Xiaolan et al., 2018a,b).

5.3 Commonly used pesticide degradation of microorganisms Microorganisms play the most role in a variety of biodegradable, so far, a variety of biodegradable pesticides have been isolated, including bacteria, fungi, actinomycetes and algae (Fan et al., 2011; Xiaolan et al., 2018a,b). Bacteria have a spread of biochemical capacity, easy to mutagenesis, within the biological restoration of the most position, of which the foremost active Pseudomonas strains, a spread of pesticides \\ fungicides and herbicides (Wang et al., 2012; Xiaolan et al., 2018a,b) play a highly effective degradation The At present, the study of bacteria is more extensive (Xiaolan et al., 2018a,b).

5.4 Microbial degradation of pesticide technology 5.4.1 Application of transgenic technology Molecular biology, genetics and other disciplines of rapid development led to the emergence of a variety of biotechnology, coupled with bioinformatics, proteomics,

6. Factors affect biodegradation

genomics and other new disciplines quickly rise, motivating people for the creation of superpesticide pollution degradation bacteria’ provides a good condition (Xiaolan et al., 2018a,b). The mechanism of degradation and regulation of degrading enzyme gene was clarified at the DNA level, and more degradation genes were cloned and the highly degraded microorganisms were prepared (Xiaolan et al., 2018a,b). The results showed that the degradation mechanism of the biodegradable microorganisms and the pesticide pollution degradation plasmids and pesticide pollutiondegrading enzymes were more deeply studied (Xiaolan et al., 2018a,b). Of the gene pool, the use of modern genetic engineering to build more efficient “pesticide pollution degradation engineering bacteria” or “pesticide pollution degradation enzyme expression system,” broaden the degradation spectrum, improve the degradation capacity (Xiaolan et al., 2018a,b).

5.4.2 Construction and application of multistrain complex system Several experiments have focused on pure culture of a single microbial strain on biodegradation of pesticide contaminants, and it has now been shown that the pure culture of a single strain is not as successful as mixed culture (Xiaolan et al., 2018a,b). Because a single microorganism does not have the genetic information of all the enzymes required for biodegradation, and Many pure cultures have observed that during biodegradation, toxic intermediate content aggregation, thus comprehensive mineralization typically involves one or more of the nutrient flora (such as fermentation-hydrolysis bacteria, sulfur bacteria, acetic acid forming bacteria and methanogens) during their time of acclimatization in the refractory compound is not adequate to evolve the full metabolic pathway (Xiaolan et al., 2018a,b). An aspect of microbial degradation, through many microbial relays and synergistic results, after a multi-step reaction to totally mineralized toxic compounds, microbial community activity is more immune to biodegradation of toxic substances (Xiaolan et al., 2018a,b).

5.4.3 Application of immobilized microbial technology Immobilized microbial technology is a new type of biotechnology that emerged in the 1980s by locating free cells or enzymes in a defined spatial region by chemical or physical means to keep them active and reusable, Bioreactor microbial cell concentration and purity, and to maintain high efficiency bacteria, secondary pollution and other characteristics (Xiaolan et al., 2018a,b). The use of immobilization technology to fix the degradation of microorganisms and enzymes, and then used to deal with pesticides contaminated soil or water, has good prospects for development (Xiaolan et al., 2018a,b).

6. Factors affect biodegradation Pesticides in the environment are mainly adsorption and degradation of two kinds of where the degradation of pesticides can be divided into biodegradable and

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nonbiodegradable two ways (Xiaolan et al., 2018a,b). In the light, heat and chemical factors under the action of degradation of the phenomenon of nonbiodegradable; and in plants and animals or microorganisms in vivo degradation of biodegradation. Biodegradation is mainly microbial degradation in pesticide degradation to occupy a dominant position (Xiaolan et al., 2018a,b).

6.1 Environmental factors Pesticides are effected by number of environmental factors into the environment, such as: temperature, humidity, pH, water content, organic matter content, viscosity and climate (Xiaolan et al., 2018a,b). Generally, in the case of high temperature and humid, organic matter rich, pH alkaline, pesticide is easy to be degraded low (Xiaolan et al., 2018a,b). Scientists were used to study the degradation of the soil in the soil, and the degradation efficiency of the pesticide in the soil was improved when the soil was added with compost, stem and sawdust to improve the organic matter content (Xiaolan et al., 2018a,b). The degradation would be affected by temperature, humidity, salinity, pH, nutrition, carbon dioxide, oxygen, substrate concentration, surfactant, etc. (Sartoros et al., 2015; Huang et al., 2018). Bacteria or their enzymes needed a suitable temperature, pH and substrate concentration (Nakajima and Shigeno, 2014; Huang et al., 2018). The number of benzene rings of PAHs had a great impact on the microbial degradation of PAHs. The breakdown of two naturally occurring rings and tricyclic compounds (naphthalene, phenanthrene, anthracene, fluorine, etc.) just takes a short period, and these compounds may be mineralized by microorganisms using PAHs as the primary source of carbon (Acevedo et al., 2011). However, the four-ring and other multiring PAHs with high molecular weight were stable in the environment so that they were difficult to be degraded. But, the white-rot fungi could degrade these compounds by metabolism (Acevedo et al., 2011; Huang et al., 2018). Generally, with the increase of the number of benzene rings of PAHs, octanol/ water partition coefficient increased, and the degradable rate was lower and lower (Huang et al., 2018). Surfactant could affect the solubility of PAHs in soils, the balance of adsorption and desorption, and the interaction between PAHs and soil microorganism, thus further change the bioavailability of PAHs. For example, In order to improve the solubility of PAHs, promote the transport of PAHs, and thereby improve the bioavailability of PAHs, Huang et al. (2018) used a way to minimize the interfacial stress between soil and water. The bioavailability of PAHs may, however, be inhibited due to the toxic effects of surfactants on microorganisms or the usage of nontoxic surfactants as a microbial growth matrix (Huang et al., 2018). In addition, the effect of surfactants on the bioavailability of different types of PAHs in soils was different, enabling the addition of surfactants to increase the solubility of PAHs in the aqueous phase, facilitate the transition of solid phase to the water phase, boost bioavailability, and decrease matrix surface and interfacial stress (Huang et al., 2018).

6. Factors affect biodegradation

One of the most important limiting factor for microbial growth and maintenance of population was lack of nutrients (Huang et al., 2018). Researchers’ studies have shown that preserving the standard C: N: P ratio will stably facilitate the deterioration of PAHs in the contaminated climate. Ammonia and phosphate were also added to change the C: N: P ratio in biorepair in order to have full degradation and to accelerate the purification rate (Huang et al., 2018). Temperature and humidity were the most important factors, which affected the growth and reproduction of bacteria (Arbeli and Fuentes, 2010; Huang et al., 2018). The degradation and mineralization of biaryl compounds in soil and compost by Ralstonia and Pickettii bacteria has been investigated and it has been found that nonionic surfactants between 80 can enhance the use of biaryl compounds by bacteria under suitable soil moisture conditions, such as biphenyl, 4chlorobiphenypheny (Zhu et al., 2015; Huang et al., 2018). Researchers thought that the effect of organic substrate content on pesticide’s degradation in composting was greater than that of bacteria content when compost was mixed with soil contaminated by PAHs. Because bacteria did not produce energy and need other carbon and energy source, so nutrition was more important when bacteria degraded pesticides by cometabolism (Huang et al., 2018).

6.2 Effect of pesticide structure Pesticide molecular structure, the use of pesticide concentration and pesticide drug history also affect the degradation performance of pesticides (Xiaolan et al., 2018a,b). The rate and efficiency of microbial degradation of pesticides depends on Pesticides’ own factors, such as their molecular weight, spatial structure, the number and type of substituents, substituted characteristics and location (Chrzanowski et al., 2012; Huang et al., 2018). The polymer compound was generally less biodegradable than that of the low molecular weight compound. The polymer and composite were more resistant to biodegradation, but more easily degraded with a simpler space structure (Huang et al., 2018). Pesticides because of its molecular structure and physical and chemical properties of different biodegradability sensitivity is very different. For example, due to the addition of one chlorine atom to the fifth C atom, 2,4-D and 2,4-T, the time needed for degradation is increased from 14 to 200d, 2,4,5-T The degradation by microorganisms is very difficult (Xiaolan et al., 2018a,b). Microbial degradation of rhizosphere was the main route of phytoremediation on soil contaminated by polycyclic aromatic hydrocarbons (PAHs) (Huang et al., 2018). A relatively minor pathway was plant absorption, and mixed planting could concurrently increase the efficiency of these two ways. For different kinds of PAHs, plants were easier to absorb two to four ring PAHs (Huang et al., 2018). The use of herbicides has become an indispensable means of agricultural production, and thus many problems of environmental pollution have become increasingly prominent, such as the threat to the living environment and excessive pesticide content of agricultural and sideline products (Huang et al., 2018).

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Then, contaminated agricultural products got into human’s body and harm human’s health by the bioaccumulation of food chain and so on (Huang et al., 2018). Many of the new pollutants were biologically heterologous organic compounds synthesized that did not occur in nature, also displaying a clear tolerance to microorganism degradation (Huang et al., 2018). It can be understood that the time of entry into nature of these compounds was relatively limited, so that the metabolic mechanisms of degradation of such compounds have not evolved by a single microorganism (Huang et al., 2018). Since the mineralization and cometabolism of natural microbial populations could slowly degrade some hazardous compounds in nature, this was a new challenge for the microbial world (Huang et al., 2018). The process of microbial degradation was very slow, and it may need to change some structure (Huang et al., 2018). The natural evolutionary process of the microorganism was clearly unable to meet the degradation requirements of microbial pesticides as compared to the currently commonly used synthetic bio heterologous substances, as the pace of the process was far from meeting what the environment and humans needed (Huang et al., 2018). Thus, the balance of the entire ecosystem would be destroyed after a long-term effect (Ye et al., 2018). Therefore, it was very important and urgent to study some of the methods that can make microbial flora achieve maximum degradation of pesticide in a relatively short time (Huang et al., 2018).

6.3 The impact of microorganisms In the activity of microorganisms, the primary way of degradation of pesticides is carried out, so the degradation of pesticides has a big effect on pesticides. The variety of microbes, the number of large, is conducive to the degradation of pesticides (Xiaolan et al., 2018a,b). The degradation of pesticides in situ is usually achieved by a consortium of microbes rather than a single species. Pure culture studies do, however, allow the mechanisms by which the pesticide is metabolized to be elucidated. The mechanisms for transport of the pesticide into the cell, degradation pathways and induction and regulation of degradative pathways can be studied.

7. Current scenario At present, there are many researchers that were devoted to microbial degradation of pesticides (Singh and Singh, 2016; Huang et al., 2018). For example, in the 1980s, there was a form of biological technology called immobilized bacteria technology that increased, namely using free cells or enzymes fixed in limited space and holding them active in the meantime, which can also be reused (Huang et al., 2018). This technology was characterized by efficient use of two strains with low pollution (Huang et al., 2018). Construction of the system of several bacteria allowed for several bacteria to solve the problem of the incomplete transformation of single strain (Racke et al., 2015). A study discussed the microbial cell’s surface display technology that developed in

7. Current scenario

the middle of 1980s (Huang et al., 2018), This procedure was successful, showing a method of combining exogenous protein (this protein has enzyme activity) with degradable strain, and could combine transport and secretory functions to make the exogenous protein better expressed. Finally, the exogenous protein was incorporated in the cell membrane surface and the specific function of the normal exogenous proteins played a role. This technique created direct contact between bacteria and pesticide residues, which not only simplified the protein purification process, but also increased the degradable rate of protein purification (Buvaneswari et al., 2018; Huang et al., 2018). Moreover, in 1994, Stemmer et al., an American scientist, advanced simulated DNA shuffling in vitro technology found in the Darwinian theory. The reorganization technology substantially enhanced enzyme activity and did not require the enzyme’s three-dimensional structure determination (Li et al., 2016; Huang et al., 2018). Many studies have been performed on the degradable plasmid herbicides 2,4-D and 2,4,5-T, and these studies have shown that the dominant 2,4-D degrading bacteria are Peseudomonas sp. Alicaligenes sp., and Containing the pjP4 plasmid Alicaligenes eutophus JMP134d (Huong et al., 2008, 2018). Huang et al. (2018) used Southern hybridization and plasmid curing to get the fact that the naphthalene dioxygenase (ndo) gene of PAH degrading bacteria Pseudomonas sp. would be immobilized on a large self-transmissible plasmid and then transferred to thermophilic strains, and similar temperature optimum was also observed (Huang et al., 2018). There was a lot of plasmid research in the isolation and screening of degrading bacteria strains all over the world, but there were very few on degradable bacteria (Huang et al., 2018). Most of the degrading bacteria were applied directly in the pot experiment (Huang et al., 2018). The results of a number of researches showed that the degrading bacteria isolated from both pot experiment and field experiment had good degradation, and the degradable rate even achieved more than 70%. The degradable rate of most strains was more than 90%, which greatly shortened the half-life (Huang et al., 2018). Some experiments have shown that certain enzymes can withstand changes in environmental conditions, while the bacteria producing this enzyme cannot withstand changes in environmental conditions (Huang et al., 2018). For example, Parathion Hydrolase could tolerate salt’s concentration as high as 10%, 1% of the solvent concentration, and 50 C of the temperature, but Pseudomonas, which could produce this enzyme in this condition cannot grow. The immobilized enzyme not only had the good purified effect of CY, but also degraded organophosphorus and pyrethroid pesticides (Huang et al., 2018). An unavoidable trend, which was close cooperation between the composite nature of bacteria and compliance with the laws of nature, was the microbial degradation of pesticide contamination by using composite structures with a variety of microbial taxa (Huang et al., 2018). A good way to deal with contaminated soil has been to inoculate artificially composite microorganism systems for pesticide contamination in the soil or to increase the use of agricultural organic waste composting. The garbage of modern city life, organic solid waste, sewage sludge included

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significant quantities of organic contaminants and heavy metals, and a large amount of pesticide residues and other contaminants were all included in agricultural organic solid waste. In the composting process, the pollutants were eliminated by microbial degradation and volatilization, leaching, photolysis, chelation, complexation, and so on (Kang et al., 2010; Huang et al., 2018). At the same time, the active compost contained a composite microbial system and it was more likely to become the dominant flora of contaminated soils (Huang et al., 2018). The composting system was therefore not only able to remove waste, but also to obtain high-quality compost products that played a major role in sustainable development for environmental pollution control and agricultural control (Huang et al., 2018). The author considered that the establishment of cooperative relationships between strains could not only improve the effectiveness of the composite system for the decomposition of lignocellulose, but also improve the long-term stability of the constituent organisms, and it was not easy to contaminate them (Huang et al., 2018). On this basis, the complex system gave the function of pesticide decomposition, which had a strong ability to decompose a variety of pesticides and it had a well applicable effect (Huang et al., 2018). In short, while initial progress had been made in the microbial degradation of pesticide residues and most types of microbial strains were identified to degrade pesticides, the functional implementation of microbial bioremediation was often affected because the efficiency of degradation was poor (Huang et al., 2018). The microbial degradation of pesticide residues was still a problem that needed to be overcome (Huang et al., 2018).

8. Conclusion Organic phosphorus, organic arsenic, carbamate, pyrethroid, chloronicotinyl insecticide, and several other fungicides are mostly used in agricultural pesticides, and so forth. Many pesticide-degrading microorganisms could be screened from natural waste or soil, including fungi, actinomycetes, algae, and other microbial strains of bacteria. Pseudomonas, Klebsiella sp., Bacillus subtilis, etc. were bacteria. Trichoderma spp., Aspergillus spp., white-rot fungi, etc., were fungi. The algae had chlorella from the sea, and so on. In comparison to conventional approaches, such as the method of physical degradation, the method of chemical degradation, and so on, the method of microbial degradation has been extensively used in pesticide degradation. This technique was highly effective, low cost, and had a positive impact on degradation. The microorganism used such pesticide compounds as food and broke them down into small molecules, and mineralization and cometabolism were the primary methods of degradation. Many influences, such as the form of chemical, the form of microorganism, and the atmospheric temperature, humidity, acidity, and air composition, have affected the degradation. The aim of these experiments was to evaluate the most appropriate microorganism for various pesticides, the most appropriate methods of degradation and the ecosystem of degradation, which provided a more convenient guide for future study.

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Nakajima, T., Shigeno, Y., 2014. Polyester Plastic-Degrading Microorganism, Polyester Plastic-Degrading Enzyme and Polynucleotide Encoding the Enzyme. EP 1849859B1. Nanseu-Njiki, C.P., Dedzo, G.K., Ngameni, E., 2010. Study of the removal of paraquat from aqueous solution by biosorption onto Ayous (Triplochiton schleroxylon) sawdust. J. Hazard Mater. 179, 63e71. Nicolopoulou-Stamati, P., Maipas, S., Kotampasi, C., Stamatis, P., Hens, L., 2016. Chemical pesticides and human health: the urgent need for a new concept in agriculture. Front. Public Health 4, 148. https://doi.org/10.3389/fpubh.2016.00148. Racke, K.D., Skidmore, M., Hamilton, D.J., Unsworth, J.B., Miyamoto, J., Cohen, S.Z., 2015. Pesticide fate in tropical soils. Pest Manag. Sci. 55, 219e220 (CrossRef). Rauh, V.A., Garcia, W.E., Whyatt, R.M., Horton, M.K., Barr, D.B., Louis, E.D., 2015. Prenatal exposure to the organophosphate pesticide chlorpyrifos and childhood tremor. Neurotoxicology 51, 80e86. https://doi.org/10.1016/j.neuro.2015.09.004. Romero-Aguilar, M., Tovar-Sa´nchez, E., Sa´nchez-Salinas, E., Mussali-Galante, P., Sa´nchezMeza, J.C., Castrejo´n-Godı´nez, M.L., Danta´n-Gonza´lez, E., Trujillo-Vera, M.A., Ortiz-Herna´ndez, M.L., 2014. Penicillium sp. as an organism that degrades endosulfan and reduces its genotoxic effects. SpringerPlus 3, 536 (CrossRef, PubMed). Sagar, V., Singh, D.P., 2011. Biodegradation of lindane pesticide by non white-rots soil fungus Fusarium sp. World J. Microbiol. Biotechnol. 27, 1747e1754 (CrossRef). Salman, J.M., Hameed, B.H., 2010. Effect of preparation conditions of oil palm fronds activated carbon on adsorption of bentazon from aqueous solutions. J. Hazard Mater. 175, 133e137. Sartoros, C., Yerushalmi, L., Be´ron, P., Guiot, S.R., 2015. Effects of surfactant and temperature on biotransformation kinetics of anthracene and pyrene. Chemosphere 61, 1042e1050 (CrossRef, PubMed). Sharma, R.K., Kumar, A., Joseph, P.E., 2008. Removal of atrazine from water by low cost adsorbents derived from agricultural and industrial waste. Bull. Environ. Contam. Toxicol. 80, 461e464. Shi, Li-li, Lin, Yu-lock, et al., 2002. Degradation of methyl parathion pesticide by DLL-1 bacteria and its degradation mechanism. J. Ecol. Rural. Environ. 3. Singh, N., 2009. Adsorption of herbicides on coal fly ash from aqueous solutions. J. Hazard Mater. 168, 233e237. Singh, B., Singh, K., 2016. Microbial degradation of herbicides. Crit. Rev. Microbiol. 42, 245e261 (CrossRef, PubMed). Sola`, M., Riudavets, J., Agustı´, N., 2018. Detection and identification of five common internal grain insect pests by multiplex PCR. Food Contr. 84, 246e254 (CrossRef). Soloneski, S., Kujawski, M., Scuto, A., Larramendy, M.L., 2015. Carbamates: a study on genotoxic, cytotoxic, and apoptotic effects induced in Chinese hamster ovary (CHO-K1) cells. Toxicol. Vitro 29, 834e844. https://doi.org/10.1016/j.tiv.2015.03.011. Song, Y., Jia, Z.C., Chen, J.Y., Hu, J.X., Zhang, L.S., 2014. Toxic effects of atrazine on reproductive system of male rats. Biomed. Environ. Sci. 27, 281e288. https://doi.org/10.3967/ bes2014.050. Suciua, N.A., Capri, E., 2009. Adsorption of chlorpyrifos, penconazole and metalaxyl from aqueous solution by modified clays. J. Environ. Sci. Health B 44, 525e532. Sudhakar, Y., Dikshit, A.K., 2008. Removal of endosulfan from water using wood charcoaladsorption and desorption. J. Environ. Eng. 134, 102e109. Tang, W., 2018. Research progress of microbial degradation of organophosphorus pesticides. Prog. Appl. Microbiol. 1, 29e35.

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Upadhyay, L.S., Dutt, A., 2017. Microbial Detoxification of Residual Organophosphate Pesticides in Agricultural Practices. In: Microb. Biotechnol. Springer, Singapore, pp. 225e242. Verma, J.P., Jaiswal, D.K., Sagar, R., 2014. Pesticide relevance and their microbial degradation: a-state-of-art. Rev. Environ. Sci. Technol. 13, 429e466 (CrossRef). Wang, G., Chen, H., Meng, B., et al., 2012. Preparation of Pseudomonas sp. Strain CTN-3 to polluted soil of chlorothalonil. Chin. J. Appl. Ecol. (3). Wolfand, J.M., LeFevre, G.H., Luthy, R.G., 2016. Metabolization and degradation kinetics of the urban-use pesticide fipronil by white rot fungus trametes versicolor. Environ. Sci. Process. Impacts 18, 1256e1265 (CrossRef, PubMed). Xiao, P.F., Mori, T., Kondo, R., 2012. Bioconversion of heptachlor epoxide by wood-decay fungi and detection of metabolites. Adv. Mater. Res. 518, 29e33 (CrossRef). Xiaolan, Y., Dong, F., Lei, X., 2018a. Microbial resources and ecology - microbial degradation of pesticides. Nat. Resour. Conserv. & Res. 22e28. Xiaolan, Y., Dong, F., Lei, X., 2018b. Microbial Resources and Ecology - Microbial Degradation of Pesticides. Ye, X., Dong, F., Lei, X., 2018. Microbial resources and ecology-microbial degradation of pesticides. Nat. Resour. Conserv. Res. 1 (CrossRef). Zhang, C., Jia, L., Wang, S.H., Qu, J., Li, K., Xu, L.L., Shi, Y.H., Han, Y.C., 2010. Biodegradation of beta-cypermethrin by two Serratia spp. with different cell surface hydrophobicity. Bioresour. Technol. 101, 3423e3429 (CrossRef, PubMed). Zheng, W., Guo, M., Chow, T., Bennett, D.N., Rajagopalan, N., 2010. Sorption properties of greenwaste biochar for two triazine pesticides. J. Hazard Mater. 181, 121e126. Zhu, M., Mccully, L.M., Silby, M.W., Charles-Ogan, T.I., Huang, J., Brigham, C.J., 2015. Draft genome sequence of Ralstonia sp. MD27, a poly3-hydroxybutyrate-degrading bacterium, isolated from compost. Genome Announc. 3 e01170-15. (CrossRef, PubMed).

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An ecofriendly approach toward waste management and environmental safety through microorganisms

18

Kunwali Das1, Suraj Chetri2, Priya Khadgawat3, Sidak Minocha3, Aveepsa Sengupta1, Bipin Kumar Sharma1, Ashutosh Kumar1 1

Department of Microbiology, Tripura University (A Central University), Agartala, Tripura, India; 2 Department of Zoology, Cotton University, Guwahati, Assam, India; 3Department of Genetics, University of Delhi, New Delhi, Delhi, India

1. Introduction The microbial population can be considered a boon to humankind as well as to the environment. It is vast and dynamic and generally cosmopolitan in nature as it has made its way to almost all domains on the earth. They are found in the human body, polar ice, deep sea, deserts, in alimentary canal of insects, etc. The population, comprises bacteria, fungi, viruses, algae, protozoa, and archaea with varying sizes and shapes. The immense diversity of microorganisms helps in ensuring global environmental safety as well as understanding the problems related to the environment across the globe. The microbial species not only help in managing the environmental issues but also help in maintaining the stability of the ecosystem. The microorganisms also have the additional property of resisting themselves from destruction by the environment. Pathogenic suppression is yet another property exhibited by some microbial species. Water bodies like rivers, lakes, wetlands, etc. harbor a wide variety of valuable microorganisms. Microbes are often ubiquitous in nature, but the lesser-known fact about these organisms is that they can result in a safer environment when exploited adequately. The generation of large amounts of wastewater as well as sewage by humans needs a highly efficient treatment before discharge. The treatment strategies based upon various physical, chemical, and mechanical processes are proven to be less efficient, high budget, labor-intensive, and cause secondary pollution. These limitations have created a void making way for newer approaches based upon microbial technologies for effective waste management. The microorganisms can be termed as the chief recyclers of the environment. The far-reaching impacts of the microorganisms can be observed in the field of environmental biotechnology. They find greater use in such areas as they offer numerous

Development in Wastewater Treatment Research and Processes. https://doi.org/10.1016/B978-0-323-85657-7.00021-3 Copyright © 2022 Elsevier Inc. All rights reserved.

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benefits to humankind along with the environment without causing any harm to the surrounding. Various processes like oxygen production, decomposition of organic matter, and nutrient supply to plants are carried out by the microorganisms. The havoc caused to the environment in recent years is a major issue that requires sufficient attention at present times. That is where the potent role of microorganisms comes into play. The increased anthropogenic activities around the globe have lead to the emergence of various diseases. Microbial biosensors have been used for several years to get process control data in food processing, fermentation, and pharmaceuticals. These organisms can be used as an effective means for an ecofriendly waste management procedure along with environmental safety. Flocculation is one of the processes which is helpful in managing wastes where microorganisms result in complete stabilization on separation from the liquid phase (Adebayo and Obiekezie, 2018). Another important population of microorganisms is fungi, which result in the stabilization process of organic waste. The only limitation of fungi is that they remain nonfunctional in harsh environmental conditions. Unlike bacteria and fungi, algae do not need to metabolize organic waste, rather they meet their energy requirements from sunlight itself. When sunlight is not available; they acquire energy from the organic compounds present in the wastes. Viruses are also effective in checking the microbial pollution of waste that persists in the environment. Protozoa on the other hand act as an important organism for clarification of the effluent released from the industries (Adebayo and Obiekezie, 2018). Recycling of waste matter from agriculture is carried out primarily by microorganisms. Composting is the process by which microorganisms utilize the agricultural residues to increase the fertility of the soil, increase the richness of soil biodiversity, and reduce certain ecological risks without hampering the environment. Microbe-based biofertilizers are considered to an extent and upcoming alternative to conventional chemical fertilizers, which are known to have toxic effects on crop plants, soil as well as groundwater. Microorganisms such as Cyanobacteria, some fungi as well as bacteria that promote plant growth are known to have biofertilizer like activities. This has been extensively utilized in the agricultural field to ensure enhanced crop production and food safety without the cost of hampering the environment (Mahanty et al., 2017). Similarly, the waste from medical sectors can lead to a hazardous and toxic environment (Heera et al., 2014). Therefore, biomedical wastes need to be managed tactfully. Microorganisms can be used for the handling biomedical wastes in an efficient and ecofriendly way. In recent years, radioactive wastes generated from nuclear power plants have been a matter of concern. Microbial processes including the degeneration of cellulosic materials and gas generation can be employed effectively in order to mitigate the damage caused by the radioactive waste released into the environment without treatment (Beaton et al., 2019). The organic matter in the wastes can be transformed into renewable energy sources like hydrogen and methane using anaerobic biological procedures, called microbial electrolysis cells (Katuri et al., 2019).

2. Microorganisms in the environment

2. Microorganisms in the environment 2.1 Bacteria Bacteria are considered the simplest alive organisms. They are prokaryotic and some of them are photosynthetic. Morphologically there are three types of bacteria. These include rod shaped, spherical and curved or helical shaped. They can be aerobic (living in the oxygen present environment), anaerobic (living in the oxygen absent environment), and facultative anaerobes (can live in both environments). Cyanobacteria capture light for the process of photosynthesis. Cyanobacteria are believed to convert early reducing atmosphere as it has the ability to perform oxygenic photosynthesis. About 20%e30% of the earth’s photosynthetic productivity is contributed by cyanobacteria. They have a significant contribution to ecological succession and evolutionary processes due to their ability to reduce carbon and nitrogen in anaerobic conditions. To keep the environment in a balanced state, microorganisms have always been beneficial. Bacteria have been found effective in recycling living materials in a natural process. Environmental protection and waste management are the most effective areas where bacteria have been employed. During sewage treatment, anaerobic bacteria are being used for the reduction of organic matter and methane gas production in certain sludge solids. Some bacteria are also used in water treatment, where a gelatinous layer is formed by the bacteria for the removal of particulate as well as dissolved matter from the water. In the treatment of soil, the nitrogen cycle plays an important role to make the atmospheric nitrogen available to the plants. In such areas, the role of symbiotic bacteria living in the root nodules of leguminous plants comes into play. The symbiotic bacteria may belong to the genera- Rhizobium, Bradyrhizobium, Azorhizobium, Mesorhizobium, Senorhizobium, etc. (Spaink et al., 1998; Sprent, 2002). The bacteria not only help in nutrient availability but also protects the plant from diseases, helps in hormone production for growth, maintains the immune system, and also help in producing stress responses (De Vrieze, 2015). Various bacterial species have been used in recent years during the conversion of agricultural waste and urban waste into certain fuels in a usable form. Some other bacteria also help in the digestion of toxic wastes like chemical solvents for the production of electricity. In such a way, energy can be generated with the use of platinum electrodes, which generate electric currents. The distinct biochemical properties of bacteria make them a powerful tool in waste management. They also help in the metabolization of organic compounds found in certain wastes. Aerobic waste treatment systems mostly employ bacteria that can utilize organic compounds. Flocculation is one of the most important processes of bacteria which may improve biological waste management. Zoogloea ramigeria is one such flocculating bacteria that enhance environmental conditions (Adebayo and Obiekezie, 2018). With the use of various types of bacteria, waste can be efficiently managed and the environment can be kept safe with the employment of such practices.

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2.2 Fungi Fungi are nonphotosynthetic eukaryotic organisms. They have similarities with plants but do not possess chlorophyll and hence cannot make their food. They obtain their food by absorbing nutrients from the surrounding environment. Various types of fungi include club fungi (mushrooms), sac fungi (yeast), and zygote fungi (mold). They are generally aerobic or facultative aerobic organisms. Their cell wall is composed of chitin. They are the principal decomposers of carbon compounds on earth. Waste disposal and management have always been a matter of concern in recent years. Unscientific methods of waste management have led to environmental problems. Microorganisms have always been an ecofriendly solution to such problems. They can be used to produce fuels, manure, etc. In the past few years, solid waste is managed with the use of composting techniques through mushroom fungi. The fungi break down organic matter and convert it into humus. Humus, which is a nutrientrich matter, helps to increase nutrient content in soil and the addition of the fungi helps in the biological conversion of solid wastes in certain edible forms which can in turn be used as food and in pharmaceuticals (Jebapriya et al., 2013). Mushroom fungi also have the ability to remove toxic substances like metals from wastes (Hatvani and Me´cs, 2003; Stamets, 2006). Biological conversion of agricultural wastes has been efficient with the cultivation of fungi. They produce certain enzymes which degrade the toxic matter and contribute to the mineralization of detrimental substances. The activities of enzymes involved in oxidation and hydrolysis contribute to waste bioconversion. The exoenzymes from filamentous fungi are also beneficial in agricultural waste management (Cohen and Hadar, 2018). Fungal enzymes from different species of fungi like peroxidases, laccases, and tyrosinases assist significantly in the degradation of persistent organic pollutants (POPs) found in the solid and liquid parts of discharged municipal and industrial waste (Ku¨es, 2015). The only drawback of fungi is that they are unable to function during extremely harsh environmental conditions. Various fungi play great role in waste water and sewage treatment. Aspergillus sp., Penicillium sp., etc. filamentous fungi are abundant in waste water and they help to metabolize organic residues (Akpor et al., 2013).

2.3 Viruses Virus consists of a nucleic acid segment surrounded by a protective protein coat. They can multiply within the living host cell only as it needs the host’s environment and nutrients for their reproduction. Viruses can be classified into DNA and RNA viruses. DNA viruses include Adenoviruses, Herpes virus, Bacteriophages, and Hepatitis B virus. RNA virus includes retro virus, Hepatitis virus A, C, and D, influenza virus, and hemorrhagic fever virus. Viruses are microorganisms that are the result of an assemblage of biopolymers and have the ability to assemble and multiply as new

2. Microorganisms in the environment

viral particles inside a variety of prokaryotic and eukaryotic cells. The use of viruses in waste management is very limited, very little is known about it. Viruses are mainly employed in areas where pathogenic forms of bacteria are to be removed or destroyed from various wastes. Numerous viruses affect bacteria and are known as bacteriophages. These bacteriophages are utilized in certain waste management processes where bacterial cultures need to be degraded in the environment. The bacteriophages also play role in the detection of diverse microbial populations persisting in the environment (Adebayo and Obiekezie, 2018).

2.4 Protozoa Protozoa are single-celled organisms and cosmopolitan in distribution. It includes free living organisms such as Ameba, Paramaecium, Euglena, Noctiluca, Elphidim, and parasitic organisms such as Plasmodium, Entamoeba, Monocystic, Giardia, Trypanosoma etc. Protozoa produce cysts that enable them to survive in harsh environmental stress like drought, heat, and freezing. Protozoans are a complex organization of different interacting organisms with varying levels of resistance or tolerance to the pollutants present in wastes. The wastewater released from industries, agricultural fields, etc., can be purified with the use of protozoa. The protozoan species help in the improvement of the effluent quality of discharged waste. There are a vast number of heavy metals found in sewage and also in the waste released from the industries, where the protozoan community act upon. The protozoan species are known to excrete certain mineral nutrients that enhance the usage of carbon sources by bacterial species during carbon mineralization (Bloem et al., 1988). One of the most important qualities exhibited by the protozoan community is grazing on bacteria. They are mostly known as bacterivorous grazers. The protozoans also act as indicators of increasing levels of toxicity in the wastewaters. The increasing levels of toxicity can be primarily associated with the presence of heavy metals. Many organic and inorganic materials are known to be released into the surroundings by the protozoans. These are mainly nutrients and certain stimulatory compounds recycled and affect bacterial growth and physiology (Ju¨rgens and Matz, 2002).

2.5 Algae The utilization of microalgae has been economically viable as well as ecofriendly in nature. The use of microalgae in waste management systems has gained much importance. They are known to exhibit multiple roles including the bioremediation of waste, generation of important biomass that may be utilized in various other industries like, food and pharmaceutical industries (Renuka et al., 2015). Algal species like Chlorella and Dunaliella are included in waste management systems. The effluent from industries, agricultural fields, nuclear plants, etc., can be clarified using microalgae. The toxic minerals like arsenic (As), cadmium (Cd), lead (Pb), and mercury (Hg) can be removed with the help of microalgae. They possess a disinfecting

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property within them because of their ability to produce oxygen upon the rise of pH levels. This is one of the most advantageous properties of microalgae. Algae are also incorporated in the waste management systems to assist in the removal processes of coliform bacteria. Sometimes, algae are being used to lessen biological oxygen demand (BOD) and chemical oxygen demand (COD). For the removal of compounds like phosphorous and nitrogen, certain species of algae are used. Some of the algal species also find use during the removal of heavy metals (Abdel-Raouf et al., 2012).

2.6 Archaea Archaea are considered as the oldest form of life on earth. Archaea neither needs oxygen nor requires sunlight for photosynthesis. They absorb CO2, H2S, and N2 from the environment, and give off methane as a waste product. Until many years, the importance of archaea was not known to humankind. But recent developments and studies related to biological waste management systems have led to the wide acceptance of the use of archaea in these areas. The use of archaea in waste management systems is being found to be responsible for certain biological processes like mineralization of carbon, methane production, nitrification, and denitrification (Li et al., 2018). The utilization of archaea in these systems has led to the conversion of certain polluting agents into various ecofriendly products with minimal chemical and energy input. Several methanogenic archaeal species are found to be beneficial in biomethane production from the waste. The process of biomethane production from the decomposition of organic matter by the anaerobic bacteria requires the association of several organisms. At first, the organic materials from the waste is converted into some organic acids. These organic acids are further utilized by the methanogenic archaea which decompose the organic acids in order to produce biogas (Tabatabaei et al., 2010).

3. Microorganisms for waste management Many natural and artificial ecosystems are highly maintained by the microorganisms as they can recycle living and nonliving materials. They play a major role in controlling the quality of the environment. To sustain the humankind in the world, humans have manipulated various natural resources and converted them into simpler convenient forms. This results in pollution and also accumulates a large quantity of wastes in the environment. Various wastes that are produced by humans include industrial waste, municipal waste, agricultural waste, biomedical waste, radioactive waste, etc. (Fig. 18.1). The role of microorganisms in waste management is discussed later.

3.1 Industrial waste With the increase in the number of populations globally, there is also an increase in the industrialization process to meet the people’s needs. The beneficial outcome of

3. Microorganisms for waste management

FIGURE 18.1 Different types of human-generated wastes. Figure adapted, with permission, from Mani, S., Chowdhary, P., Zainith, S., 2020. Microbes mediated approaches for environmental waste management. In: Chowdhary, P., Raj, A., Verma, D., Akhter, Y. (Eds.), Microorganisms for Sustainable Environment and Health. Elsevier, 17e36, ISBN 9780128190012. https://doi. org/10.1016/B978-0-12-819001-2.00002-4 © 2020 Elsevier Inc.

each industry comes with lots of waste materials. Proper management and disposal of waste materials are of the utmost importance to maintain a healthy environment. With technological innovation, microorganisms can be used to degrade various industrial waste into simpler harmless products. This technological innovation utilizes microorganism’s cellular metabolism to degrade the wastes. Microorganisms possess different biological mechanisms in them which help them to remove toxic materials from the environment. These include the complexation of exopolysaccharides, biosynthesis of metallothionins, adsorption to cell surfaces (Sharma et al., 2013). Micrococcus luteus and Azotobacter sp known to immobilize lead from high concentration lead salts areas (Tornabene and Edwards, 1972). Klebsiella aerogenes has been reported to volatilize mercury (Magos et al., 1964). Microorganisms further carry the ability to form biofilms of single or multispecies bacteria. Biofilms provide a protective covering to the cohort of bacteria, protecting them from harsh conditions of the environment. From an industrial point of view, biofilm forming microorganisms are of much importance as they are extensively used in bioreactors to treat waste effluents, carry out heavy metal reduction

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and pollutant degradation. Anammoxis is another energy-saving technology and can efficiently treat industrial wastewater. In anammox bacteria, the catabolic reaction occurs inside the intracytoplasmic compartment called anammoxosome (Niftrik et al., 2004). Plastics are polymers of synthetic and semi-synthetic materials. Nowadays, biodegradable plastics (PHA and PHB) are also produced to eliminate environmental pollution (Witt et al., 1997). Recent studies found that plastics can be degraded by few microorganisms such as bacteria and fungi. Microorganisms use plastic as their nutrient source and breakdown the polymers to fulfill their carbon need for their metabolic activity. Rubber is also a synthetic material. The conventional way to manage rubber waste is to burn them producing hazardous gases like carbon monoxide and ultimately leading to air pollution. Biodegradation of rubber waste is a time taking process. There are few microorganisms present that may degrade rubber. Biological degradation follows few steps like-treatment with sulfur oxidizing/reducing bacteria (Pyrococcus furiosus) and devulcanizing with Thiobacillus ferrooxidans. After that rubber residues are easily degradable (Keri et al., 2008).

3.2 Municipal waste This category of waste includes household wastes, office building waste, garden and yard waste, market cleansing and street waste, etc. All these wastes are collected and treated by municipalities. During municipal wastewater treatment, sludge is produced as a byproduct. It can be used as fertilizer but also contains a large amount of pollutants. It can be stabilized by the process of composting where various microorganisms can degrade the organic matters under aerobic conditions into simpler less harmful forms. A harmful constituent of municipal and agricultural wastes are POPs. These are organic substances found in beauty products, surfactants, flame retardants, pesticides which can be biotransformed into toxic nondegradable forms. POPs can magnify over the food chain causing severe health threats and carcinogenic effects. With advances in research, microbial degradation of POPs is preferred over conventional methods owing to their enhanced efficiency, low cost, and reduced environmental impact. Herbicides such as Propanil generate a harmful substance called 3,4-dichloroaniline (3,4-DCA), which is difficult to degrade and hence pollutes soil as well as water waste (Call et al., 1987). Effective degradation of Propanil requires bacteria from nine different genera, immobilized on a support in a suitable bioreactor. Such microbial degradation of Propanil is complete and produces no harmful byproducts (Herrera-Gonza´lez et al., 2013). The Kani City of Japan has adopted the use of effective microorganism (EM) on the municipal level to treat the wastes. Later this model has been taken up by the EM Research Organization of Tucson, Arizona, and had encouraged the use of EM for municipal waste treatment across the USA.

3. Microorganisms for waste management

3.3 Agricultural wastes Agricultural waste like rice straw, wheat straw, soybean straw, sugarcane straw, and cotton stalks harm the environment in various ways. These wastes are often burned in the field and lead to the emission of harmful gases like CO2, NO2, CO, etc. contributing to air pollution. These are also dumped in various areas that lead to foul odor and may spread various diseases. The proper handling and decomposition of agricultural waste are of utmost importance to save the environment. Composting is an efficient way to decompose agricultural waste. Microbes and other organisms play an important role in decomposing the agricultural waste by the composting process. Among fungi, Aspergillus, Penicillium, Trichoderma are important from a decomposition point of view. Enzymes like hydrolases, amidases, and oxygenases are released by microorganisms which can catalyze the conversion of pesticides in less harmful form. White rot fungus Phanerochaete chrysosporium can produce peroxidases that can degrade pesticides like DDT and pesticide related compounds like dioxin (Bumpus and Aust, 1987). Agro-wastes are primarily composed of the cellulosic backbone with usually a high carbon content and possess different functional groups. Such properties have been found useful in waste effluent management, biogas, and biodiesel production, and biocatalyst fabrications (Yahya et al., 2015). Keratin forms a major component of agricultural and industrial waste in the form of keratinaceous byproducts. The conventional degradation of these products through chemical treatment results in the production of hazardous secondary pollutants. Several studies over the past decades have reported keratinase production by several microorganisms like bacteria and some fungi which can biologically degrade keratinaceous substrates. With the advances in protein chemistry, isolation of keratinases from specific microbes became possible enabling its application in poultry farm waste management, manufacture of ecofriendly fertilizers, cosmetic and pharmaceutical industries (Ghaffar et al., 2018).

3.4 Biomedical waste Biomedical wastes are toxic, hazardous, and can also be lethal as it can transmit many diseases. Biomedical wastes include wastes produced during diagnosis, human or animal treatment, and medical research activities conducted in hospitals and health camps. Proper disposal and management of biomedical wastes are of utmost importance to maintain a healthy environment. Conventionally, waste water effluents from hospitals and medical facilities are treated the same way as other general waste, which proves to be an inefficient approach to eliminate micropollutants from pharmaceuticals, bodily fluids, etc. (Joss et al., 2006). Biomedical wastes mainly contain large amounts of heavy metals and polycyclic aromatic compounds. Incineration, the practice of reducing the amount of waste by burning is regarded as conventional method for handling biomedical waste. A major limitation with incinerators is reckless landfilling of incinerator ash without proper treatment resulting in

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groundwater pollution and heavy metal contamination (Patil and Bohara, 2020). Biomedical waste management is multi-faceted and based upon integrated technologies to achieve an effective removal of pathogenic and toxic constituents. Microorganisms are an indispensable part of these technologies owing to their unique biological and chemical properties. Bacillus sp. KGMDI can grow in an area with a high concentration of heavy metals and can be used as a biological tool to reduce the negative impact of biomedical waste (Heera et al., 2014). Microbial-based biosynthesized nanoparticles are well characterized for their antimicrobial properties which are being exploited to treat and manage pathogens actively present in the biomedical waste. Owing to their high surface to volume ratio, nanoparticles possess the ability to catalyze heavy metal sequestration and reduction as well, making them an attractive alternative to conventional waste management technologies (Patil and Bohara, 2020). Being a constitutive part of waste treatment bioreactors like Membrane Bioreactors and activated sludge processes, microorganisms are utilized more directly in biomedical waste management (Patil and Bohara, 2020).

3.5 Radioactive waste Radioactive wastes includes wastes mainly from a nuclear reactor, hospitals, defense, research facilities, and fuel processing plants. These wastes are managed through geological disposal where the waste is placed safely deep underground. These repositories are constructed between 200 and 1000 m below the surface and wastes are placed there until the harmful radioactive substances get decayed. Scientists have found a way to speed up the decaying process in such a repository by using microorganisms. The reduction in the solubility rate of U(VI) to insoluble U(IV) is helpful to block its transport and can be a potent way of bioremediation of contaminated soils. The breakdown of uranium leads to the formation of soluble complexes with some organic molecules. These soluble forms of uranium can further be reduced by microorganisms to lesser harmful compounds. Microbial degradation in such a repository produces gases like methane, carbon dioxide, and hydrogen. These formed gases help to increase the rock cavity pressure of the repository and subsequently delay the movement of water-soluble radionuclides (Beaton et al., 2019). Bacteria like Proteobacteria and Cyanobacteria and algae including Haematococcus pluvialis are found in the fuel storage pond and are helpful to control the radionuclide fate of the pond (MeGraw et al., 2018). Bacteria like Clostridia and Geobacter are beneficial in intermediate-level radioactive waste degradation.

4. Microorganisms in environmental safety Microorganisms play a fundamental role in environmental safety. They show complex biogeochemical processes and the role of individual species is not clearly understood in many cases. Microorganisms mainly bacteria and fungi are extensively used for treating organic wastes as it can speed up the degradation process.

4. Microorganisms in environmental safety

Composting using cellulolytic microorganisms for the decomposition of lignocellulosic components is very useful (Leow et al., 2018). Direct disposal of wastes to landfills can be harmful to the environment by releasing greenhouse gases and also emits unpleasant odors. Composting is an alternative way to combat these problems (Al Zuahiri et al., 2015). Microorganisms are also helpful in converting organic waste into renewable biogas (Wang et al., 2011). Lignocellulose materials are abundantly present in biomass but their degradation rate is slower than other organic wastes. This creates an emerging need to improve lignocelluloses degradation technologies to optimize biomass utilization (Li et al., 2015). Such complex processes often require a consortium of a synthetically organized group of microorganisms (Puentes-Te´llez and Falcao Salles, 2018). The hydrolytic enzymes secreted by these microorganisms include cellulases, proteases, lipases, and amylases (Vargas-Garcia et al., 2010). The use of plastics and their products is ever increasing in industries, households and domestic appliances over the past decades. Most plastics are nonbiodegradable making their disposal a cumbersome and challenging, posing severe threats to environmental safety. Rapidly increasing plastic waste, lack of efficient management, and careless consumer behavior only aggravates the situation. Established degradation approaches rely on various chemical, thermal, physical, and biological processes. The biological degradation of polymers relies heavily on microbes with their ability to produce extracellular enzymes that act upon different polymers. Brevibacillus borstelensis is known to produce proteases that can digest such polymers (Hadad et al., 2005). Microorganisms stick to the surface of polymers and degrade them enzymatically into oligomers, dimers, and monomers which are eventually converted into CO2 and H2O upon mineralization. Several studies have shown that microbial enzymes increase the efficiency of polymer biodegradation and form an ecofriendly approach (Ahmed et al., 2018). It provides an industrially controlled biodegradative alternative for plastic waste management; fulfilling the void created by the high demands of plastics and poor disposal and management. The generation of bioelectricity from microbial fuel cells (MFCs) is very advantageous over conventional electricity generation technology (Kim et al., 2007) (Fig. 18.2). It has high conversion efficiency and shows safe performance (Rabaey and Verstraete, 2005). MFCs can potentially remove organic carbon matter from organic wastewater including biodiesel wastewater, brewery wastewater, human feces wastewater, household wastewater, etc. (Mohanakrishna et al., 2010). More advanced approaches like microbial electrolysis cell (MEC) for organic and inorganic waste degradation are gaining popularity. MEC utilizes exoelectrogenic microbes at the anode end and produces electricity by converting the organic matter from wastewater to gas (CO2) and protons. The released protons are then transferred to cathodes for the production of H2 (Rozendal et al., 2008). MEC alone is not sufficient to treat the wastewater but its integration with anaerobic digestion, membrane filtration, and anaerobic ammonia oxidation can meet the water reuse and discharge limits. The application of MEC in the urban wastewater treatment areas can potentially reduce the cost of wastewater treatment and sludge disposal.

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FIGURE 18.2 Microbial fuel cell. Figure adapted, with permission, from Zhang, Q., Hu, J., Lee, D-J., 2016. Microbial fuel cells as pollutant treatment units: research updates. Bioresour. Technol. https://doi.org/10.1016/j.biortech.2016.02.006 © 2016 Elsevier Ltd.

With the advent of industrialization and advances in technology, there has been an uphill demand for crude oil and products, petroleum, fossil fuels for energy production, product manufacture, and other diverse applications. The processes in excavation, refinement of fuels, and manufacture of their products require the intervention of chemicals, hydrocarbons, heavy metals, solvents which can have hazardous effects on environmental safety. Improper waste management of pollutants leads to their accumulation in soil, rivers, oceans, and other water bodies causing environmental deterioration. These substances are taken up by living organisms and undergo biomagnification along with the food chain eventually affecting various aquatic and terrestrial life forms (Valentı´n et al., 2013; Liu et al., 2017). Several reports suggest that conventional chemical processes used to clean up these pollutants have further detrimental effects (Jimoh and Lin, 2019). Recently, biosurfactant based bioremediation has gained attention in the scientific community as an ecofriendly alternative for waste management. Biosurfactants are biologically synthesized majorly via specific microorganisms and possess the unique property of reducing the surface tension between two liquids and influence changes in their surface interactions. These properties promise a significant role of biosurfactants in emulsification and deemulsification of oils, foam formation, and complex surface

5. Conclusion

chemistry of high value in industrial setups (Jimoh and Lin, 2019). Biosurfactants provide several advantages when compared to their chemical counterparts such as biocompatibility, biodegradability, nontoxicity, ecocompatibility, and broad range activity for longer periods (Pacwa-P1ociniczak et al., 2011; Mnif et al., 2014; Bezza and Nkhalambayausi Chirwa, 2015). According to some recent reviews, microorganism based production of biosurfactants is regarded as one of the hotspots for the growth of environmental safety and sustainability (Jimoh and Lin, 2019). Along with biosurfactants, microorganisms have recently evolved as efficient production factories of diversely important and relevant compounds. With rapid advances in recombinant DNA technology, protein biochemistry, genetic engineering, and biotechnology; it is now possible to direct the microorganisms toward the synthesis of the desired biomolecule or relevant compound such as specific enzymes, commercially important proteins, antibodies, cofactors, nanoparticles, etc. The biological synthesis of these entities allows for a better biocompatibility, biodegradability, ecological compatibility along with customized and controlled synthesis. Microbe-based bioproduction has emerged as an ecofriendly alternative to chemical and physical processes involving hazardous byproducts, toxic and corrosive reagents, and cumbersome methodologies. In this expanding industrialization era, global energy demands have reached an all-time peak. Nonrenewable fossil fuels like coal and petroleum are used all over the world in powerplants to generate electricity. The excavation, processing, and combustion of these fossil fuels result in the emission of greenhouse gases and harmful pollutants at a large scale causing both primary and secondary pollution. This creates an urgent need for greener and sustainable technologies to take ground.

5. Conclusion The environment consists of diverse microorganisms which can fulfill many purposes. Biological waste management is therefore indispensable for sustainable development. Microorganisms have been the solution for various problems that humankind has encountered in maintaining environmental quality. Microorganisms have the potential in waste management, biodegradation, environmental protection, biocomposting, bioleaching, nitrogen fixation, enhancing soil fertility etc. Though fossil fuel is limited, biofuel is renewable as well as low in cost. If we use biohydrogen as fuel, and it could be environmentally friendly and sustained economically too. Biohydrogen and electricity could team to provide attractive option in transportation and power generation. Microorganisms are responsible for enzymatic degradation of organic and inorganic pollutants providing effective means of pollution control. In an indirect way, microorganisms form the basis of diverse biogenic technologies that are comparatively “greener,” ecologically acceptable as well as equally effective to their other counterparts. Biogeochemical cycles are of utmost importance for the normal functioning of the ecosystem and maintenance of the environment.

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Enzymatic decolorization and degradation of azo dyes

19

Devikaben Bharatbhai Vishani, Anupama Shrivastav Department of Microbiology, Parul Institute of Applied Sciences, Parul University, Vadodara, Gujarat, India

1. Introduction Rapid industrial development has been resulted in large amount of wastes into the environment causing major pollution problem. Among many pollutants, textile industry effluent is the major source of environmental pollution. The textile industry daily discharge millions of litter untreated effluent in the form of waste water. The excessive discharge of the effluent from textile industries contain toxic chemicals such as azo dye and reactive dyes which adversely affect the nature resources, soil fertility and aquatic organisms and distribute the integrity of the ecosystem by the alters the pH, increase the biochemical oxygen demand and chemical oxygen demand, and greatly affect water quality. Discharge of effluents without removal of these dyes will remain in the environment and cause serious issues. Several physicochemical methods such as chemical treatment, adsorption, and ion-pair extractions have been used for azo dye decolorization but these methods are very expensive and product large amount of sludge after treatment. Therefor biological treatment methods are most suitable and widely used due to their cost effectiveness, ability to produce less sludge, and ecofriendly nature. In biological methods microorganisms such as bacteria, fungi, algae, and yeast are capable of degrading azo dyes under anaerobic and aerobic conditions. Although dye molecules display a high structure variety, they are degraded by few enzymes. These biocatalysts have one ordinary mechanistic feature. They are all redox-active molecules and thus, exhibit relatively wide substrate specificities. Suitable organisms excrete the active enzyme into the medium. The dye molecules are transport into the cells; another important requirement for this organism is its resistance against toxic effects of dyes and other components present in the effluent. This indicates that microorganisms may develop the ability of degrading azo component after an adaption period. Generally, the azo dye degradation by bacteria produced in two stages. The first stage involves reductive cleavage of the dyes azo dye linkages, resulting in the formation of generally colorless but potentially hazardous aromatic amines and

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second stage involves degradation of the aromatic amines. Bacterial biodegradation of aromatic amines is an almost exclusively aerobic process whereas, azo dye reduction usually requires anaerobic conditions.

2. Dyes Dyes are chemicals which bind to material and conduct color to that material. The color of a dye is due to the apperance of chromophore group. Dyes are widely used to color the compound like textile fiber, paper, leather, hair, fur, plastic material, wax, a cosmetic base and food stuff. Classification of dye based on chemical structure of chromophore there are 20e30 different groups of dyes. Azo such as monoazo, diazo, triazo, polyazo, anthraquinone, phthalocyanine, and triarylmethane dyes are the most important groups. The majority of industrial important azo dyes belong to the following classes: acid dyes, basic dyes, direct dyes, disperse dyes, mordant dyes, reactive dyes, and solvent dyes. The acid, basic, direct and reactive azo dye are ionic dyes. Dyes contain at least one nitrogenenitrogen double bond, however many different structures exist. In the azo dyes, monoazo dyes have only 1 N¼N bond, while diazo and triazo dyes contain two and 3 N¼N double bonds. The azo groups are normally connected to benzene and naphthalene rings. these side groups are necessary for communicate the color of the dye, with many different shades and avidity being possible. These dyes have different absorption spectrum and associated with electronic transition between molecular orbital. During dyeing process, a large amount of azo dye is lost in waste water. During dyeing processes 10%e15% of dyes were lost in effluent.

3. Azo dye Azo dyes are the largest class of synthetic aromatic dyes. Which is composed of one or more nitrogen double bonds and sulfonic group with lost of commercial interest. Azo dyes contain one, two, or three azo linkages, linking phenyl, naphthyl rings that are usually substituted with some functional groups including triazine amine, chloro, hydroxyl, methyl, nitro, and sulfonate. There are more than 3000 azo dyes which include Astrazon Red GTLN, Maxilon Blue GRL, and Sandolan Yellow are widely used by the textile, leather, cosmetics, food coloring, and paper industries. In the dyeing processes about 80% of azo dyes are used in textile industries. It had been estimated that approximately 10% of the dyes used in dyeing process do not bine to the fiber and are released into the environment. They possess toxicity like lethal effect, mutagenicity, carcinogenicity to plant and animal, and genotoxicity.

4. Classification of azo dyes

4. Classification of azo dyes Dyes are classified by two ways either according to their chemical structure or mode of application. The most importance system of classification of dyes is by chemical structure, which have many advantages. It readily identifies dyes as belonging to group that good all-around properties, like azo dyes and anthraquinone dyes. The major structure element responsible for light absorption in dye molecules is the chromophore group, such as a delocalized electron system with conjugated double bonds. Chromophores frequently contain heteroatoms as N, O, and S, with nonbonding electron. Common classes of dyes, based on the chromophore present, are discussed in the following sections.

4.1 Acid dyes The acid dyes usually in form of sodium slats of the color acid that contains sulfonic acid or phenolic group. These dyes very bright shades and comprise a wide range a wide range of fastness properties from very poor to very good. These dyes are mostly used to dye fibers having basic groups such as silk, wool, and polyamides. Application is generally made from under acid condition which caused protonation of the basic groups. The dyeing process may be represented as: Dyes þ Hþ þFiber/Dyes Hþ fiber

4.2 Basic or cationic dyes The basic or cationic dyes have basic amino group which is protonated under the acidic condition of the fibers by formation of salt linkages with anionic or acidic groups in the fibers. They generally knew for intense and brilliant shades but gives poor light fastness. The main applications of these dyes are dyeing on silk and wood fibers directly but not recommended on cotton.

4.3 Direct dyes The direct dyes are usually bearing sulfonic acid group when strong adsorbed on cellulose. However, these dyes are not considered as acid dyes because the sulfonic group are not used as a means of attachment to the fiber. These dyes are generally used for dyeing wool and silk fibers using a neutral bath. An example of direct dyes is Congo Red.

4.4 Mordant dyes Mordant dyes have poor affinity for the fiber. These dyes require a pretreatment of the fiber with a mordant material designed to bind the dyes. The mordent material

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attached to the fiber then combines with the dyes gives insoluble complex called lake. Dyes with mordant dyeing properties must contain groups, which can hold the metal in stable combination or chelate groups.

4.5 Vat dyes Vat dyes like sulfur dyes as they are insoluble but the reduced form of these dyes is soluble. These dyes are generally used in dyeing process. The reduced form of these dyes is generally used in dyeing process. The reduced form obtained by treating to compound with some reducing agent such as alkaline sodium hyposulfite in a large wooden vat, giving rise to the name vat dyes. The dyeing produced by vat dyes show good light and washing fastness properties as well as very affective in bleaching. Special method has been developed for the dyeing and printing of substrates other than cotton, e.g., wool, silk, and cellulose acetate.

4.6 Azoic dyes Azoic dyes are produced within the textile fibers by azo coupling. A numerous shade can be achieved by appropriate choice of diazo and coupling components. The usual process for development of azoic dyes shows the fiber is first impregnated with a solution of coupling component followed by the treatment with a solution of a diazonium compound. The dyed goods are soaped and rinsed. Sometimes, it is possible to apply both the diazo and the component parallel form aqueous dispersion and then to treat the goods with nitrous acid to produce the insoluble, bright and very fast azo dyes. application of azoic dyes are the dyeing and printing of cellulose fiber, especially cotton, giving shades of a high standard of fastness to wet and light processing.

4.7 Reactive dyes Reactive dyes are a new class of dyes that form covalent bonds with fibers processing hydroxyl or amino groups. An important type of reactive dyes has a chlorine atom, which reacts with the hydroxy group in the presence of base. Reactive dyes offer excellent rapidly to washing since the dye becomes a part of fiber.

4.8 Disperse dyes Disperse dyes are water insoluble dyes originally introduced for dyeing cellulose acetate and usually applied from fine aqueous dispersion. Disperse dyes molecules are generally small and some hydroxyl or amino group to give to give finite water solubility at dyeing temperatures. The main used of disperse dyes includes dyeing of cellulose acetate, nylon, polyester and polyester and polyacrylonitrile fibers. Most polyester fiber must be dyes under pressure or the used of organic swelling agent. The washing rapidly of disperse dyes of these fibers are excellent. The application of disperse dyes are includes dyeing woolen sheepskin and for surface dyeing of plastic.

6. Different method for the removal of dyes

4.9 Solvent dyes Solvent dyes contain no sulfo or other water-solubilizing groups. They are generally soluble in organic solvent. Solvent dyes are used in numerous manufacturing material such as stain, link, varnishes, lacquers, candle, polishes, copying papers, typewriter ribbons, soap, cosmetic, etc. tetrachloroethylene used of water is suitable dyeing processes for the dyeing of polyester fibers.

4.9.1 Properties of azo dyes Most of azo dyes are colored in their crystalline state and few of dyes are readily soluble in water in water while most dyes are partly soluble in water. The solubility of these dyes can be increased by the addition of organic solvents such as chloroform, cyclohexane, and DMF.

5. Strucutre of dyes Dyes are colored substance that is generally apply in aqueous solution because of its great affinity to water. The color of the dyes is contributing mainly by a chromophore group present in the chemical structure and is use in textile, paper, leather, or food industry. Synthetic dyes are normally made from petroleum byproducts and earth minerals. Different types of synthetic dyes use in textile industry. The azo dyes one is the most widespread dye class in the industry. They have one or more azo (N¼N) groups. Textile dyes are chemically diverse in nature and are broadly divided into azo, reactive, triphenylmethane, heterocyclic, polymeric structure. The synthetic dyes exhibit considerable structure diversity. The chemical classes of dyes employed more frequently on industrial scale are the azo anthraquinone, sulfur, indigoid, triphenylmethyl, and phthalocyanine derivatives. It should be noted that azoketohydrazone equilibria can be a vital factor in the easy breakdown of many of the azo dyes system. Some dyes reproduced in the review have only a minor importance from the point of view of industrial application.

6. Different method for the removal of dyes Textile industry is the key of dyes and hence the main source of water pollution, which risk of the aquatic as well as human life. There are various physical, chemical, and biological method for removal, but most convincing is adsorption due to its simplicity. However, implementation of physical/chemical method have the inherent drawbacks of being economically unfeasible (as they require more energy and chemicals), being unable to completely remove the recalcitrant azo dyes their organic metabolites, generating a significant amount of sludge that may cause secondary pollution problem, and involving complicated procedures.

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However, microbial or enzymatic decolorization and degradation is an ecofriendly cost-competitive alternative to chemical decomposition process that could help reduce water consumption compared to physicochemical treatment method.

6.1 Degradation methods of dyes

6.1.1 Physical and chemical method The conventional method used in the textile industry for the color removal from effluents include physiochemical method like coagulation, flocculation, and activated carbon adsorption. Both flocculation and adsorption generate large amounts of toxic sludge and waste, which required a separate treatment before disposal. However, this method involved. The physical methods, adsorption, and ion exchange have been most studied, adsorption methods have attracted considerable interest due to their higher efficiency for the removal of a wide range of dyes. The selection of an adsorbent is based on characteristics such as high affinity, capacity for target compound and the possibility of adsorbent regeneration. Although activated carbon is a very efficient adsorbent for various types of dyes, it is not used due to its high cost. Some researchers use low cost adsorbent material

6. Different method for the removal of dyes

like peat, bentonite clay, fly, ash, polymeric resins, ion exchangers, and many biological materials such as corn/maize cobs, maize stalks, and wheat straw for the color removal of dyes wastewater to make the process more economically feasible. However, the practical application of these adsorbents has been limited by problem associated with their regeneration or disposal, high sludge production, and low effectiveness with regard to a wide range of dyes and high cost. Filtration method such as nonfiltration, reverse osmosis and ultrafiltration have been used for water reuse and chemical recovery. In the textile industry, the use of membrane provides interesting possibilities for the separation of hydrolyzed dyestuffs and dyeing auxiliaries that simultaneously reduce the color, BOD, and COD of wastewater. With this approach, the selection of the types and porosity of the filter depends upon the chemical composition of the wastewater and the specific temperature required for the process. Membrane filtration is the method of water consumption and wasteful require treatment process. The processes that use membranes offer exciting possibilities for separation of dyestuff and dyeing auxiliaries that reduce simultaneously hydrolyzed color and biochemical oxygen demand/chemical oxygen demand of wastewater normally used to treat effluent reactive dye bath that could potentially reduce the volume of waste and recovery simultaneously salt. It can be separated into two or more components the flow of fluid to its molecular size. Advantages of this method is that it is fast, with low space requirement, and saturation can be reused. However, membranes have some significant drawbacks, including high investment costs, potential membrane fouling, and the production of secondary wasted streams, which need further treatment. Chemical oxidation method enables the destruction or decomposition of dyes molecules, such as ozone (O3), hydrogen peroxide (H2O2), and permanganate (MnO4). Modification in the chemical composition of a compound or a group of compounds take place in the present of these oxidizing agents, and thus the dye molecules become susceptible to degradation. Ozonation has been found to be effective due to its high reactivity with many azo dyes, the lack of alteration of the reaction volume due to its gaseous state and good color removal efficiencies. It is a very powerful and fast oxidizing agent that can react with most of chemical and with simple oxidizing agent ions, such as S-2, forming oxyanions such as SO3-2 and SO4-2. Ozone decolorizes water soluble dyestuffs, but with nonsuitable dye stuff react much slower. The waste water generated by the treatment of textiles normally includes other refractory components that ozone degradation required high pH in alkaline solution, ozone reacts almost inseparably to all present components, transforming organic compound smaller and more biodegradable molecules. Ozone therapy is used for mineralization. It is a relatively high cost processes with its short half-life. However, its short lifetime, ineffectiveness toward dispersed dyes and those insoluble in water, low COD removal capacity, as well as the high cost of ozone, limits the practical application of this technique.

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In advanced oxidation processes, oxidizing agents such as O3 and H2O2 or heterogenous photocatalysts are used with catalysts, such as Tio2, ZnO2, Mn, and Fe in the presence or absent of an irradiation source which generates (OH) radical for the destruction of hazardous dye pollutants.

6.2 Biologycal method Decolorization and degradation of azo dyes may take place by two method either adsorption on the microbial biomass (biosorption) or biodegradation of the dyes by the living cells. Biological treatment of textile azo dyes has been proved to be the best method due to its ability to degrade almost all dyes stuff and also overcome many disadvantages posed by the physiochemical processes. Biology treatment requires a large land area and limitation by sensitivity to the diurnal variation and toxicity some chemical and less flexibility in design and operation. Biological treatment is unable to obtain satisfactory color removal with current conventional biodegradation process. In addition, although many organic molecular degrade, many others are recalcitrant because of its complex chemical structure and organic synthetic to in particular, the nature of xenobiotics, the biodegradability of azo dyes is very limited. A wide range of microorganism are capable of degrading a variety of azo dyes including bacteria, fungi, actinomycetes, and yeast. They have developing enzyme systems for the decolorization and mineralization of azo dyes under certain environment conditions.

6.2.1 Bacterial degradation The bacterial reduction of azo dye is usually nonspecific and bacterial decolorization is normally faster. A wide range of aerobic and anaerobic bacterial such as bacillus subtilis, pseudomonas sp, Escherichia coli, Rhabdobacter sp, Enterococcus sp, Staphylococcus sp, Xenophilus sp, corneyrium sp Closterium sp, micrococcus sp, Acinetobacter sp, Geobacillus, lactobacillus, rhizobium, proteus sp, and klebsiella sp, have been extensively reported as degradation of azo dyes. some strains of aerobic use azo dyes as sole source of carbon and nitrogen, other only reduce the azo group by special oxygen-tolerant azo reductases. The ability of bacteria in metabolism of azo dyes has been investigated by number of research groups. Under aerobic condition azo dyes are not readily metabolized, though the ability of bacteria with specialized reductive enzymes to aerobically degrade certain azo dyes compounds. In contrast, many bacteria are anaerobic which reduces azo dyes by nonspecific, soluble, cytoplasmic reductase activity. Anerobic reductase of degrades of azo dyes may be convert into aromatic amine, which may be toxic, mutagenic, and prosily of carcinogenic for mammals. Therefore, in order to achieve complete degradation of azo dyes or azo compound this involves the aerobic biodegradation of the produce’s material.

6. Different method for the removal of dyes

6.2.2 Decortication by fungi Saccharomyces cerevisiae. The most studied of fungi with respect to the degradation of azo dyes are ligninolytic fungi that produce enzyme such as lignin peroxidase, manganese peroxidase, and laccase. There is much literature on the potential use of these fungi to oxidize phenolic, nonphenolic, soluble, and insoluble dyes. In contrast, manganese peroxidase has been reported as the main enzyme involved in color discoloration by phanerochaete chrysosporium and lignin peroxidase for Bjerkandera adusta. Some nonwhite-rot mushrooms that can successfully discolor dyes also reported by the researchers.

6.2.3 Decolorization of yeast In literature the ability of degrade azo dyes by yeast was only described in a few reports. In two first report described the use of Ascomycetes and Candida zeylanoides yeast, and the enzymatic system involved is present in a work with saccharomyces cerevisiae. isolation from contaminated soil to reduce model azo dyes. the characteristic of enzyme activity is described in further study with the yeast Issatchenkia occidentalis the enzymatic system involved is present in a work with saccharomyces cerevisiae.

6.2.4 Algae The living and nonliving algae have used in bioremediation of textile wastewater. The algae used for the degradation of azo dyes is mentioned in only few repots. the studies of algae that are involve in decolorization and degradation of azo dyes are blue green algae, green algae, and diatoms. Several species of chlorella (acuner and dilek) and Oscillatoria (Jinqi and houtian) were found to potent decolorization of azo dyes. Jinqi and houtian also state that some of the tested azo compound could be used as sole source of carbon and nitrogen by the algae. This could mean that algae play importance role in the removal of azo dyes and aromatic amines in stabilization ponds.

6.2.5 Enzymatic decolorization and degradation of azo dyes The primary step in bacterial decolorization of azo dyes, in aerobic and anaerobic conditions, the reduction of azo band is chromophore group. It may be involved various mechanism, such as enzyme, low molecular weight compound like 2, 20 azino-bis (3-ethylbenzothiazoline-6-sulfonic acid), chemically reduction by biogenic reductants like sulfide, or a combination of these and the location of these reaction may be either intracellular and extracellular sites. Enzymatic decolorization and degradation of azo dyes, are two enzymes females, i.e., azo reductases and laccases seem to have shown great potential. Laccase have great potential for decolorization of extensive range of industrial dyes. There is certain enzyme like peroxidase, polyphenol oxidase, lignin peroxidase, manganese, and so forth are also hopeful in the decolorization and degradation of azo dyes.

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7. Decolorization and degradation of azo dyes by azoreductase Azoreductase are the enzyme which catalyzed the reductive cleavage of azo band to produce colorless aromatic amine product. It requires low molecular weight reducing equivalent such as FADH and NADH as the electron donor in the form of a redox reaction. On the basis of coenzyme used this enzyme is of three types using NADH only or using both. Azoreductase can be cytoplasmic or membrane bound. The microbial azoreductase has great importance for designing the biotreatment procedure of wastewater containing azo dyes. In the last years, several azoreductase producing bacteria are reported by many researchers. Azoreductase have been identified and characterized from large number of bacteria, such as Staphylococcus aureus, Escherichia coli, Bacillus sp, Xenophilus azoreans, Pigmentiphaga kullae, and Rhodobacter sphaeroides. However, inclusion of intracellular azoreductase in bacterial decolorization has been in recent years because many azo dyes have complexes structure and high polarities. And it difficult for dyes to diffuse for cell membranes. A classification system for enzyme which is based on the secondary and tertiary amino acid analysis proposed by Abraham and john in 2007. The basic function and another classification system are used in which azoreductase are grouped as either flavin independent azoreductase and flavin dependent azoreductase. Although the azoreductase are reduce certain types of azo dyes. There are number of dyes that do not degrade efficiently. Still, the used of enzyme is advantageous according to substrate specificity and may be efficiently used textile water pretreatment. The enzyme cleaves azo bond (N¼N) and transfers four electrons as reducing equivalent. In each stage two electrons transfer to azo dyes that acts as an electron acceptor and cases decolorization by forming a colorless solution. Resulting the toxic aromatic amine which is late degrade by the aerobic process. Under anaerobic condition, azoreductase cell membrane use a redox meditator as a shuttle. This redox mediator dependent mechanism of membrane bond azoreductase is different from the mechanism of cytoplasmic azoreductase. Nonsulfonate azo dyes are mainly degrading by the soluble cytoplasmic azoreductase through the cell membrane. Thus, in aerobic condition enzyme come in contact to oxygen and redox mediator is reduce of the azo dyes. Occasionally, under unfavorable condition some cellulose enzyme may also get convert into dye degrading enzyme for example, flavin reductase from E. coli act as azoreductase.

7.1 Decolorization and degradation azo dyes by laccase Laccase enzyme degrade the azo dyes through a nonspecific free redial mechanism to from phenolic compounds and prevented by the formation of toxic aromatic amines. Laccase have been extensively studies of degradation of azo dyes. Laccase is a low molecular weight multicopper oxidase protein family enzyme that decolorization of azo dyes through a highly nonspecific free redial mechanism forming phenolic compounds. Laccase represent a family of copper containing polyphenol

8. Factor affecting dyes degradation by biological method

oxidase and normally called multicopper oxidase. Laccase’s friend discovered in of sap of the Japanese lacquer tree Rhus vernicifera, and its characteristic as a metal containing oxidase was discovered by Bertrand in 1985. It has great importance capacity and don’t used readily available oxygen as an electron acceptor. Several low molecular weight compound act as the efficient redox mediator in electron transfer step of laccase reaction. It is able to degrade and decoration phenolic compound and aromatic azo compounds. Several laccases producing fungi culture were reported for degradation of azo dyes. It degrades azo dyes using a highly nonspecific free radical-mediated mechanism and from of phenolic compound instead of a toxic aromatic compound. Laccase oxidized the phenolic ring using one electron to generate a phenoxy radical which is again oxidized by the enzyme to produce carbonium ion; 4-sulfophenyldiazene and benzoquinone get produced by the nucleophilic attack of water which are unstable in the presence of oxygen. Under aerobic condition sulfophenydiazene get oxidized to phenyldiazene radical. The later readily lose molecular nitrogen to producing a sulfiphenayl radial and ultimately producing sulfophenyl hydroperoxide, scavenged by oxygen.

8. Factor affecting dyes degradation by biological method The operation condition which affect the efficiency of microorganism to decolorized azo dyes are the present of salt. The level of aeration, pH, temperature and oxygen. Generally, a sodium concentration above 3000 ppm caused moderate inhibition of most bacterial activity. The azo dyes removal efficiencies under saline condition decreases. The ability of the bacterial cell to reduce dyes from a range of dyes classes mast be tested to determine the types of wastewater that can be treated by the system. The component might have been inhibitory effective on the dyes reducing process. The effect of these factor must be used investigation of biological method can be used to treat the industrial wastewater in color removal process.

8.1 pH The pH color removal is often at a neutral pH value or somewhat alkaline pH value. The color removal rapidly decreases at strongly alkaline pH value and strongly acid value. the color removal performance of the cell culture. Biological reduction of the azo band can result in an increase in the pH due to the formation of aromatic amine metabolites, which are more basic then the azo compound.

8.2 Temperature In many systems the rate color removal is increase with temperature increase the defined range that depend on the system. The color removal performance of the cell culture. The optimum cell culture growth temperature at 35e45 C. the color removal activity at high temperature can be attributed to the loss of cell viability or the denaturation of azo reductase enzyme.

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8.3 Oxygen The effect of oxygen on cell growth and dye reduction is the most importance factor to be considered. Oxygen have significant effect on the physiological characteristic of the cells during the cell reducing stage. If the extracellular environment is aerobic and its high redox potential electron acceptor. Oxygen, may inhibit the reduction mechanism. Because it is free from the oxidation of electron donors by the cell superior used to reduce oxygen rather than azo dyes and the reduction product water, is not a reductant. The azo dyes anion free redials form of the dyes, tend to be to oxidize again by molecular.

9. Mechanism of azo dyes Generally, the process of bacterial azo dyes biodegradation consists of two stages. The first step involves reductive cleavage of the azo bond the formation aromatic amine. And the second stage involves degradation of the aromatic amine under aerobic condition. The bacterial degradation of azo dyes either aerobic or anaerobic, is the reduction of the -N¼N- bond. This reduction may involve different mechanism. Such as redox mediator, and chemical reduction by reductants like sulfide or combination. This reaction involving enzyme mediated azo dyes reduction may be either specific or nonspecific. These azo dyes reduction mechanism have been shown to greatly accelerated by the addition of many redox mediating compounds, such as anthraquinone disulfonate (AQDS) and anthraquinone sulfide (AQS).

10. Conclusion Enzymatic processes are very promising for decolorization and degradation of azo dyes. The wastewater of dyes creates environmental pollution as well as medical and aesthetic problems. As regulation are becoming even more stringent, there is an urgent need for technically feasible and cost-effective treatment method. The selection of the best treatment option for the bioremediation of a specific types of industrial wastewater is difficult task because of the complex commotion of these effluents. Microbial and decolorization and degradation of azo dyes have a significant potential to address this problem due to their environmentally friendly, inexpensive nature, and also because they do not produce large quantities of sludge. To understand the decolorization and degradation mechanism of azo dyes, detailed information is needed about the initial enzymatic breakdown of azo linkage. The enzyme azoreductase system in bacteria is constitutive, inducible, or repressible. Therefore it could be important to new isolation of bacteria with high capabilities of degradation azo dyes. The problem of the total degradation of azo dyes recommended that the essential for more research.

Further reading

This literature review discusses that the aerobic and anaerobic biological method may be appropriate for the treatment of dye cottoning wastewater. Microorganism that used the dyes as a sole source of carbon, nitrogen, and energy are of special interest and significance because they consume the dye for their growth and activities while at the same time eliminate the pollutant in a real sense. Such microorganism is a valuable gift from nature.

Further reading Benkhaya, S., M’rabet, S., Harfi, A.E.I., 2020. Classifications, properties, recent synthesis and application of azo dyes. Heliyon 6, e03271. Chacko, J.T., Subramaniam, K., 2011. Enzymatic degradation of azo dyes e a review” e. Int. J. Environ. Sci. 1 (6). Devarkonda, P.S., Sai Vilas Reddy, P., Sri Devi, D.V., Sree Venkat, M., November, 2019. Microbial degradation of azo dyes from textile industry- review. Int. J. Eng. Res. Technol. 8 (11). Ganesh Saratale, R., Saratale, G.D., Chang, Jo -shu, Govindwar, S.P., 2011. Bacterial decolonization and degradation of azo dyes: a review. J. Taiwan Inst. Chem. Eng. 42, 138e157. Kannam, S., Dhandayuthapani, I., Sultana, M., 2013. Decolonization and degradation of azo due e ramazol black B by newly isolated Pseudomonas putida. Int. J. Curr. Microbiol. Appl. Sci. 2 (November 4), 108e116. Khalid, A., Arshad, M., Crowley, D., 2010. Bioaugmentation of Azo Dyes 9, 1e37. Kumar, P., Agnihotri, R., Wasewar, K l, 2012. Status of absorptive removal of dye from textile industry effluent. Desalinat. Water Treat. 50, 226e244. Lakhan Singh, R., Kumar Singh, P., Pratap Singh, R., 2015. Enzymatic decolonization and degradation of azo dyes- A review. Int. Biodeterior. Biodegrad. 104, 21e31. Mahmood, S., Khalid, K., Arshad, M., Mahmood, T., Crowley, E., February, 2015. “Detoxification of Azo Dyes by Bacterial Oxidoreductase Enzymes”- Critical Review in Biotechnology. Mojsov, K.D., Andronikov, D., Janevski, A., Kuzelov, A., Gaber, S., 2016. The Application of Enzymes for the Removal of Dyes from Textile Effluents, vol. 5, pp. 81e86, 1. Popli, S., Patel, U.D., 2015. Destruction of azo dyes by anaerobic- aerobic sequential biological treatment: a review. Int. J. Environ. Sci. Technol. 12, 405e420. Sandhya, S., 2010. Biodegradat. Azo Dyes Under Anaerob. Condit.: Role Azoreductase 9, 39e57. Saranraj, P., Manigandan, M., 2018. Enzymes involved in bacterial decolorization and degradation of textile azo dyes. Indo- Asian J. Multidisciplin. Res. 4 (1), 1369e1376. Sarkar, S., Banerjee, A., Halder, U., Biswas, B., Bandopadhyay, R., 2017. Degradation of Synthetic Azo Dyes of Textile Industry: A Sustainable Approach Using Microbial Enzymes, vol. 2, pp. 121e131. Shah, M.P., 2018. Azo dye removal technologies. Austin J. Biotechnol. Bioeng. 5 (1). Shanmugaraju, V., Chidambara Rajan, P., year- 2018. A review on decolonization of dye by micro e organisms. Int. J. Comprehen. Res. Biol. Sci. 5 (1), 10e29. Sharma, S., Saxena, R., Gaur, G., October, 2014. Study of removal techniques for azo dyes by biosorption: a Review. IOSR J. Appl. Chem. 7 (Issue 10 Ver, I), 06e21.

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Singh, P. K., Lakhan Singh R., Bio removal of azo dyes: Review. Int. J. Appl. Sci. Biotechnol. 5 (2), 108e126. Singh, K., kumar, P., Srivastava, R., January, 2017. An overview of textile dyes and their removal techniques: indian perspective. Pollut. Res. 36 (4), 790e797. Sudha, M., Saranya, A., Selvakumar, G., Sivakumar, N., 2014. microbial degradation of azo dues: a review. Int. J. Curr. Microbiology And. Appl. Sci. 3 (2), 670e690. Vimala, G., Jeyakumar, P., Devi, A., singh, A., Iyer, P., 2015. Axo dyr degrading bacteria from textile effluent. Int. J. Curr. Microbiol. Appl. Sci. 4 (7), 199e210. Zuleta Correa, A., Merino e Restrepo, Andre’s, Jimenez- Correa, Sara, HormazaAnuguano, A., Alonso Cardona- Gallo, S., 2016. Use of white root fungi in the degradation of azo dyes from the textile industry. Dyna 83 (198), 128e135.

CHAPTER

Azo dyes: a notorious class of water pollutant, and role of enzymes to decolorize and degrade them

20

Vivek Chauhan, Priya Gautam, Shamsher S. Kanwar Department of Biotechnology, Himachal Pradesh University, Summer Hill, Himachal Pradesh, India

1. Introduction Increment in the synthesis of chemicals has prompted the fabrication of a wide assortment of compounds, some of which are xenobiotic or constant in the biological system. Azo dyes (or synthetic dyes) belong to these type of compounds, and presence of the aromatic structure make them extremely stable and resistant to degradation. Because of the presence of electron-withdrawing groups, these molecules become electron-deficient upbringing detention of degradation (Zollinger, 1987). Owing to their resistance to oxidizing agents, light, and water, these dyes are hardly disrupted in the environment. These dyes are complex aromatic compounds, which are regularly utilized for fraternization of different substrates like leather, textiles, papers, printing leather, cosmetics industries, and so forth. They are sometimes intertwined with heavy metals on the auxiliary interface and are considered to have moderately bad outcomes on the surrounding environment due to their toxic and inhibitory nature (Kulla, 1981). Azo dyes considerably constitute around half of the portion of the total dyes synthesized. They are generated in amounts that surpass 7
105 tons per year. Azo dyes are described by the existence of one or more azo bonds (eN¼Ne) coupling between a diazonium compound and aniline, phenol or other aromatic compounds. A significant part, around 10%e15%, of the azo dyes is delivered as efluent into the open streams introducing ecotoxic risk (Prasad and Rao, 2013). It increases BOD, COD, and pH of the water body where released, and also when delivered into nature with no treatment, they can cause genuine contamination issues, diminishing water transparency, and thus, restraining the riddling of solar radiation and diminishing photosynthesis. Dye effluent contains a synthetic substance, including dye itself that might be poisonous, mutagenic, or cancer-causing to different microbiological and several aquatic creatures. The existence of dyes or their degraded items in water can likewise cause human health issues and disorders, for example, nausea, hemorrhage, ulceration of the skin, and mucous films and the existence of such mixed compounds additionally evolve Development in Wastewater Treatment Research and Processes. https://doi.org/10.1016/B978-0-323-85657-7.00019-5 Copyright © 2022 Elsevier Inc. All rights reserved.

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into extreme harm to the kidney, liver, brain, central nervous system, and reproductive system (Robinson et al., 2001). These dye effluents are the most obvious marker of water contamination since certain dyes are noticeable at a concentration as low as 0.005e1 mg/L. Many of the physicochemical treatments such as coagulation, ion exchange extraction, membrane filtration, adsorption, ozonation or flocculation are being used for the dye effluent treatment. Further, these procedures give rise to the formation of sludge, which also needs to be treated in the due course of time. Flocculation and coagulation are the two main sludge producing techniques. Regular natural wastewater treatment frameworks, like, activated sludges, chemical oxidation, and so forth are incapable in dye expulsion on the basis that higher atomic weight compounds; for example, dyes, are not easily degraded by microorganisms and can pass as it is without undergoing any modification in structure from any treatment system (Groff, 1993). Governmental rules related to the discharge of the color effluents are becoming strict and thus new processes to solve these environmental problems are required. One such technique in the advanced researches to solve this issue of degradation of the azo dyes is the enzymatic approach. Various enzymatic sources can be cast for the purpose which can either be bacterial, plant-based and fungal based or from other sources. The synergist activity of enzymes is amazingly effective and particular, compared to chemical catalysts because of higher reaction rates, lenient reaction conditions and more noteworthy stereospecificity. They can catalyze responses at moderately low temperatures and in the whole aqueous-phase pH range. Even though biocatalysts are broadly utilized in a diverse field, their job in tackling the environmental issues has been taken into consideration supremely (Novotny et al., 2001). The origin of the critical enzyme and its natural function alongside system conditions are found to have a huge effect on the general execution for pollutant expulsion. Enzymes from fungal sources have been concentrated fundamentally in the dye expulsion process however plant-based enzymes for the expulsion of poisons are less studied (Maximo and Costa-Ferreira, 2004). It has been recommended that the enzyme could oxidize the dye structure to shape the compound with lower atomic weight and less toxic in nature. Some of the most frequently used enzymes for dye degradation are azoreductases, laccase, oxidases, peroxidases including manganese peroxidase and lignin peroxidase (Moreira et al., 2001).

2. Enzyme-meditated decolorization and degradation of azo dye The enzymatic system shows great potential for dye degradation (Fig. 20.1). The foremost step in enzymatic degradation is aerobic, anaerobic, or sequential method and subsequently, reductional azo bond cleavage chromophore group and also these enzymes can act in both extracellular and intracellular ways on the dyes. The reductional cleavage involves processes like chemical reduction by biogenic reductants or

2. Enzyme-meditated decolorization and degradation of azo dye

FIGURE 20.1 Overview of different process used for dye degradation.

low molecular weight redox criteria. As enzymes are having a wide scope of substrate specificity, high viability, and easy immobilization in nature, they can be possibly utilized in dye effluent or azo dyes comprising sludge treatment. Presence of the substrate-specific nature of the enzymes, they can catalyze just the desired or the particular reactions to remove pollutants by transforming them to other products or by precipitation, and contrarily, being biodegradable, it causes negligible natural contamination (Singh et al., 2015). Enzymes can likewise change properties of the specified waste to make it more satisfactory for the treatment or help in changing waste material to better-quality products. Enzymes can likewise change properties of the specified waste to make it more satisfactory for the treatment or help in changing waste material to betterquality products. The process of enzymatic degradation is a bridge between chemical and biological methods of degradation and decoloration of azo dyes. Enzymatic treatment can be utilized as a pretreatment step to remove one or more compounds that can hinder with upcoming downstream treatment techniques (Gianfreda and Rao, 2004). There are many situations which suggest that the use of enzymes can show a very positive outcome like treatment of low-volume, highly concentrated wastewater, removal of specific chemicals from complex industrial waste, and so forth. Although the use of enzymes is expensive, if used on the regular basis for the degradation and discoloration purpose of azo dyes, they can also cut off the huge production cost of the physicochemical techniques. Also, the enzymes are utilized in the degradation process by being immobilization on a suitable matrix. There is a large number of azo dyes used in industries and being redirected into the environment causing hazardous effects (Table 20.1), which need to be treated with some of the specific degrading enzymes before or after dispersion into the environment.

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Table 20.1 Some commonly used azo dyes, application and their primary hazardous effects. Types of azo dye Malachite green

Reactive brilliant red

Disperse red 1 and disperse red 13 Congo red Acid violet 7

Application

Hazardous effect

References

Used as dye staff in silk, leather, and paper and controversially used as antimicrobial in aquaculture Used extensively in textile due to its attractive color and fast fixation capacity

Carcinogenesis, mutagenesis, chromosomal fractures, teratogenicity and respiratory toxicity Inhibit function of human serum albumin, cause alteration of function, may bind to body protein or enzyme Mutagenic, may affect the activity and composition of microbial communities

Srivastava et al. (2004)

Used as textile dye in industry

Used to dye cotton Used in paper, cosmetic, food, and especially in textile industries

Carcinogenic and mutagenic effect Chromosomal aberration, membrane lipid peroxidation

Li et al. (2010)

Ferraz et al. (2011)

Gopinath et al. (2009) Mansour et al. (2010)

The enzymatic degradation and decolorization of industrial dyes have dispute because of the huge assorted variety of chemical structures among the synthetic azo dyes, including polyenes compounds, azo, nitro, anthraquinones, and nitroso (Akhtar et al., 2005).

3. Mechanism of degradation and decolorization by peroxidases Peroxidases (E.C.1.11.1.7) are the hemoproteins or the heme-containing enzyme which can catalyze in the presence of hydrogen peroxide (H2O2). Heme is compounding intermediate between iron ion (Feþ3) and the molecule protoporphyrin IX. Heme Peroxidases are the pervasive type of enzymes present in approximately all the organisms and distributed broadly into plants, animals and microorganisms. Peroxidases are divided into three classes, out of which class II exhibiting fungal peroxidases have manganese peroxidase (MnP) and ligninases, or lignin peroxidase (LiP), which are useful in azo dye degradation and class III containing some of the plant peroxidases like turnip peroxidase (TP), horseradish peroxidase (HRP), soybean peroxidase (SBP) and bitter gourd peroxidase (BGP) showed visual effects in recent researches of azo dye degradation and decolorization (Koua et al., 2009).

3. Mechanism of degradation and decolorization by peroxidases

3.1 Manganese peroxidase MnP (EC 1.11.1.13) is fungal peroxidases and was firstly uncovered in Phanerochaete chrysosporium fungal species and later discovered to be produced by other fungal species of white-rot fungi. The mechanism of MnP involves the oxidation by hydrogen peroxide (H2O2) to the interposed compound manganous ions (Mnþ2) that again initiates the oxidation of Mnþ2 to Mnþ3. Oxalic acid-like organic acids stabilizes the chelated Mnþ3 and this Mnþ3 organic acid complex formed, is measured as an active oxidant. Hence, by this way, MnP oxidized its natural substrate i.e., lignin as well as the azo dyes (Hofrichter, 2002). Isoenzymes of MnP can be readily effective in discolouration of the dyes and phthalocyanine complexes in an Mnþ2 independent manner. Different MnPs can be used or can be obtained from variable sources showing vast numbers of applications (Table 20.2). Phlebia tremellosa culture medium showed discolouration in the presence of MnP when augmented with MnCl2 (Kirby et al., 2000). Some studies also reveal the decolorization of sulfonaphthalein (SP) at pH 4.0 by MnP from Pleurotus ostreatus. Alongside, the degradation of the azo dyes is also corresponding with the high MnP activity.

Table 20.2 MnP used for degradation of azo dyes. Source

Dye/effluent

Experimental conditions

References

Debaryomyces polymorphus, Candida tropicalis Lentinula edodes

RB 5

MnP from these fungi was responsible for decolorization of RB 5

Yang et al. (2003)

Dye decolorization was markedly decreased by the absence of manganic ions and H2O2

Boer et al. (2004)

Nematoloma frowardii

Brilliant cresyl blue and methylene blue (MB) Flame orange and ruby red

Pricelius et al. (2007)

Schizophyllum sp.

Congo red (CR), OG, orange IV

Dichomitus squalens

Azo and anthraquinone dyes

Pleurotus calyptratus

OG, RBBR

MnP N-demethylated these dyes and concomitantly polymerized them to some extent The azo dyes such as CR, OG and orange IV were efficiently decolorized by purified MnP The purified MnP was able to decolorize selected azo and anthraquinone dyes more rapidly than laccase. Within 14 days the strain decolorized up to 91% of OG and 85% of RBBR in liquid culture and more than 50% of these dyes on agar plates

Cheng et al. (2007) Xiao-Bin et al. (2007)

Eichlerova et al. (2006)

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3.2 Lignin peroxidase Lignin peroxidase (LiP) (EC 1.11.1.14) also known as ligninase is fungal peroxidase. It catalyzes the nonphenolic aromatic structures and also catalyzes some of the additional oxidations in the side chains of lignin. Different types of LiP can be extracted from variable sources and all may have variable applications (Table 20.3). LiP obtained from fungal species Bjerkandera adusta can be very effective in transforming six industrial azo and phthalocyanine dyes. According to the study reports of Pointing and Vrijmoed, LiP plays an important role in decolorization and transformation of the azo dyes (Pointing and Vrijmoed, 2000). LiP from Phanerochaete chrysosporium demonstrated that Procion Brilliant Blue HGR, Navidol Fast Black and Ranocid Fast Blue were catalyzed and showed transformation as well as decolorization. Phanerochaete chrysosporium originated fungal peroxidases, Crude LiP and MnP together highlighted decolorization of an industrial azo dye, Reactive Brilliant Red Ke2BP (Yu et al., 2006). Study reports of some of the scientists also stated that the peroxidase enzyme secreted from the Arundo donax, Phragmites australis and Typha angustifolia macrophytic plants have a specific role in the degradation purpose of the azo dyes like amido black and amaranth (Haddaji et al., 2015).

3.3 Horseradish peroxidase Industrially important types of azo dyes can be degraded as well as precipitated by the help of plant-derived peroxidases like HRP. They can successfully catalyze the degradation of these dyes. HRP shows a higher degree of affirmation toward Remazol Blue and Cibacron Red. Even though at neutral pH Remazol Blue can behave as a powerful confronting inhibitor of HRP however at pH more than 2.5, catalyst

Table 20.3 LiP used for degradation of azo dyes. Source

Dye/ effluent

Phanerochaete chrysosporium

MB and azure B

Pseudomonas desmolyticum NCIM 2112

Xylene cyanol, fuchsine

Acinetobacter calcoaceticus NCIM 2890

Reactive brilliant red Ke2BP

Experimental conditions

References

HRP was able to N-demethylate both dyes, but exhibited much slower reaction kinetics than LiP and required higher H2O2 concentrations Degradation of dyes by LiP coupled with glucose oxidase showed H2O2 supply strategy was effective for improvement of the efficiency of the decolorization of dyes. LiP decolorized a dye concentration of 60 mg/L and below to no less than 85

FerreiraLeitao et al. (2003) Lan et al. (2006)

Yu et al. (2006)

4. Mechanism of degradation and decolorization by laccase

FIGURE 20.2 Reaction mechanism of substrate substitution by HRP enzyme. HRP, HRP-I, and HRP-II depicts the presence of enzymes in their stable state, compound I in its first intermediate state, compound II in its second intermediate state severally, and AH2 and AH* are the oxidizing substrates present (Krainer and Glieder, 2015).

movement was found to be amazing. Immobilized HRP showed higher performance of an enzymatic activity in degrading dyes when compared to the free HRP in many dyes (Maddhinni et al., 2006). The functioning of the enzyme over the dye depends on the number of conditions such as dye and enzyme concentrations, pH, H2O2. Broad substrate specificity is shown by HRP for azo dyes degradation and decoloration purpose. The catalysis mechanism of HRP can be understood by the reaction equation present in Fig. 20.2.

4. Mechanism of degradation and decolorization by laccase Laccases (EC 1.10.3.2) these are the phenol oxidases and they bear the property to oxidize the substrate with oxygen reduction in water. They are capable to degrade aromatic, nonaromatic and xenobiotic compounds. These enzymes are the monomeric, dimeric or tetrameric type of glycoproteins with four numbers of copper atoms attached to each monomer at their catalytic site. Laccases have a higher power of bioremediation because they do not use freely available oxygen as an electron acceptor, do not show the requirement for any cofactor for the completion of degradation. For the electron transfer steps of the laccase enzyme mechanism low molecular mass compounds can be used which can act as the redox mediators (Telke et al., 2011). Laccase starts the degradation process with a nonspecific free radicalmediated mechanism to form the phenolic compounds despite the toxic ones, and further these substituted phenols are oxidized by the molecular oxygen used as an electron acceptor (Fig. 20.3). As mentioned, these dyes are copper oxidases and thus result in oxidization of the anthraquinone dyes with phenolic dyes. The starting of the reaction mechanism

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FIGURE 20.3 Mechanism of azo dyes degradation using laccase obtained from Pseudomonas sp. in and decoloration.

is with the deprotonation of the phenolic hydroxyl group. This deprotonation reaction will end with the further formation of unstable phenoxy radicals which straightens its way to quinone formation. In this complete process, the combination of the oxidative transformation takes place without the actual forming product’s coupling. The cleavage of oxidation heads toward product molecular mass reduction and also oxidative decarboxylation of different products formed (Polak and Jaroszwilkolazka, 2012). Laccase enzyme is produced by a variable number of organisms and has many originating sources (Table 20.4) bearing different types of the applications or the characters and thus helps degrade different types of azo dyes.

5. Mechanism of degradation and decolorization by azoreductases

Table 20.4 Laccase produced from different sources, their characteristics and dyes they degrade. Laccase producing organism Providencia sp. SRS82

Geobacillus stearothermophilus

Aeromonas sp. DH-6

Providencia rettgeri strain HSL1 and Pseudomonas sp. SUK1 Micrococcus luteus

Characters of the enzyme

Type of dye degraded

References

Intracellular and extracellular, intracellular respectively for lignin peroxidase and laccase Laccase removes an Hþ atom from the hydroxyl and amino groups of the ortho-and parasubstituted phenolic substrates and the aromatic amines Mg2þ, Mn2þ, and Ca2þ increase decolorization whereas Cu2þ, Zn2þ, Fe3þ and Cd2þ inhibit decolorization and Pb2þ and Naþ had no effect e

Acid black 210 tri azo dye

Agrawal et al. (2014)

Indigo carmine, congo red, remazol brilliant blue R (RBBR), brilliant green

Mehta et al. (2016)

Methyl orange (MO)

Du et al. (2015)

C.I. reactive blue 172 (RB172)

Lade et al. (2015)

Azo dyes

Kanagaraj et al. (2015)

e

5. Mechanism of degradation and decolorization by azoreductases These types of enzymes are present in large species of microorganisms bearing diverse functions as well as present with diverse shapes. These are the flavoenzymes also found in the higher eukaryotes. These are foremost the most active type of enzymes used for the azo dye’s degradation and decolorization mechanism. It is a reducing type of enzymes that can convert the azo dyes into colorless amines through the process of reductional cleavage of azo dyes. They also perform the function of detoxification and biotransformation of the azo dyes. As these enzymes are obtained from different sources, they show a wide difference in their catalytic activity, biophysical characteristics and cofactor requirement (Morrison et al., 2012). They can catalyze the chemical reaction in certain circumstances like under the

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presence of several specific reducing agents or cofactors such as NADH, NADPH, and FADH2. These reducing agents have the property to act as an electron donor and initiate the breakdown process of azo dyes. Along with these properties, the redox mediators are used as an electron shuttle. Azoreductases can be purified, isolated and can be biochemically characterized from different sources and source microbes being aerobic and anaerobic, and every enzyme extracted from variable sources has the variable requirement and functioning like cofactor requirement, biophysical characteristics and catalytic activity. Their classification was primarily done on a secondary and tertiary structure basis depending on their amino acid sequences. However, because of the presence of a very low level of homology in the sequence a new classification system is used, classified based on cofactor requirement or oxygen tolerance, mainly their flavin and NADH-dependence. However, the gene sequence and structures of aerobic and anaerobic azoreductases diversity seem to be distinct (Abraham and John, 2007). Thus, in accordance with the oxygen tolerance, these azoreductases classification can be done into two major categories which are oxygen-sensitive and oxygen-insensitive azoreductases. Burger and Stolz used Xenophilus azovorans KF46F to characterize the flavin-free oxygen-tolerant azoreductases and efficiently presented a three-group classification system based on a cofactor. Alkaliphilic and neutrophilic bacterial strains were used for the characterization and isolation of azoreductases which are NAD(P)H-dependent and are flavin-free in the medium (Misal et al., 2015). Reduction of all the azo dyes through azoreductases dependent on NAD(P)H forms the amines corresponding to them, helping in the breaking down of the azo linkages (eN]Ne), which finally results in the degradation of the azo dyes. Isolation of NADH and NADPH-dependent, flavin-containing azoreductases, was done from S. aureus (Azo1) and Enterococcus faecalis (AzoA). Azoreductases which are flavin free in nature initially lose their flavin-binding domain nature due to the mutational changes. When flavin nucleotide-binding domains are aligned in the gene sequence alignment they show a very highly conserved domain. All the types of azoreductases show specificity for substrates. Geobacillus stearothermophilus strain synthesized flavincontaining NADH-dependent azoreductases have less activity for Orange II than Acid red 88. Pseudomonas KF46 originated NAD(P)H-dependent azoreductases have a great activity for Orange I than Orange II. Flavin-free type of NADH azoreductases has many efficient substrates suitable like Orange I, and Orange II and Amaranth azo dyes. Similarly, many different compounds like 2-nitrophenol, 2nitro-benzaldehyde, 4-nitrobenzoic acid, and 3-nitrophenol showed great efficiency by showing reduction through flavin-free azoreductases. Depending on the functioning basis, azoreductases are classified as flavin-dependent and flavin independent azoreductases (Table 20.5). The azoreductases dependent on flavin cofactor and nicotinamide dependence or preference, have five subcategories; NADHdependent enzyme, NADPH-dependent enzyme, NADH and NADPH both used as coenzymes providing reductional energy for azo dyes reduction for degradation and decolorization purpose, flavin-containing NAD(P)H-dependent quinone oxidoreductases, flavin free NAD(P)H-dependent azoreductases (Qi et al., 2017).

5. Mechanism of degradation and decolorization by azoreductases

Table 20.5 Azoreductases produced from different sources, their characteristics and types of dyes they degrade. Azoreductases producing organism Shewanella sp. IFN4

Pseudomonas entomophila BS1

Alishewanella sp. Strain KMK6 Providencia sp. SRS82

Aeromonas sp. DH-6

Enterobacter sp. SXCR

Characters of the enzyme

Type of dye degraded

Wide range of substrate specificity (maximum enzyme activity showed with reactive black 5 as a substrate) activity stimulated by the addition of flavin or quinine compounds (M.W.d330.5 kDa) Flavin mononucleotidedependent activity and require NADH for its activity NADH-dependent azoreductases show reduction in COD (28%) Intracellular and extracellular, intracellular respectively for lignin peroxidase and laccase Mg2þ, Mn2þ and Ca2þ increase decolorization whereas Cu2þ, Zn2þ, Fe3þ and Cd2þ inhibit decolorization and Pb2þ and Naþ had no effect

Reactive black 5, acid red 88, direct red 81, acid yellow 19 and disperse orange 3

Imran et al. (2016)

Reactive black 5

Khan and Abdul (2015)

More in reactive blue 59 as compared to golden yellow HER Acid black 210 tri azo dye

Kolekar et al. (2013)

Methyl orange (MO)

Du et al. (2015)

Sulfonated azo dye (Congo red)

Prasad and Aikat (2014)

References

Agrawal et al. (2014)

P. aeruginosa organism showed the possible activity of the NAD(P)H quinone oxidoreductase and illustrated that these belong to the same FMN-dependent azoreductases superfamily. This enzyme shows the great potential to cleave the azo bond linkage and gives the four reducing equivalent electrons. In every step of the reduction process two reducing equivalent electrons shifts to the azo dye side acting as an electron acceptor, by this step the dyes start to decolorize by the formation of colorless solution. This step results in the formation of toxic aromatic amine intermediate which can further be degraded by the aerobic processes (Fig. 20.4). Nonsulfonated azo dyes can be degraded through the soluble cytoplasmic azoreductases. Being an oxygen-sensitive enzyme anaerobic degradation is more

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FIGURE 20.4 Mechanism of azo dyes degradation using azoreductases.

efficient than aerobic degradation (Russ et al., 2000). Redox mediator reduction takes place in the aerobic conditions, for example, if E. coli originated flavin reductase acts as azoreductases, it uses FADH as a redox mediator. These azoreductases can be used successfully in the azo dye degradation because of the properties like aerobic and anaerobic enzyme activity, kinetic properties and substrate specificities, temperature, optimal pH, and thermal stability (Lima et al., 2014).

6. Conclusion Azo dyes comprise the biggest and most flexible class of synthetic dyes utilized in an assortment of fabrication including material, drug, food, and beautifiers enterprises. The presence of these dyes gives extraordinary color to effluents which prompt environmental issues. The choice of the best treatment alternative for the bioremediation of these dyes is a troublesome assignment due to the complex arrangement. Microbial and enzymatic decolorization and debasement of azo dyes can deliver this issue because of their ecological well disposed of, cheap nature and in light of the fact that they don’t deliver huge amounts of effluentsdthus, enzymes and enzymatic processes. Enzymatic measures are extremely positive for the disruption of synthetic azo dyes. The pathways of azoreductase, laccase, and peroxidase for degradation of azo colors have been considered in the review giving the basic idea of the complete degradation process of azo dyes. Azoreductases are enzyme gatherings, communicated in azo dyes debasing microorganisms for azo dye decolorization and degradation. These enzymes catalyze the response just in presence of diminishing operators like NADPH, NADH and FADH2. Laccases are the most basic

References

individuals from the multicopper oxidase protein family. These are oxidoreductases that have extraordinary significance in bioremediation wonder. At last, peroxidases are conjugated protein types of enzymes which in presence of H2O2 can catalyze the response. Thus, after this discussion, it is very much clear that microbial enzymes can be positively used in defeating the prevailing of this azo dye degradation and decolorization.

Acknowledgments This work has been funded by Council for Scientific and Industrial Research, New Delhi. The authors are thankful to CSIR, New Delhi as well as DBT, New Delhi for continuous financial support to the Department of Biotechnology, Himachal Pradesh University, Shimla (India).

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Gopinath, K.P., Murugesan, S., Abraham, J., et al., 2009. Bacillus sp. mutant for improved biodegradation of Congo red: random mutagenesis approach. Bioresour. Technol. 100 (24), 6295e6300. Groff, K.A., 1993. Textile waste. Water Environ. Res. 65, 421e425. Haddaji, B., Bousselmi, L., Saadani, O., Nouairi, I., Gharabi-Gammar, Z., 2015. Enzymatic degradation of azo dyes using macrophytic species Arundo donax, Typha angustifolia and Phragmites australis. Desaline Water Treatment 53, 1129e1138. Hofrichter, M., 2002. Review: lignin conversion by manganese peroxidase (MnP). Enzym. Microb. Technol. 30, 454e466. Imran, M., Negm, F., Hussain, S., et al., 2016. Characterization and purification of membranebound azoreductase from azo dye degrading Shewanella sp. strain IFN4. Clean 44 (11), 1523e1530. Kanagaraj, J., Senthilvelan, T., Panda, R.C., 2015. Degradation of azo dyes by laccase: biological method to reduce pollution load in dye wastewater. Clean Technol. Environ. Policy 17 (6), 1443e1456. Khan, S., Abdul, M., 2015. Degradation of Reactive Black 5 dye by a newly isolated bacterium Pseudomonas entomophila BS1. Can. J. Microbiol. 62 (3), 220e232. Kirby, N., Merchant, R., McMullan, G., 2000. Decolorization of synthetic textile dyes by Phlebia tremellosa. FEMS Microbiol. Lett. 188, 93e96. Kolekar, Y.M., Konde, P.D., Markad, V.L., et al., 2013. Effective bioremoval and detoxification of textile dye mixture by Alishewanella sp. KMK6. Appl. Microbiol. Biotechnol. 97 (2), 881e889. Koua, D., Cerutti, L., Falquet, L., Sigrict, C.J., Theiler, G., Hulo, N., Dunand, C., 2009. PeroxiBase: a database with new tool for peroxidase family classification. Nuclear Acid Res. 37, 261e267. Krainer, F.W., Glieder, A., 2015. An updated view on horseradish peroxidases: recombinant production and biotechnological applications. Appl. Microbiol. Biotechnol. 99 (4), 1611e1625. Kulla, H.G., 1981. Aerobic bacterial decolorization of azo dye. FEMS Microbiol. Lett. 12, 387e399. Lade, H., Kadam, A., Paul, D., et al., 2015. Biodegradation and detoxification of textile azo dyes by bacterial consortium under sequential microaerophilic/aerobic processes. EXCLI J 14, 158. Lan, J., Huang, X., Hu, M., Li, Y., Qu, Y., Gao, P., Wu, D., 2006. High efficient degradation of dyes with lignin peroxidase coupled with glucose oxidase. J. Biotechnol. 123, 483e490. Li, W.Y., Chen, F.F., Wang, S.L., 2010. Binding of reactive brilliant red to human serum albumin: insights into the molecular toxicity of sulfonic azo dyes. Protein Pept. Lett. 17 (5), 621e629. Lima, D.R., Baeta, B.E., Silva, G.A.D., et al., 2014. Use of multivariate experimental designs for optimizing the reductive degradation of an azo dye in the presence of redox mediators. Quı´m. Nova 37 (5), 827e832. Maddhinni, V.L., Vurimindi, H.B., Yerramilli, A., 2006. Degradation of azo dye with horseradish peroxidase (HRP). J. Indian Inst. Sci. 86, 507e514. Mansour, H.B., Ayed-Ajmi, Y., Mosrati, R., et al., 2010. Acid violet 7 and its biodegradation products induce chromosome aberrations, lipid peroxidation, and cholinesterase inhibition in mouse bone marrow. Environ. Sci. Pollut. Res. 17 (7), 1371e1378.

References

Maximo, C., Costa-Ferreira, M., 2004. Decolorization of reactive textile dyes by Irpex lacteus and lignin modifying enzymes. Process Biochem. 39, 1415e1419. Mehta, R., Singhal, P., Singh, H., et al., 2016. Insight into thermophiles and their widespectrum applications. 3 Biotech 6 (1), 1e9. Misal, S.A., Humne, V.T., Lokhande, P.D., Gawai, K.R., 2015. Biotransformation of nitro aromatic compounds by flavin-free NADH-azoreductase. J. Biorem. Biodegrad. 6, 2e6. Moreira, M.T., Palma, C., Mielgo, I., Feijoo, G., Lema, J.M., 2001. In vitro degradation of polymeric dye (poly R-478) by manganese peroxidase. Biotechnol. Bioeng. 75, 362e368. Morrison, J.M., Wright, C.M., John, G.H., 2012. Identification, Isolation and characterization of a novel azoreductase from Clostridium perfringens. Anaerobe 18, 229e234. Novotny, C., Rawal, B., Bhatt, M., Patel, M., Susek, V., Molutoris, H.P., 2001. Irpex lactless and Pleatotus ostreatus for decolorization of chemically different dyes. J. Biotechnol. 89, 113e122. Pointing, S.B., Vrijmoed, L.L.P., 2000. Decolorization of azo and triphenylmethane dyes by Pycnoporus sanguineus producing laccase as the sole phenoloxidase. World J. Microbiol. Biotechnol. 16, 317e331. Polak, J., Jarosz-wilkolazka, A., 2012. Fungal laccases as green catalysts for dye synthesis. Process Biochem. 47, 1295e1307. Prasad, S.S., Aikat, K., 2014. Study of bio-degradation and bio decolourization of azo dye by Enterobacter sp. SXCR Environ. Technol. 35 (8), 956e996. Prasad, A.S.A., Rao, K.V.B., 2013. Aerobic biodegradation of azo dyes Bacillus cohnii MTCC 3616: an obligately alkaliphilic bacterium and toxicity evaluation of metabolites by different bioassay systems. Appl. Microbiol. Biotechnol. 97, 7469e7481. Pricelius, S., Held, C., Sollner, S., Deller, S., Murkovic, M., Ullrich, R., Hofrichter, M., Cavaco-Paulo, A., Macheroux, P., Guebitz, G.M., 2007. Enzymatic reduction and oxidation of fibrebound azo-dyes. Enzym. Microb. Technol. 40, 1732e1738. Qi, J., Anke, M.K., Szymanska, K., Tischler, D., 2017. Immobilization of Rhodococcus opacus 1CP azoreductase to obtain azo dye degrading biocatalysts operative at acidic pH. Int. Biodeterior. Biodegrad. 118, 89e94. Robinson, T., McMullan, G., Marchant, R., Nigam, P., 2001. Remediation of dyes in textile effluents: a critical review on current treatment technologies with a proposed alternative. Bioresour. Technol. 77, 247e325. Russ, R., Rau, J., Stolz, A., 2000. The function of cytoplasmic flavin reductases in the reduction of azo dyes by bacteria. Appl. Environ. Microbiol. 66 (4), 1429e1434. Singh, R.L., Singh, P.K., Singh, R.P., 2015. Enzymatic decolorization and degradation of azo dyesda review. Int. Biodeterior. Biodegrad. 104, 21e31, 6. Singh RL, Khanna SK, Singh GB (1988) Acute. Srivastava, S., Sinha, R., Roy, D., 2004. Toxicological effects of malachite green. Aquat. Toxicol. 66 (3), 319e329. Telke, A.A., Ghodake, G.S., Kalyani, D.C., Dhanve, R., Govinder, S.P., 2011. Biochemical characteristics of textile dye degrading extracellular laccase from a Bacillus sp. ADR. Biores. Technol. 102, 1752e1756. Xiao-Bin, C., Jia, R., Li, P.S., Zhu, Q., Tu, S.Q., Tang, W.Z., 2007. Studies on the properties and co-immobilization of manganese peroxidase. Chin. J. Biotechnol. 23, 90e95.

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Yang, Q.X., Yang, M., Pritsch, K., Yediler, A., Hagn, A., Schloter, M., Kettrup, A., 2003. Decolorization of synthetic dyes and production of manganese-dependent peroxidase by new fungal isolates. Biotechnol. Lett. 25, 709e711. Yu, G., Wen, X., Li, R., Qian, Y., 2006. In vitro degradation of a reactive azo dye by crude ligninolytic enzymes from nonimmersed liquid culture of Phanerochaete chrysosporium. Process Biochem. 41, 1987e1993. Zollinger, H., 1987. Color Chemistry: Syntheses, Properties and Applications of Organic Dyes and Pigments. VCH Publishers, Weinheim.

CHAPTER

Biofilm mediated bioremediation and other applications

21

Rajalakshmi Sridharan, Veena Gayathri Krishnaswamy Department of Biotechnology Stella Maris College (Autonomous), Affiliated to University of Madras, Chennai, Tamil Nadu, India

1. Introduction Biofilms, a group of self-aggregating microorganisms attaching on the solid surfaces in the environment. The surface of attachment ranges from the soil, colloids, living organisms surface, pipes, and medical equipments. The biofilm formation requires nearly 109 to 1011 cells/mL (Characklis, 1990). The highly versatile and resistant character of the biofilm require nutrients in minimum quantity. The matrix formed contain proteins, exopolysaccharides (EPS), and water (w95%). The attachment to the hydrophobic surfaces is achieved by using surfactants in EPS produced by itself. The matured biofilm transports nutrients, electron acceptors, and water molecules via the channels formed within the biofilm concerning time (Luthy et al., 1994; Seo et al., 2009). The communicative ability of the individual microbe in the biofilm increases the chances of horizontal gene transfer. Quorum sensing (QS) is a method for cell-cell communication involving auto inducers (AIs). The AIs binds to the bacterial surface receptors and initiates the gene expression thereby activating traits controlled by the relevant gene (virulence, sporulation) (Li and Tian, 2012). Acylhomoserine lactone (AHL), the most common class of AIs found in Gram-negative bacteria. The signaling involves HomoSerine Lactone moiety, acyl side chains, and a substitutional group (simple acyl, 3-hydroxylacyl or 3-oxoacyl groups). The AHL produced by the Lux1 proteins and they combine to control the expression of the gene. The AIs 2 known as “universal language” aids in communication between Gram-negative and Gram-positive bacteria. It allows inter- and intraspecies communication. AIs 2 is a product of S-adenosylmethionine detoxification. The AI 2 signaling happens at transduction level. The QS inhibitors inhibits the generation of AIs. Enzymes such as AHL lactonases, decarboxylases, metalobeta lactamases inhibits the QS (Zhang and Li, 2016). This develops a diverse group containing both aerobic/anaerobic microorganisms enabling it to grow in adverse conditions (Boles et al., 2004). The biofilm formation follows a cycle as illustrated in Fig. 21.1. The dipole-dipole interaction (van der Waals) initiates attraction between the surfaces and the microbes. The EPS production gives rise to the electrostatic interaction

Development in Wastewater Treatment Research and Processes. https://doi.org/10.1016/B978-0-323-85657-7.00018-3 Copyright © 2022 Elsevier Inc. All rights reserved.

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FIGURE 21.1 Cycle of biofilm formation.

as the cell wall of bacteria is either positively or negatively charged (James, 1991). EPS also contributes resistance to stress, extreme environmental changes and antimicrobial substances (Costerton et al., 1987).

2. Biofilms in bioremediation The biofilms involve diverse microorganisms producing different enzymes with specific metabolic pathways. The resistivity of biofilms to physical, chemical and biological agents adds to its advantage in treating pollutants in adverse environments within a short period. The ability to gene transfer with differential expressions based on the adaptation to the local environment leads to diverse metabolic pathways (Pratt and Kolter, 1999). The removal of pollutants is initiated by absorption, immobilization and degradation. The increase in heavy metals in aquatic environments leads to increased biofilm formation as it acts as a marker for pollution (Fuchs et al., 1997). The self-immobilization of the biofilm in the EPS produced by it neglects the immobilization process and matrix requirement for degradation enhancement. The biofilm with multi-species in proximity increases the gene expression of the metabolic pathway (Møller et al., 1998). The involvement of rhlQS in catechol, phenol, benzoate and other hydrocarbons metabolism in P. aeruginosa is reported. This provided the very first proof of QS regulated metabolism (Huang et al., 2013). In general, the nutrient distribution decreases toward the depth and metabolites produced by one microbe is utilized by another (Stewart and Franklin, 2008). The EPS produced by biofilm has wide environmental applications. The EPS produced by Halomonas sp., Enterobacter sp., Gordonia sp., Bacillus sp., Pseudomonas sp., Xanthomonas sp., emulsifies the pollutants (Ta-Chen et al., 2008). Plastic degradation using biofilm extended to be a better solution compared to the individual strains. Tribedi and Sil (2013) reported LDPE degradation by biofilm consisting of Pseudomonas sp. AKS2. Fig. 21.2 summarizes the steps involved in biofilm formation on pollutants.

3. Bioreactors in biofilm formation

FIGURE 21.2 Cascade of events in biofilm formation on pollutants.

3. Bioreactors in biofilm formation The application of fluidized bed reactor for nitro compounds (two to four dinitrotoluene and two to six dinitrotoluene) degradation using biofilm resulted in nearly 90% removal (Lendenmann et al., 1998). The in situ application of naturally biofilmforming microbes in the remediation of pollutants requires enhancement in nutrients, oxygen and microbial species. The bioaugmentation and biostimulation might initiate biofilm formation and enhance degradation (Mitra and Suman, 2016). The development of biofilm is aided using an optimum and controlled environmental conditions. The removal of pollutants by biofilm using bioreactors is discussed in Table 21.1.

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Table 21.1 Summary of bioreactors using biofilm in heavy metal remediation. Reactor type

Pollutants treated

References

Hydrogen based membrane biofilm reactor Hollow fiber membrane biofilm bioreactor Packed bed biofilm reactor

Nitro compounds and chloroform Toluene

Ziv-El and Rittmann (2009) Kumar et al. (2010)

Sequencing batch biofilm reactor

Phenanthrene and pyrene Phenolic compounds

Rotating Biological Reactor

Cu, Zn and Cd

Sequential anaerobic-aerobic movingbed biofilm reactor

Municipal solid wastes

Guieysse et al. (2000) Farabegoli et al. (2008) Costley and Wallis (2001) Chen et al. (2006)

4. Biofilm mediated remediation The endogenous microbes lacking the ability to degrade the pollutants requires ex situ process involving bioreactors. The biofilm with wide application in heavy metals, hydrocarbons, industrial wastewater remediation offers a better alternative to conventional method. The advantages of biofilm reactor includes increased biomass retention period, increased metabolism, and minimal inhibition of physical and chemical factors. Types of biofilm bioreactors used in remediation of pollutants includes stirred tank bioreactor, batch bioreactor, air-lift bioreactor, upflow anaerobic sludge blanket bioreactor, fluidized bed bioreactor, and air-lift suspension blanket bioreactor (Mitra and Mukhopadhyay, 2016). The heavy metal pollution in the environment cannot be treated as other contaminants. The removal of heavy metals is nearly not possible. Despite its rigidness, the conversion of heavy metals using microbes by oxidation or reduction decreases its toxicity. Immobilization increases the bioavailability of the heavy metals and biofilm makes it easy with EPS produced by it. The adsorption and desorption of the biofilm decide the fate of the pollutants. Costley and Wallis (2001), studied the removal of Cu, Zn, and Cd using biofilm by sorption/immobilization and desorption process. The sorption-desorption cycles showed repopulation of biofilm after desorption. Application of biofilm in wastewater containing organic and inorganic pollutants attracted many researchers. The process is made effective by taking disadvantages as an advantage which requires regular monitoring. The enzyme produced by the biofilms enhances the degradation as the structure of the matrix optimizes the absorption, bioavailability and coexistence of diverse microbes (Burmølle et al., 2014). The EPS of biofilm further chelates the heavy metal pollutants. The biofilm-forming microbial isolates tolerate nearly 2000 mg/L of heavy

5. Marine biofilms

Table 21.2 Pollutants degradation by biofilmdan overview. Pollutant degraded 3,4dichloroaniline (3,4-DCA) Nitrile degradation in wastewater Wastewater removal Greywater removal Phenol degradation

Biofilm used

References

Comamonastestosteroni WDL7-RFP

Horemans et al. (2017)

Recombinant Bacillus subtilis N4 - nitrilase gene (nit) from Rhodococcusrhodochrous BX2

Li et al. (2016)

Algae biofilm microbial fuel cell (ABMFC)

Yang et al. (2018) Zheng et al. (2020)

Biofilm formation in small diameter gravity sewers (SDGS) containing Proteobacteria, Bacteroidetes, Pseudomonas, and Enterobacter Chlorella vulgaris

Zhong et al. (2019)

metal pollution of Zn and Mn which effectively removes a maximum quantity of pollutants (Pani et al., 2017). Micropollutant degradation using moving-bed bioreactor (MBBR) removed metoprolol, erythromycin, citalopram, roxithromycin, and other pollutants (Torresi et al., 2017). The biofilm involved cleanup process takes a great stride with a series of findings and unsolving the mystery behind it. Table 21.2 provides an overview on the application of biofilm in degradation of a wide range of pollutants.

5. Marine biofilms Bacteria considered as early colonizers in marine ecosystem due to its adverse environmental changes. Marine biofilms are mainly known to cause biofouling on the artificial objects and on accumulated wastes. The chemotaxis occurs to the microorganisms near the surface and are passively transported via sea currents. Based on the nutrient variation (low and high), microbes are classified as oligotrophs (survives in low nutrient marine environment) and copiotrophs (survives on high nutrient environment). The marine microbes and phytoplanktons produces larger quantity of exopolymeric gels (colloids, mucous sheets, bundles). Bacteria utilizes these gel as a nutrient source by hydrolyzing using hydrolase enzyme. These exopolymeric gels - provides support, transports nutrients, solid particle aggregations, particle sedimentation, and contributes to carbon fluxes - in sea during initial colonization of bacteria. In marine snow aggregates, Roseobacter produces acylated homoserine lactone for communication. The marine bacteria also produces EPS similar to terrestrial bacteria but is composed of heteropolysaccharides including monosaccharides such as pentose, hexose and amino acids. The EPS containing

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sulfates, phosphates and uronic acids interacts and increases the concentration of metal ions that is required for Oligotrophic microbes (de Carvalho, 2018). Biofilms are also known for biocorrosion in marine environment with “carbon steel corrosion phenomena named as accelerated low waste corrosion (ALWC).” The phenomenon is not clearly understood but sulfur oxidizing and reducing bacteria are considered as key inducers. It is reported that the Fe solubilizing bacteria named Zetaproteobacteria initiates ALWC. This is due to the increase in inorganic nitrates in the marine environment. The Zetaproteobacteria also known to possess nitrogen fixing genes which are involved in the initiation of ALWC process (Dang and Lovell, 2016).

6. Marine biofilm in elimination of plastic debris Plastic pollution in marine environment affects the living ecosystem and the living organisms. Plastic tend to float due to its buoyancy but they also settle on the bottom of the sea/oceans and in the soil sediments. The degradation of plastics into micro and nanoplastics forms aggregates based on the surface charge. The formed plastic nanoparticles largely affect the photosynthetic microbes. The microalgae biosorption occurs with the polystyrene nanoparticles with carboxyl group while the amino groups inhibits the algal growth. The biofilm formation of the plastic debris varies with types of plastic and species of bacteria. This leads to decreased plastic hydrophobicity facilitating the transport beneath the air-water interface of marine environment. The dynamic study on nanoplastic effect on biofilm are yet to be explored (Okshevsky et al., 2020). The fate of microplastics in the marine environment reaches the tropic of food web and causes biomagnification in future (Fig. 21.3). The degradation of plastics is initiated by the weathering process leading to the loss of material integrity. Preceding the biofilm formation, the photodegradation (exposure to sunlight) is the commonly observed process of weathering. The photooxidation process involves series of steps: initiation, free radical formation, propagation, and termination. It further results in modified surface topography and chemistry of the plastics. This favors the adhesion of microbes onto the surface of plastic wastes leading to successive fragmentation. The surface distortion causes fragmentation of the plastics and forms high surface to volume ratio which aids in PLASTICS WEATHERING

BIOFILM FORMATION

FOOD WEB

NANOPLASTICS

MICROPLASTICS

FIGURE 21.3 Cycle of plastics in marine ecosystem.

7. Factors affecting the remediation using biofilm

enhancing biodegradation (Sabev et al., 2006) (Rummel et al., 2017). The fragmentation kinetics of plastics and its distribution after degradation by microbes is still unknown. The exposure to UV radiation is nil at benthos and the process of degradation is taken over by diverse microbial strains. But the fate of microplastics (MP) is still unknown (Andrady, 2015). The EPS production during biofilm formation makes the plastic waste sticky (Long et al., 2015). The growth of microbes forming biofilm is nurtured by the chemical additives used in the manufacture of plastics (Sabev et al., 2006). Biofilm as heavy metal pollution indicator determines the state of the environment. Pollutants degradation without bioaugmentation is aided by the native biofilm-forming microbes present in the environment. Polyaromatic hydrocarbon (PAH) degradation might require natural attenuation process in case of low concentration. The remediation of persistent organic pollutants (POPs) using cometabolism of biofilm enhances the degradation of hydrophobic pollutants like PAH (Mitra and Mukhopadhyay, 2016). The sorption mechanism in biofilm aids in the attachment of pollutants in the binding sites present in the cell wall, cytoplasm and EPS. The removal of sorbed pollutants occurs in two ways: either by degradation of pollutants by the biofilm or by the degradation of biofilm itself. QS in the engineered biofilm manufacturing enhances the degradation of POPs. Arthrobacter sp., Pseudochrobactrum saccharolyticum sp., and P. mendocina degrade the xenobiotics and chelates the heavy metals using EPS produced. Biofilm in nanoparticles removal using sorption is aided by the surfactant produced by the biofilm (Maurya and Raj, 2020).

7. Factors affecting the remediation using biofilm The enhancement pollutants remediation requires biofilm as they possess advantages compared to suspended isolates. The initial step for pollutant remediation is the formation of biofilm. The biofilm formation is affected by many factors as follows.

7.1 Nature of matrix The physicochemical nature of the matrix is a key factor in the attachment of the microbes. The rough or corrosive surface aids attachment of microbes effectively. The hydrophobic (nonpolar) matrix increases the attachment compared to hydrophilic and polar surfaces (Maurya and Raj, 2020).

7.2 pH The bacteria manage the pH fluctuations using proton motive force. The formation of transmembrane electrochemical gradient by eliminating the protons from cytoplasm stabilizes the pH of the bacteria. Rarely, bacteria protects itself from pH changes by EPS secretion (Maurya and Raj, 2020).

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7.3 Temperature The optimum temperature optimizes the metabolic activity thereby aids in the attachment to the matrices. The biofilm-forming regulator CsgD is temperature dependent which becomes unstable or inactive on temperature increase. The heat stress proteins on surface of the cells forms biofilm at higher temperature (Maurya and Raj, 2020).

8. Qs in pollutant degradation Bacteria with QS has the ability to degrade wide range of pollutants (phenol, hexadecane, phenanthrene and Pyrene). Addition of AHL to maintain the ability of phenolic degradation for longer duration and induced denitrification by QS mutant strains. The AI synthases encoded by abaI is involved in degradation of aromatic compounds and hexadecane (Anbazhagan et al., 2012). QS system and AIs regulates the gene expression and enzyme activity involved in degradation (Zhang and Li, 2016).

9. Biofilms as source for value added products The employment of microalgal EPS in pharmaceutical industries for the production of compounds such as antibacterial, antifungal, antiviral, antiinflammatory, and antitumor agents (Xiao and Zheng, 2016). The association of bakers’ yeast with Penicillium chrysogenum led to the production of biocapsule which increased the yield of fermentation foods due to its reusability (Moreno-Garcı´a et al., 2018). Lactic acid production by Leuconostoc sp., Enterococcus sp and Lactococcus sp. improved food texture and flavor (Chapot-Chartier and Kulakauskas, 2014). Leon - Romero et al. (2016) reported olive oil synthesis from Lactobacillus sp. and Candida boidinii.

10. Conclusion The exploitation of the resources available for welfare promotes standard of healthy living. The microbial world provides pros and cons in a range of applications. Converting the cons to pros increases the chances of wellness. Biofilm, considered a threat to living systems, is the better solution for creating a less toxic or polluted environment. Considering the ill effects of biofilm, continuous monitoring and proper handling prevents the pathogenicity. The solution for the pollution lies in itself. The better the cell-cell communication, the higher its efficiency. QS exploration unfolds truth about biofilm sustainability and mechanism of maintenance. The need to study the application of biofilm in the environmental cleanup never ends and leads to new discoveries.

References

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Kumar, A., Yuan, X., SarinaErgas, J.D., Van Langenhove, H., 2010. Model of a polyethylene microporous hollow-fiber membrane biofilm reactor inoculated with Pseudomonas putida strain To1 1A for gaseous toluene removal. Bioresour. Technol. 101 (7), 2180e2184. Lendenmann, U., Spain, J.C., &Smets, B.F., 1998. Simultaneous biodegradation of 2,4dinitrotoluene and 2,6-dinitrotoluene in an aerobic fluidized-bed biofilm reactor. Environ. Sci. Technol. 32, 82e87. ´ ., Domı´nguez-Manzano, J., Garrido-Ferna´ndez, A., Arroyo-Lo´pez, F.N., Leo´n-Romero, A Jime´nez-Dı´az, R., 2016. Formation of in vitro mixed-species biofilms by Lactobacillus pentosus and yeasts isolated from Spanish-style green table olive fermentations. Appl. Environ. Microbiol. 82 (2), 689e695. Li, Y.-H., Tian, X., 2012. Quorum sensing and bacterial social interactions in biofilms. Sensors 12 (3), 2519e2538. Li, C., Yue, Z., Feng, F., Xi, C., Zang, H., An, X., Liu, K., 2016. A novel strategy for acetonitrile wastewater treatment by using a recombinant bacterium with biofilm-forming and nitrile-degrading capability. Chemosphere 161, 224e232. Long, M., Moriceau, B., Gallinari, M., Lambert, C., Huvet, A., Raffray, J., Soudant, P., 2015. Interactions between microplastics and phytoplankton aggregates: impact on their respective fates. Mar. Chem. 175, 39e46. https://doi.org/10.1016/j.marchem.2015.04.003. Luthy, R.G., Dzombak, D.A., Peters, C.A., Roy, S.B., Ramaswami, A., Nakles, D.V., Nott, B.R., 1994. Remediating tar-contaminated soils at manufactured gas plant sites. Environ. Sci. Technol. 28 (6), 266Ae276A. Maurya, A., Raj, A., 2020. Recent advances in the application of biofilm in bioremediation of industrial wastewater and organic pollutants. In: Microorganisms for Sustainable Environment and Health. INC. https://doi.org/10.1016/b978-0-12-819001-2.00005-x. Mitra, A., Mukhopadhyay, S., 2016. Biofilm mediated decontamination of pollutants from the environment. AIMS Bioeng. 3 (1), 44e59. https://doi.org/10.3934/bioeng.2016.1.44. Møller, S., Sternberg, C., Bo Andersen, J., Christensen, B.B., Luis Ramos, J., Givskov, M., Molin, S., 1998. In situ gene expression in mixed-culture biofilms: evidence of metabolic interactions between community members. Appl. Environ. Microbiol. 64 (2), 721e732. Moreno-Garcı´a, J., Garcı´a-Martinez, T., Moreno, J., Carlos Mauricio, J., Ogawa, M., Luong, P., Bisson, L.F., 2018. Impact of yeast flocculation and biofilm formation on yeast-fungus coadhesion in a novel immobilization system. Am. J. Enol. Vitic. 69 (3), 278e288. Okshevsky, M., Gautier, E., Farner, J.M., Schreiber, L., Tufenkji, N., 2020. Biofilm formation by marine bacteria is impacted by concentration and surface functionalization of polystyrene nanoparticles in a species-specific manner. Environ. Microbiol. Rep. 12 (2), 203e213. https://doi.org/10.1111/1758-2229.12824. Pani, T., Das, A., Williams Osborne, J., 2017. Bioremoval of zinc and manganese by bacterial biofilm: a bioreactor-based approach. J. Photochem. Photobiol. B Biol. 175, 211e218. Pratt, L.A., Kolter, R., 1999. Genetic analyses of bacterial biofilm formation. Curr. Opin. Microbiol. 2 (6), 598e603. Rummel, C.D., Jahnke, A., Gorokhova, E., Ku¨hnel, D., Schmitt-Jansen, M., 2017. Impacts of biofilm formation on the fate and potential effects of microplastic in the aquatic environment. Environ. Sci. Technol. Lett. 4 (7), 258e267. https://doi.org/10.1021/ acs.estlett.7b00164. Sabev, H.A., Barratt, S.R., Greenhalgh, M., Handley, P.S., Robson, G.D., 2006. Biodegradation and biodeterioration of man-made polymeric materials. Fungi Biogeochem. Cycle. 212e235. https://doi.org/10.1017/CBO9780511550522.010.

References

Seo, Y., Lee, W.-H., George, S., Bishop, P.L., 2009. The application of a mulch biofilm barrier for surfactant enhanced polycyclic aromatic hydrocarbon bioremediation. Environ. Pollut. 157 (1), 95e101. Stewart, P.S., Franklin, M.J., 2008. Physiological heterogeneity in biofilms. Nat. Rev. Microbiol. 6 (3), 199e210. Ta-Chen, L., Chang, J.-S., Young, C.-C., 2008. Exopolysaccharides produced by Gordoniaalkanivorans enhance bacterial degradation activity for diesel. Biotechnol. Lett. 30 (7), 1201e1206. Torresi, E., Polesel, F., Bester, K., Christensson, M., Smets, B.F., Trapp, S., Andersen, H.R., GyPlo´sz, B., 2017. Diffusion and sorption of organic micropollutants in biofilms with varying thicknesses. Water Res. 123, 388e400. Tribedi, P., Sil, A.K., 2013. Low-density polyethylene degradation by Pseudomonas sp. AKS2 biofilm. Environ. Sci. Pollut. Control Ser. 20 (6), 4146e4153. Xiao, R., Zheng, Y., 2016. Overview of microalgal extracellular polymeric substances (EPS) and their applications. Biotechnol. Adv. 34 (7), 1225e1244. Yang, Z., Pei, H., Hou, Q., Jiang, L., Zhang, L., Nie, C., 2018. Algal biofilm-assisted microbial fuel cell to enhance domestic wastewater treatment: nutrient, organics removal and bioenergy production. Chem. Eng. J. 332, 277e285. Zhang, W., Li, C., 2016. Exploiting quorum sensing interfering strategies in gram-negative bacteria for the enhancement of environmental applications. Front. Microbiol. https:// doi.org/10.3389/fmicb.2015.01535. Zheng, T., Li, W., Ma, Y., Liu, J., Ren, J., 2020. Greywater: understanding biofilm bacteria succession, pollutant removal and low sulfide generation in small diameter gravity sewers. J. Clean. Prod. 122426. Zhong, N., Wu, Y., Wang, Z., Chang, H., Zhong, D., Xu, Y., Hu, X., Huang, L., 2019. Monitoring microalgal biofilm growth and phenol degradation with fiber-optic sensors. Anal. Chem. 91 (23), 15155e15162. Ziv-El, M.C., Rittmann, B.E., 2009. Systematic evaluation of nitrate and perchlorate bioreduction kinetics in groundwater using a hydrogen-based membrane biofilm reactor. Water Res. 43 (1), 173e181.

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Index Note: ‘Page numbers followed by “f ” indicate figures and “t” indicate tables.’

A Abortiporus biennis, 274e275 Abundant waste, 175 Acaligenes sp, 186 Accelerated low waste corrosion (ALWC), 453e454 Acetylcholinesterase (AChE), 168e169 Achromobacter sp, 186 Acid Black 210, 359 Acid dyes, 4, 130, 355e356, 421 Acid Orange 7 (AO7), 349e350 Acid Red, 8 Acid Red 1, 359 Acid Red 26, 133e134 Acid Violet 7, 3 Acid yellow 199, 8 Acid-precipitating polymeric lignin, 201e202 Acidic pharmaceuticals, 81 Acidithiobacillus ferroxidans, 182 Acinetobacter sp., 15, 182e183, 186, 426 A. calcoaceticus, 159e160, 203e204, 366 A. gerneri, 312e313 A. johnsonii, 54 Actinomycetes species, 228 Activated carbon, 424e425 adsorption by, 6e7 Activated Sludge Process (ASP), 74 Activated sludge system, 137 Active pharmaceutical ingredient (API), 77 Acyl-homoserine lactone (AHL), 449 Adenoviruses, 404e405 Adsorbent, 378e382 agricultural wastes, 378e379 bioadsorbents, 380e381 carbonaceous, 378 industrial wastes, 380 inorganic, 381e382 miscellaneous adsorbents, 382 polymeric, 379 Adsorption, 5e7, 44, 333e334. See also Biosorption by activated carbon, 6e7 by clay particles, 6 by silica gel, 7 by wood chips, 7 Advanced oxidation process (AOP), 13e14, 311e312

Aerobic cultures, dyes degradation by, 344e345 Aerobic degradation, 112 of azo dyes, 359e360 of dyes, 137e141 Aerobic respiration, 181 Aerobic sequencing batch reactors (ASBR), 74e75 Aerobic treatment, 134e135 Aeromonads sp., 167 Aeromonas sp, 15 A. caviae, 28 A. hydrophila var 24B, 145 Agaricus bisporus, 204 Agricultural wastes, 176e177, 409 adsorbents, 378e379 Agrochemicals, 287e288 Airemonium, 160 AIs 2, 449 Alcaligenes sp., 15, 201e202, 266 A. eutrophus, 380e381 BAPb. 1, 258 Alcanivorax, 164e165, 179 A. borkumensis, 167e168, 288 Aldicarb, 375 Aldrin, 41e42 Algae, 153, 186, 257e258, 405e406, 427 degradation mechanism with, 362 degradation of dyes, 141e142 Algal culture, degradation with, 16 Algal degradation of dyes, 345e346 Algal remediation of tannery wastewater constituents, 317 Aliphatic hydrocarbons, 287e288 Alkylphenols, 100 Alnus incana. See Mountain Alder (Alnus incana) Ameba, 405 Anaerobic contact reactor (ACR), 75e76 Anaerobic cultures, dyes degradation by, 344e345 Anaerobic degradation, 112 of azo dyes, 359e360 of dyes, 137e141 Anaerobic filter, 75e76 Anaerobic fixed film reactor (AFFR), 75e76 Anaerobic fluidized bed reactor (AFBR), 75e77 Anaerobic respiration, 181 Anaerobic treatment of pharmaceutical industrial wastewater, 75e76

461

462

Index

Analgesics, 176e177 Anthraquinone disulfonate (AQDS), 430 Anthraquinone sulfide (AQS), 430 Antibiotics, 70, 176e177 Anticonvulsant drugs (AC drugs), 71 Aphanothece flocculosa, 34 Archaea, 160e161, 289, 406 Aromatic compounds, 1e2, 15 Aromatic hydrocarbons, 287e288 Arsenic (As), 24e25, 243, 245e246, 405e406 Arsenicals, 305e307 Arthrobacter sp., 164e167, 186, 201e202, 455 A. globiformis, 313 A. nicotianae, 71e72 Aspergillus, 182e183, 409 A. niger, 33t, 258 A. tubingensis, 317e320 Association of Textile Chemists and Colorists (AATCC), 355e356 Astrazon Red GTLN, 419 Atrazine, 380 Auricularia polytricha, 29 Auto inducers (AIs), 449 Auxochromes, 2 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), 276e277 Azo dyes, 3, 127e128, 132e133, 355e356, 419e420, 433e434 classification, 356 classification, 421e423 acid dyes, 421 azoic dyes, 422 basic or cationic dyes, 421 direct dyes, 421 disperse dyes, 422 mordant dyes, 421e422 reactive dyes, 422 solvent dyes, 423 vat dyes, 422 decolorization and degradation of azo dyes by azoreductase, 428e429 different method for dyes removal, 423e427 biologycal method, 426e427 degradation methods of dyes, 424e426 different methods used in degradation of, 359 dyes, 420 enzyme-meditated decolorization and degradation of, 434e436 examples based on color, 358t factor affecting dyes degradation by biological method, 429e430 oxygen, 430

pH, 429 temperature, 429 mechanism of degradation and decolorization, 430 by azoreductases, 441e444 by laccase, 439e440 by peroxidases, 436e439 microbiological degradation of, 359e363 parameters involved during microbial azo-dye degradation, 364e367 properties, 423 strucutre of dyes, 423 textile effluents containing azo dyes impact on environment, 357 in textile industry, 356e359 Azoic dyes, 422 Azoreductase decolorization and degradation of azo dyes, 428e429 by laccase, 428e429 mechanism of degradation and decolorization by, 441e444 Azorhizobium, 403 Azospirillum lipoferum, 228

B Bacillus sp., 164e165, 259, 266, 428, 450 AK1, 167 B. amyloliquefaciens, 167 B. cereus, 231, 349e350, 367 B. denitrificans, 159e160 B. firmus, 145 B. flexus, 313 B. laterosporus, 28 B. licheniformis, 28, 364, 367 B. megaterium, 258 B. pumilus strain, 349e350 B. subtilis, 15, 136, 145, 159e160, 167, 228, 367, 426 1556WTNC, 72e73 B. tequilensis SN4, 206e207 Bacteria, 153, 159e160, 186, 258e259, 265e266, 403 biosorption by, 28e29 degradation, 15e16 immobilization of cells for dyes degradation, 15e16 mechanism, 360e361 of textile dyes, 336e344 and fungi, 114e116 lignin degradation by, 201e203 Bacterial bioremediation, 292e293

Index

Bacterial cultures, 312e313 Bacterial degradation, 72e73, 426 of dyes, 136 Bacterial ligninolytic enzymes, 206e207 Bacterial remediation of tannery effluent constituents, 313 Bacteriophages, 404e405 Bacterivorous grazers, 405 Basic dyes, 4, 130, 421 Basidiomycota, 204 Beam-house process, 303 Benzene, toluene, ethylbenzene, xylene (BTEX), 221e222 Benzene hexachloride (BHC), 41e42 Bioaccumulation, 47e48, 50, 244, 252e253, 254te255t, 266e267, 379 Bioadsorbents, 380e381 Bioaugmentation, 30e31, 51, 163e164, 182e183 microbial, 30e31 Biobleaching in paper industry, 230e231 Biochemical mechanism of pesticides bioremediation, 52e54 inference, 54 Biochemical oxygen demand (BOD5), 305 Biocides, 48e50 Bioconversion of lignin to value-added bioproducts, 209e214 Biodegradation, 71e72. See also Anaerobic degradation; Degradation approaches for pharmaceutical wastes treatment, 72e77 bacterial degradation, 72e73 enzymatic degradation, 74e77 fungal degradation, 73 of colors, 231e232 of pesticides, 382e389 Bioelectrochemical systems, 308e310 Bioenergy, 195 Bioenhancement, 163e164 Biofilm associated proteins (bap), 156 Biofilms, 154e161, 293e294, 449 application in bioremediation, 165e169 inorganic pollutants, 166e167 oil-contaminated water, 167e168 pesticides, 168e169 POPs, 165e166 PPCPs, 168 bioreactors, 164 in biofilm formation, 451, 452t bioremediation, 161e162 in bioremediation, 450

challenges in biofilm mediated bioremediation, 169 composition, 155e156 factors affecting remediation using, 455e456 nature of matrix, 455 pH, 455 temperature, 456 formation, 153 factors affecting, 157e159 mechanism, 156e157 formed by different microbial species, 159e161 marine biofilms, 453e454 in elimination of plastic debris, 454e455 mediated remediation, 154, 452e453 Qs in pollutant degradation, 456 role in bioremediation, 162e163 strategies for use of, 163e164 as source for value added products, 456 technology for wastewater recycling, 349e350 types of pollutants remediated by, 164e165 Biofiltration, 184e185 Biogas, 139 Biogenic nanoparticles, 118 Bioleaching, 36, 182, 292 Biological agents, 175e176 Biological degradation of lignin, 198e203 lignin degradation by bacteria, 201e203 fungi, 199e201 Biological enzymes for environmental bioremediation, 273e277 laccases, 276e277 MMO, 276 monooxygenases, 275 oxidoreductases, 274 oxygenases, 275 peroxidases, 274e275 Biological methods, 14e18, 426e427. See also Chemical methods algae, 427 bacterial degradation, 426 biological treatment, 134e144 aerobic and anaerobic degradation of dyes, 137e141 algae degradation of dyes, 141e142 bacterial degradation of dyes, 136 biosorption studies for dyes degradation, 143e144 enzymatic degradation of dyes, 142e143 fungal degradation of dyes, 135e136 decolorization of yeast, 427

463

464

Index

Biological methods (Continued) techniques of textile dyes, 128f treatment of dispersed textile dyes, 144e145 decortication by fungi, 427 degradation with algal culture, 16 bacteria, 15e16 fungi, 16 immobilization of cells for dyes degradation, 15e16 white-rot fungi, 16e17 yeast, 16 enzymatic decolorization and degradation of azo dyes, 427 enzyme system of white-rot fungi, 17e18 methods for textile dyes treatment, 134 microorganisms, 419 textile dyes and impact on environment, 131e134 for textile dyes degradation, 334e350, 337te343t algal degradation of dyes, 345e346 biofilm technology for recycling of wastewater, 349e350 biosorption assay for textile dye degradation, 347 dyes degradation by use of anaerobic and aerobic cultures, 344e345 enzymes role in degradation of textile dyes from wastewater, 346e347 fungi as biodegradable agent for textile dyes, 335e336 MFC technology for dyes biodegradation, 347e349 use of bacteria for degradation of textile dyes, 336e344 types of dyes, 129e131 Biological oxygen demand (BOD), 74e75, 303e305, 405e406 Biological treatment of tannery wastewater, 312 for textile dispersed dyes, 145 Biomagnification, 47e48 Biomass, 195 Biomedical waste, 409e410 Biomimetic fat cell (BFC), 379 Biomineralization, 291e292 Biopiles, 184 Biopiling, 52 Biopulping in paper industry, 230e231 Bioreactors, 52 in biofilm formation, 451, 452t Bioremediation, 24, 28e36, 117, 153, 161e162, 175e176, 243, 250e252, 266

advantages of bioremediation over conventional methods, 179e181 bioaugmentation, 30e31 biofilm role in, 162e163, 450 application in, 165e169 strategies for use of, 163e164 bioleaching, 36 biosorption, 28e30 biostimulation, 35e36 bioventing and biosparging, 33e34 challenges in biofilm mediated bioremediation, 169 microbial waste management by, 189e190 cyanoremediation, 34e35 different microorganisms capable of bioremediation of specific compounds, 180t factors, 52 membrane protein complex in electrogenic bacteria for, 270e273 Geobacter sulfurreducens cytochromes and nanowires in heavy metals reduction, 272e273 redox mediators of Pseudomonas aeruginosa in environmental bioremediation, 272 respiratory complexes of Shewanella oneidensis and heavy metals biodegradation, 270e272 microbial-electrochemical systems for, 268e270 mycoremediation, 32e33 phytoremediation, 31e32 strategies bioremediation of heavy metals and radionuclides, 295e297 limitations and future prospects, 297e298 microbial interactions with radionuclides and heavy metals, 289e292 organisms involved in bioremediation, 292e295 of tannery wastewater, 312 technologies types, 50e52 Bioremediators for heavy metals, 256e259 algae, 257e258 bacteria, 258e259 fungi, 258 Biosorption, 8, 28e30, 266e267, 291 assay for textile dye degradation, 347 by bacteria, 28e29 by fungi, 29e30 studies for dyes degradation, 143e144 Biosparging, 33e34, 51 Biostimulation, 35e36, 183 Biosurfactants, 155e156

Index

Biotransformation, 266e267 Bioventing, 33e34, 51, 183e184 Biovolatilization, 292 Bitter gourd peroxidase (BGP), 436 Bjerkandera sp., 203e204 B. adusta, 16, 235 MUT 2295, 73 Bloodroot (Sanguinaria canadensis), 355 Blue multicopper oxidases, 224e225 Borassus aethiopum, 312 Botryosphaeria sp., 199e200 Brachymonas denitrificans, 159e160 Bradyrhizobium, 178e179, 403 Brevibacillus panacihumi strain, 349e350 Brevundimonas, 30e31 Brominated flame retardants (BFRs), 100, 107e108 3-bromo-2,2-bis(bromomethyl) propanol (TBNPA), 107 Brown algae, 294e295 Brown macroalgae, 294e295 Brown-rot fungi, 200e201 Burkholderia, 182e183 Butternut (Juglans cinerea), 355 Butyl benzyl phthalate (BBP), 106

C C/N ratio, 196 Cadmium (Cd), 1e2, 23e25, 243e244, 246, 287e288, 405e406 Cadmium sulfide (CDS), 80 Canaigre dock (Rumex hymenosepalus), 355 Candida C. albicans, 160 C. boidinii, 456 C. parapsilosis, 33t C. tropicalis, 145 Carbamate pesticide, 375 Carbofuran, 375 Carbon nanotubes (CNTs), 81e82, 382 Carbon nitride, 83 Carbon-oxygen bonds, 197e198 Carbonaceous adsorbents, 378 Carbonecarbon bonds, 197e198 Carcinogen benzidine, 127e128 Catalase-peroxidase (Amyco1), 207 Catalysis, 79 Catechol 2, 223 Cationic dyes, 421 Caulerpa lentillifera, 141e142 Cavitations treatment, 311e312 CBZ, 81

Cellulose, 195 Cellulosimicrobium sp., 166e167 Cerrena maxima, 205e206 Cesium (Cs), 288 Charged filtration. See Nanofiltration Chelators, 253 Chemical agents, 1e2 Chemical contaminants, 287e288 Chemical expulsion, 311e312 Chemical fertilizers, 265 Chemical methods, 9e12, 424e426. See also Biological methods cucurbitiril, 11 fenton method, 10 ozonation, 10e11 sodium hypochlorite, 11e12 Chemical oxidation method, 425 Chemical oxygen demand (COD), 1e2, 72e73, 134e135, 176e177, 305, 405e406 Chlamydomonas sp, 186 C. reinhardtii, 362 Chlorella C. ellipsoidea, 362 C. pyrenoidosa, 141e142 C. sorkiniana, 28 C. vulgaris, 362 Chlorinated chemical compounds, 48e50 Chlorinated compounds, 287e288 Chlorinated ethenes, 166 Chlorinated organic pesticides, 41 Chloroflexi, 166 Chromium (Cr), 26e27, 176e177, 243e244, 287e288, 305e307 Chromophores, 2, 421 Chromophoric dissolved organic matter (CDOM), 106e107 Chrysonilia sitophila, 199e200 CI. See Color index (CI) Citrobacter C. freundii, 231 C. youngae, 71e72 Citrobacteria, 266 Citromonas sp, 186 Clay particles, adsorption by, 6 Clofibric acid, 81 Closterium sp, 426 Clostridium sp., 15 C. perfringens, 136 Coagulating agent, 311e312 Coagulation, 7e8, 433e434 coagulation/flocculation, 310e311

465

466

Index

Coal conversion to low molecular mass fraction, 230 Color index (CI), 129, 355e356 CI Acid Black 1, 140e141 CI Acid Blue25, 137e138 CI Acid Orange 7, 138e139 CI Acid Orange 10, 140e141 CI Acid Red 348, 137e138 CI Acid Yellow 61, 137e138 CI Direct Red 2, 140e141 CI Direct Red 28, 140e141 CI Reactive Black 5, 137 CI Reactive Red 141, 140e141 CI Solvent Yellow 1, 133e134 CI Solvent Yellow 2, 133e134 Colors biodegradation, 231e232 Comamonas C. denitrificans, 159e160 C. testosteroni, 313 Combined aerobiceanaerobic treatment, 139 Cometabolic system, 71e72 Cometabolism, 181, 386e387 Complexation, 292 Composting, 52, 186, 402 Coniferyl alcohol, 196e197 Conventional activated sludge (CAS), 74 Conventional wastewater treatment, 153 Copper (Cu), 26, 224e225, 245, 295 Coprinopsis atramentaria, 258 Coriolopsis sp., 335 C. gallica, 233 C. polyzona, 233 Coriolus versicolor, 16e17, 367 Corneybaterium sp., 15 Corneyrium sp, 426 Cosmarium sp, 141e142 Coupled spectroscopic and electrochemical techniques, 279e281 Cronobacter sakazakii, 159e160 Crude oil, 48e50 Cucurbita maxima, 11 Cucurbitiril, 11 Cunninghamella polymorpha, 145 Cyanobacteria, 402e403 Cyanobacterial EPS, 162e163 Cyanoremediation, 34e35 Cyclic voltammetry (VC), 277e278 Cycloclasticus spp., 164e165 Cyprus alternifolius, 312 Cys. See Cysteine (Cys) Cysteine (Cys), 225 Cytochrome P450, 275

Czapek yeast extract (CYE), 32

D Daphnia magna, 81e82 Dead microbial cells, 380e381 Dechloromonas aromatic, 288 Decolorization of azo dyes by azoreductase, 428e429 by azoreductases, 441e444 by laccase, 439e440 by peroxidases, 434e435 process, 139 treatment of dispersed textile dyes, 144e145 biological treatment for textile dispersed dyes, 145 of yeast, 427 Decortication by fungi, 427 Degradation of azo dyes by azoreductase, 428e429 by azoreductases, 441e444 by laccase, 439e440 mechanism with algae, 362 with bacteria, 360e361 with fungi, 362e363 methods of dyes, 424e426 physical and chemical method, 424e426 pathways of phthalate esters, 111e112 by peroxidases, 434e435 Dehalococcoides, 166 Dehalogenation, 388 Deinococcus radiodurans, 288 Delignification of lignocelluloses, 229 Demethylation, 388 Depolymerization of lignin, 196 Derris eliptica, 371 Desmodesmus sp., 141e142 Desulfobacterium, 182e183 Desulfomonile tiedjei, 380e381 Detachment of biofilm, 157 Detoxification of heavy metals, 253e256, 254te255t of textile dyes, 128, 134 of textile wastewaters, 141 Di(2-ethylhexyl)phthalate (DEHP), 106 Dibenzothiophene (DBT), 230 Dibutyl phthalate (DBP), 106 Dichloro-diphenyl-trichloroethane (DDT), 41, 371, 374

Index

3,4-dichloroaniline (3,4-DCA), 408 Diclofenac (DCF), 70, 80 Dicofol, 374 Dieldrin, 41e42, 374 Diethyl phthalate (DEP), 106 Dimethyl phthalate (DMP), 106 Dimethylformamide (DMF), 305e307 Dioxins, 166 3-dioxygenase protein, 223 Dipole-dipole interaction, 449e450 Direct dyes, 4, 130, 421 Direct extracellular electron transfer (DEET), 267e268 Directred80, 8 Disperse Blue 6, 130 Disperse dyes, 130, 355e356, 422 Dispersed textile dyes, decolorization treatment of, 144e145 Dispersion of biofilm, 157 DNA viruses, 404e405 Dry cell weight (DCW), 209e212 Dry fabric production, 329 Dye wastewater. See Dyedeffluent Dye-decolorizing peroxidases (DyPs), 203, 206 Dye(s), 1e2, 127e128, 287e288, 420 degradation by use of anaerobic and aerobic cultures, 344e345 effluent, 329e330, 433e434 removal methods, 333e350 types and characteristics of, 332 types and toxicity, 2e4, 5t, 129e131 acid dye, 4 azo dyes, 3 basic dye, 4 direct dye, 4 organic dyes, 129f vat dye, 4 Dyeing, 1e2

E Effective microorganism (EM), 408 Eichhornia crassipes, 312 Electro coagulation, 7 Electro Fenton (EF), 91 Electro-chemical precipitation, 311e312 Electro-dialysis, 310e311 Electro-Fenton process, 10 Electro-oxidation process, 311e312 Electro-spinning, 83 Electrocatalytic oxidation (EC oxidation), 88 Electrochemical characterization of redox enzymes, 277e281

coupled spectroscopic and electrochemical techniques, 279e281 cyclic voltammetry, 277e278 EIS, 278e279 Electrochemical coagulation (ECC), 91 Electrochemical impedance spectroscopy (EIS), 278e279 Electrochemical oxidation (EC), 91 Electrochemically active biofilms (EAB), 164e165 Electrocoagulation, 311e312 Electrocoagulation combined with photoelectro Fenton (EC/PEF), 91 Electron paramagnetic reverberation/resonance (EPR), 224e225, 280e281 Electron transfer (ET), 267 Electrostatic interaction, 156 Elphidim, 405 Emerging micropollutants (EMPs), 70, 99. See also Persistent organic pollutants (POPs) advancements in microbial cell-based wastewater treatment, 117e119 fate of EMPs in aqueous environment, 109e111 microbial cells and enzymes in wastewater treatment, 112e117 microbial degradation of micropollutants, 111e112 perspectives of microbial degradation and challenges, 117 Emerging pollutants as micropollutants, 100e109 BFR, 107e108 perfluorinated compounds, 108e109 pesticides, 102e106 pharmaceuticals, 101e102 plasticizers, 106e107 Endosulfan, 41, 374 Energy Dispersive X-ray Fluorescence (EDXRF), 246e247 Energy production, 178 Enrofloxacin, 73 Entamoeba, 405 Enterobacter sp., 450 E. aerogenes, 295 E. agglomerans, 159e160 E. hormaechei, 71e72 Enterococcus sp., 15, 136, 426, 456 E. faecalis, 167 Environment heavy metals toxicity in, 247e248 microorganisms in, 403e406 textile dyes and impact on, 131e134 textile effluents containing azo dyes impact on, 357 Environmental balance, 127

467

468

Index

Environmental bioremediation biological enzymes for, 273e277 Pseudomonas aeruginosa redox mediators in, 272 Environmental pollutants, 176e177, 289 Environmental pollution, 23, 175 Environmental protection, indigenous microorganisms role for, 190e191 Environmental Protection Agency (EPA), 245e246, 305e307 Environmental safety, microorganisms in, 410e413 Enzymatic decolorization and degradation of azo dyes, 427 Enzymatic degradation, 74e77, 385e386 of dyes, 142e143 Enzyme(s) associated with lignin degradation, 203e207 bacterial ligninolytic enzymes, 206e207 laccase, 205e206 lignin peroxidase, 203e204 MnP, 204 versatile peroxidase, 205 enzyme-meditated decolorization and degradation of azo dye, 434e436 role in textile dyes degradation, 346e347 system of white-rot fungi, 17e18 Ericameria nauseosa. See Rubber rabbitbrush (Ericameria nauseosa) Escherichia, 266 E. coli, 15, 136, 167, 296e297, 426, 428 Ethanol, induction of, 208 Euchema spinosum, 362 Euglena sp, 186, 405 European Union (EU), 305e307 Evaporation treatment, 310e311 Ex situ approach, 50 Ex situ bioremediation, 162, 164 Exiguobacterium homiense, 313 Exopolysaccharides (EPSs), 155, 163, 449 Explosives, 48e50 Extracellular DNA, 159 Extracellular electron transfer (EET), 267 Extracellular ligninolytic enzyme systems, 199e200 Extracellular nucleic acid (eDNA), 156 Extracellular polymeric substances (EPS), 116e117, 291, 349e350 Extracellular sequestration, 253 Extradiol ortho pathway, 112

F Fenton method, 10 Fenvalerate, 376 Fermentation, 181 Filamentous fungi, 294 Filtration method, 425 Flame atomic absorption spectrometer (FAAS), 246e247 Flame retardants, 48e50 Flavin adenine dinucleotide (FAD), 270 Flavin mononucleotide (FMN), 270 Flavobacterium sp, 186, 259 Flocculation, 7e8, 433e434 Food, 371 Formate dehydrogenase (FDH), 17 Fossil fuel consumption, 195 Fourier transform infrared spectroscopy (FT-IR), 80 Free living organisms, 405 Free planktonic cells, 162e163 Fungal cultures, 312e313 Fungal degradation, 73 of dyes, 135e136 Fungal remediation of tannery wastewater constituents, 317e320 Fungi, 153, 160, 189, 258, 289, 404 bacteria and, 114e116 as biodegradable agent for textile dyes, 335e336 biosorption by, 29e30 decortication by, 427 degradation mechanism with, 16, 362e363 lignin degradation by, 199e201 Fusarium, 160, 182 F. chlamydosporium, 312e313, 317e320

G G-Lignin, 196e197 Galacto mycesgeotrichum, 16 Genetic engineering, 117e118 Genetically modified organisms, 308e310 Geobacillus, 15, 426 Geobacter sulfurreducens, 267e268, 272e273 Giardia, 405 Gloeophyllum G. sepiarium, 33t G. striatum, 73 G. trabeum, 200e201 Glycoluril, 11 Gold, 23e24 Gordonia sp., 450 Gram-negative bacterial strains, 136

Index

Gram-positive bacterial strains, 136 Granular carbon electrode (GCE), 347e348 Green techniques bioremediation, 28e36 different heavy metals and impacts, 24e27, 27t arsenic, 24e25 cadmium, 25 chromium, 26e27 copper, 26 lead, 25 mercury, 26 nickel, 26 factors affecting bioremediation, 37 nutrients availability, 37 pH, 37 temperature, 37 pathway by heavy metals, 24f Greenhouse gases, 287e288 Groundwater (GW), 86 contamination, 176 Growth substrate. See Primary substrate GSH-Lignin, 196e197

H Haematococcus sp., 362 Haloarcula vallismortis, 289 Halobacterium, 289 Halococcus, 289 Haloferax, 289 H. mediterranei st., 289 H. volcanii, 289 Halomonas sp., 450 H. aquamarina TA-04, 166e167 Heavy metals, 1e2, 23, 166e167, 176e177, 243, 287e288, 450 analysis, 246e247 bioaccumulation, 252e253 biodegradation, 270e272 bioremediation, 250e252, 295e297 contamination, 265e266 detoxification, 244, 253e256 different types of bioremediators for heavy metals, 256e259 in industrial effluent, 245e246 industrial effluent containing heavy metals, 244e245 metal finishing, 244 mining, 245 nuclear plants, 245 textiles industries, 245 integrated system, 259e260 microbial interactions with, 289e292

toxicity, 23, 247e250 environment, 247e248 humans, 249e250 microorganisms, 248e249 plants, 248 Heme-peroxidases, 225e226 Hemicellulose, 195 Hemorrhagic fever virus, 404e405 Hepatitis B virus, 404e405 Hepatitis virus A, 404e405 Hepatitis virus C, 404e405 Hepatitis virus D, 404e405 Heptachlor, 41, 374 Herbicides, 391 Herpes virus, 404e405 Heterobasidion annosum, 199e200 Hexabromocyclododecanes (HBCDs), 107 Hexavalent chromium, 305e307 High-pressure liquid chromatography (HPLC), 246e247 Higher internal resistance (HIR), 347e348 Histidines (His), 225 Horseradish peroxidase (HRP), 436, 438e439 Household waste, 177 HPI. See N-hydroxyphthalimide (HPI) Humans, heavy metals toxicity in, 249e250 Hydrolases EC3, 74 Hydrolysis, 388 Hydrolytic enzymes, 116 Hydrophobic pharmaceuticals, 77 Hydrothermal method, 80 4-hydroxybenzoic acid (HBA), 209e212 1-hydroxybenzotriazole (HBT), 205e206 Hydroxycinnamic corrosive, 223 Hydroxyl radical scavengers, 84 Hydroxylase, 136

I Ibuprofen, 81 ICP-MS, 246e247 Idyllic pesticide, 371e372 Immense diversity of microorganisms, 401e402 Immobilization of cells for dyes degradation, 15e16 Immobilized lipase, 223 Immobilized microbial technology application, 389 In situ approach, 50 In situ bioremediation, 162 Indigenous microorganism role for environmental protection, 190e191 Indirect dyes. See Mordantddyes

469

470

Index

Indirect extracellular electron transfer (IEET), 267e268 Induction nutrients, 208 Industrial effluent arsenic, 245e246 cadmium, 246 heavy metals in, 245e246 lead, 246 mercury, 246 Industrial wastes, 406e408 adsorbents, 380 Industrial wastewater, 1e2 Industrialization, 175, 329 Influenza virus, 404e405 Inorganic adsorbents, 381e382 Inorganic pollutants, 166e167, 176e177 Insecticides, 41e42, 265 Integrated system of wastewater treatment, 118e119 Intradiol ortho pathway, 112 Ion-exchange method, 12, 310e311, 333e334 Irpex lacteus, 199e200, 231e232 Irradiation, 8, 333e334

J Juglans cinerea. See Butternut (Juglans cinerea)

K Keratin, 409 Kerstersia sp. VKY1, 167 Klebsiella sp., 15, 266, 426 K. pneumonia, 136, 312e313 K. variicola, 312e313 Kosakonia cowanii, 312e313 Kraft pulping process, 198

L Laccases, 18, 115, 205e206, 224e225, 276e277, 428e429, 439 laccase-arbiter system, 234 laccase-dependent enzymatic technique, 235 structure and catalytic mechanism, 224e225 mechanism of degradation and decolorization by, 439e440 Lactobacillus sp., 15, 426, 456 Lactococcus sp., 456 Land farming, 51e52, 186 LangmuireHinshelwood mechanism (LH mechanism), 84e85 Lead (Pb), 1e2, 23e25, 176e177, 246, 405e406 Leathers, 303

Lenzites betulinus, 204 Leuconostoc sp., 456 Life expectancy, 69 Lignin, 195e196 bioconversion of lignin to value-added bioproducts, 209e214 biological degradation of, 198e203 chemical structure and sources, 196e198 current challenges and future perspectives, 214e215 enzymes associated with lignin degradation, 203e207 lignin-degrading peroxidases, 206 ligninolytic enzymes regulation, 207e209 Lignin peroxidase (LiP), 17, 199e200, 203e204, 222, 226e227, 235, 436, 438 Ligninases, 436 Ligninolytic enzymes, 223 application, 228e236 biodegradation of colors, 231e232 biopulping and biobleaching in paper industry, 230e231 coal conversion to low molecular mass fraction, 230 delignification of lignocelluloses, 229 ligninolytic enzymes role in lignin degradation, 235e236 lignolytic enzymes applications in various industries, 234e235 polymerization in polymer ventures, 231 removal of recalcitrant polyaromatic hydrocarbons, 229e230 soil treatment, 233e234 wastewater treatment, 232e233 heme-peroxidases, 225e226 improvement strategies for ligninolytic enzyme production, 236e237 laccases, 224e225 LiP, 226e227 MnP, 227 molecular structure and mechanisms of, 223 regulation, 207e209 induction nutrients, 208 induction of ethanol, 208 induction of metal ions, 207e208 induction of phenolic compounds, 208e209 role in lignin degradation, 235e236 sources of, 227e228 Ligninolytic system of white root fungi, 221e222 Lignins, 176e177 Lignocelluloses, 195 delignification of, 229

Index

Lignosulfonate, 198 Lindane, 41e42 Linear voltammetry (VL), 277 Lipid regulator drugs (LR drugs), 71 Lipoamide dehydrogenase (LpdG), 272 Listeria monocytogenes, 159e160 Livestock waste, 177 Low-density lipids, 71 Luffa cylindrica, 28 Lyases EC4, 74 Lysinibacillus AK2, 167 L. fusiformis, 349e350

M Macromolecules, 155e156 Malachite green, 127e128 Manganese peroxidase (MnPs), 17e18, 199e200, 204, 227, 235, 436e437 Marine biofilms, 453e454 in elimination of plastic debris, 454e455 Marinobacter hydrocarbonoclasticus SP17, 167e168 Marinomonas mediterranea, 228 Massillia, 159e160 Maturation of biofilm, 157 Mauveine, 127 Maxilon Blue GRL, 419 MDR M. tuberculosis (MDRTB), 71 Medicine, 69 Melanocarpus albomyces, 224 Membrane bioreactor (MBR), 77 Membrane filtration, 310e311, 425 Membrane proteins mediated microbial-electrochemical remediation technology biological enzymes for environmental bioremediation, 273e277 electrochemical characterization of redox enzymes, 277e281 membrane protein complex in electrogenic bacteria for bioremediation, 270e273 microbial electrochemistry, 267e270 perspectives, 281e282 Membrane technology, 8e9 microfiltration, 8 nanofiltration, 9 reverse osmosis, 9 ultrafiltration, 9 Mercury (Hg), 1e2, 23e24, 26, 176e177, 246, 405e406 Mesorhizobium, 178e179, 403 Metabolic residues of phthalate esters, 111e112

Metagenomic approach for bioprospecting potential microbes and enzymes, 321e322 Metal finishing, 244 Metal ions, induction of, 207e208 Metal resistance mechanisms, 32 Metallothioneins (MT), 253 Methane monooxygenase (MMO), 276, 281 Methoxychlor, 374 Methylaminos triphosphorous, 281 Methylation, 388 Methylibium petroleiphilum, 288 Microalgae, 116e117 Microbes, 175e178, 248e249, 401e402 assisted phytoremediation, 185e186 microbe-based biofertilizers, 402 microbe-mediated detoxification processes, 179e181 wastewater treatment using, 186e189 Microbial azo-dye degradation, 364e367 effect of carbon source, 364 dye concentration, 366 inoculum size, 366 nitrogen source, 364e366 pH, 366 Microbial bioaugmentation, 30e31 Microbial biofilms, 155 Microbial biosensors, 402 for detection and monitoring of contaminant, 322e323 Microbial cells bacteria and fungi, 114e116 hydrolytic enzymes, 116 laccases, 115 oxidoreductases, 115 peroxidases, 115e116 and enzymes in wastewater treatment, 112e117 microalgae, 116e117 microbial cell-based wastewater treatment advancements in, 117e119 biogenic nanoparticles, 118 genetic engineering, 117e118 integrated systems, 118e119 Microbial communities, 153 Microbial degradation, 52e53 biochemical mechanism of pesticides bioremediation, 52e54 biomagnification, 47e48 cometabolism, 386e387 enzymatic degradation, 385e386 microbial potential, 48e50 of micropollutants, 111e112

471

472

Index

Microbial degradation (Continued) degradation pathways and metabolic residues of phthalate esters, 111e112 mineralization, 386 other microbial degradation pathways, 387e388 dehalogenation, 388 demethylation, 388 hydrolysis, 388 methylation, 388 nitro reduction, 388 oxidation, 388 of pesticide technology, 384e389 construction and application of multistrain complex system, 389 immobilized microbial technology application, 389 transgenic technology application, 388e389 pesticides effect on environment health, 41e47 pesticides, 43 of rhizosphere, 391 types of bioremediation technologies, 50e52 Microbial detoxification, 179e181 Microbial electrochemistry, 267e270 microbial-electrochemical systems for bioremediation, 268e270 Microbial electrolysis cells, 402 Microbial fuel cell (MFC), 90 for dyes biodegradation, 347e349 technology, 347 Microbial interactions with radionuclides and heavy metals, 289e292 Microbial lipids, 209e212 Microbial population, 401e402 Microbial potential, 48e50 Microbial remediation, 312e320. See also Environmental bioremediation bacterial remediation of tannery effluent constituents, 313 fungal remediation or mycoremediation of tannery wastewater constituents, 317e320 phycoremediation or algal remediation of tannery wastewater constituents, 317 Microbial species, biofilm formed by different, 159e161 Microbial waste management, 181e186 bioaugmentation, 182e183 biofiltration, 184e185 bioleaching, 182 biopiles, 184 biostimulation, 183 bioventing, 183e184

challenges in microbial waste management by bioremediation, 189e190 microbe assisted phytoremediation, 185e186 Microbial-electrochemical technologies (MET), 266e267 systems for bioremediation, 268e270 Microbiological degradation of azo dyes, 359e363 advantages of using microbiological consortia, 363 effect of agitation, 367 degradation mechanism with algae, 362 bacteria, 360e361 fungi, 362e363 effect of temperature, 366e367 effect of time, 367 Micrococcus dermacoccus sp, 15 Micrococcus sp, 259, 426 Microcolony formation, 156e157 Microfiltration, 8 Micromonospora chalcea, 384 Microorganisms, 71, 117, 128e129, 287e288, 402 advantages of bioremediation over conventional methods, 179e181 challenges in microbial waste management by bioremediation, 189e190 different approaches for microbial waste management, 181e186 in environment, 403e406 algae, 405e406 archaea, 406 bacteria, 403 fungi, 404 protozoa, 405 viruses, 404e405 in environmental safety, 410e413 heavy metals toxicity in, 248e249 immense diversity of, 401e402 indigenous microorganisms role for environmental protection, 190e191 pesticide degradation of, 388 role in waste management, 177e179, 406e410 agricultural wastes, 409 biomedical waste, 409e410 energy production, 178 industrial waste, 406e408 municipal waste, 408 oil spills treatment, 179 radioactive waste, 410 sewage treatment, 178 soil treatment, 178e179

Index

wastes types and sources, 176e177 wastewater treatment using microbes, 186e189 Microplastics (MP), 454e455 Micropollutants emerging pollutants as, 100e109 microbial degradation of, 111e112 Mineralization, 90, 386 Mining, 245 Mn peroxidase (MnP), 222 Monocystic, 405 Monomethoxy phenoxide, 196e197 Monooxygenases, 275 Monosaccharides, 225 Mordant, 332 dyes, 130, 421e422 Morganella sp., 15 Mountain Alder (Alnus incana), 355 Moving-bed bioreactor (MBBR), 452e453 Muconic acid, 214 Multi-walled carbon nanotubes (MWCNTs), 80e81, 347e348, 382 Multicopper oxidases (MCOs), 224e225 Multiple drug resistant (MDR), 71 Municipal waste, 408 Myceliophora thermophila, 276 Mycoremediation, 32e33, 294 of tannery wastewater constituents, 317e320 Myrothecium verrucaria, 367

N N-hydroxyacetanilide (NHA), 205e206 N-hydroxyphthalimide (HPI), 205e206 NAD-dependent formate dehydrogenase, 17 Nanofiltration (NF), 9, 359 Nanowires in heavy metals reduction, 272e273 National institute of environmental health sciences (NIEHS), 70 Natural biofilm formation process, 163 Natural dyes, 355 Nematoloma frowardie, 230 Neocosmopura, 160 Nernst equation, 279e280 Next-generation sequencing (NGS), 321e322 Nickel (Ni), 26, 176e177, 243e244 Nicotinamide adenine dinucleotide (NAD), 274 Nitrifying Activated Sludge process (NAS process), 75 Nitro reduction, 388 Nitrobacter hamburgensis, 288 Nitrogen cycle, 178e179 Nitrosomonas europaea, 288 Nocardia, 201e202

N. amarae, 384 N. farcinia, 384 N. vaccini, 384 Noctiluca, 405 Nonessential metals toxicity, 23e24 Nonfiltration, 425 Nonmetal doped TiO2, 79 Nonsteroidal antiinflammatory drugs (NSAIDs), 70 Nonsulfur lignins, 198 Nostoc muscorum, 35, 141e142 Nuclear plants, 245 Nuclear waste, 287e288 Nutrients availability, 37 induction, 208 Nux Vomica, 371

O O,O-diethyl-O-(2-quinoxalinyl)-phosphorothioate (QP), 168e169 b-O-4 ether bond, 197e198 O-4-bromo-2-chlorophenyl O-ethyl S-propyl phosphorothioate (PF), 168e169 b-O-4-linked ethers, 196 o-tolidine, 3 Ochrobactrum anthropi, 54 Oil spills treatment, 179 Oil-contaminated water, 167e168 Optically transparent thin-layer electrode (OTTLE), 280e281 Organic compounds, 48e50 Organic pollutants, 176e177 Organisms in bioremediation, 292e295 Organochlorinated pesticides (OC), 41e42, 374 Organochlorines, 41e42, 46 Organophosphate (OP), 41e42 pesticides, 46, 105, 375 Organophosphate degrading (OPD), 168e169 Organophosphorus (OP), 168e169 Oscillatoria sp, 186 Oxalate decarboxylase (ODC), 17 Oxidation, 13, 388 processes, 333e334 Oxidation-reduction potential (ORP), 36 Oxidizing agents, 311e312 Oxidoreductases, 115, 274 EC1, 74 Oxygen, 430 Oxygenases, 136, 275 Ozonation, 10e11, 425

473

474

Index

P p,p dichlorodiphenyldichloroethylene (DDE), 376 p-coumaryl alcohol, 196e197 p-hydroxyphenyl unit, 196e197 P450 monooxygenase, 17 Paecilomyces variotii, 317e320 Pain alleviating drugs. See Nonsteroidal antiinflammatory drugs (NSAIDs) Pantoea agglomerans, 159e160 Panus tigrinus, 204 Paramaecium, 405 Parasitic ligninolytic chemicals, 228 Parasitic organisms, 405 Parawaldeckia karaka, 312 Pathogenic suppression, 401e402 Penicillium, 182, 409 P. chrysogenum, 456 P. citrinum, 317e320 P. rubrum, 160 P. simplicissimum, 335 Pentachlorophenols (PCP), 221e222, 380e381 Perfluorinated compounds, 100, 108e109 Perfluoroalkyl substances, 108 Permethrin, 376 Peroxidases, 115e116, 274e275, 436 degradation and decolorization by, 436e439 HRP, 438e439 lignin peroxidase, 438 manganese peroxidase, 437 Persistent organic pollutants (POPs), 47, 109, 164e166, 176e177, 455 chlorinated ethenes, 166 PAH, 165e166 PCBs and dioxins, 166 Pesticide Data Program (PDP), 41e42 Pesticides, 43, 100, 102e106, 168e169, 221e222, 265, 371e375 impact of, 375e377 biochemical mechanism of pesticides bioremediation, 52e54 biodegradation, 382e389 commonly used pesticide degradation of microorganisms, 388 mechanism of microbial degradation of pesticides, 384e388 microbial degradation of pesticide technology, 388e389 pesticides-degrading microorganism types, 384 carbamate, 375 classification, 43 current scenario, 392e394 effect on environment health, 41e47

factors affect biodegradation, 389e392 environmental factors, 390e391 impact of microorganisms, 392 effect of pesticide structure, 391e392 fate in environment, 43e47 metabolism and degradation of, 378e382 application of adsorbent, 378e382 organochloride, 374 organophosphate, 375 other classes, 375 pesticides-degrading microorganism types, 384 types in agriculture practices, 373te374t Pests, 371 Phaeodactylum tricornutum, 362 Phanerochaete chrysosporium, 16e17, 145, 199e200, 203e204, 223, 226e227, 230, 235, 335e336, 367, 380e381 Pharmaceutical and personal care products (PPCPs), 168 Pharmaceuticals, 70e71, 101e102 biodegradation, 71e72 approaches for pharmaceutical wastes treatment, 72e77 factors affecting biodegradation of, 77e92 PEC oxidation, 88e92 photocatalysis, 78e84 process enhancement conditions, 84e85 recent advancements and approaches, 85e87 Phenerocheate chrysosporium, 228, 231e232 Phenolic compounds, induction of, 208e209 1,4-phenylenediamine, 3 Phlebia P. radiata, 274e275 P. tremellosa, 203e204 Phosphorus, 305 Photocatalysis, 12, 78e84 Photocatalytic oxidation (PC oxidation), 88 Photocatalytic treatment, 311e312 Photoelectro Fenton (PEF), 91 Photoelectrocatalytic oxidation (PEC oxidation), 88e92 Phragmites australis, 312 Phthalate esters (PEs), 106 degradation pathways and metabolic residues of, 111e112 aerobic degradation, 112 anaerobic degradation, 112 metabolic pathway of, 113f Phthalates, 100 Phycoremediation of tannery wastewater constituents, 317 Physical methods, 4e8, 424e426

Index

adsorption, 5e7 coagulation and flocculation, 7e8 Physicochemical methods, 181, 256, 333e334, 419 for tannery wastewater, 308e310 Physicochemical remediation of tannery wastewater constituents, 310e312 Physio-chemical treatment, 128e129 Phytoremediation, 31e32, 116 rhizoremediation, 31e32 Phytostabilization, 31 Pichia anemala, 145 Pigment dyes, 355e356 Pigmentiphaga kullae, 428 Pigments, 1e2, 355 Pithophora sp., 141e142 Plants biomass, 195 heavy metals toxicity in, 248 peroxidises, 436 Plasmodium, 405 Plasticizers, 106e107 Plastics, 408, 454e455 Pleorutus P. eryngii, 205e206, 335 P. flabellatus, 33t P. ostreatus, 33t P. ostreatus, 145, 231e232, 367 HAAS, 258 P. pulmonarius, 33t Pollutants, 450 Pollution, 1e2 Poly-aluminum ferric chloride (PAFC), 310e311 Polyaromatic hydrocarbon (PAH), 455 Polybrominated biphenyl esters (PBEs), 48e50 Polybrominated diphenyl ethers (PBDE), 107 Polychlorinated biphenyls (PCBs), 165e166, 221e222 Polychlorinated dibenzo-p-dioxins and difurans (PCDD/Fs), 165 Polychlorinated ethenes (PCEs), 165 Polycyclic aromatic hydrocarbons (PAH), 135e136, 164e166, 228, 335e336, 382 Polyfluoroalkyl substances (PFAS), 108 Polyhydroxyalkanoates (PHA), 207, 212e213 Polymeric adsorbents, 379 Polymerization in polymer ventures, 231 Polymers, 48e50 polymerization in polymer ventures, 231 Polyphenols, 176e177 Polyvinyl alcohol (PVA), 334e335 Polyvinyl chloride (PVC), 106

Porous activated carbon (PAC), 81 Post-tanning process, 303 Postia placenta, 200e201 Powdered activated carbon (PAC), 6e7 Precipitation, 310e311 Primary substrate, 71 Process enhancement conditions, 84e85 Proteus sp., 15, 136, 426 Protozoa, 405 Pseudochrobactrum mendocina, 455 NR802, 166e167 Pseudochrobactrum saccharolyticum sp., 455 LY10 sp., 166e167 Pseudomonas sp., 15, 30e31, 54, 71e72, 159e160, 164e165, 182e183, 186, 201e202, 231, 259, 266e268, 367, 426, 450 P. aeruginosa, 136, 159e160, 167, 274e275, 313 redox mediators in environmental bioremediation, 272 strain BCH, 366 P. desmolyticum, 366 P. fluorescence Pf-5, 206 P. luteola, 167 P. nitroreducens AR-3, 54 P. paucimobilis SYK-6, 235e236 P. pickettii, 380e381 P. pseudomallei 13 NA, 145 P. putida, 3, 136, 275, 288 P8, 15e16 strain DY1, 167 Pyocyanin-assisted Pseudomonas IEET, 272e273

Q Quorum sensing (QS), 154, 157, 293, 449 in pollutant degradation, 456

R Radioactive waste, 410 Radionuclides bioremediation of, 295e297 microbial interactions with, 289e292 Ralstonia metalliudurans, 32 Raman spectroscopy (RS), 80 Reactive black5, 8 Reactive dyes, 130, 355e356, 419, 422 Reactive oxygen species (ROS), 13 Reactive Red 180, 8 Reactiveorange16, 8 Recalcitrant polyaromatic hydrocarbons, removal of, 229e230 Recycling of waste, 402

475

476

Index

Red blood cells (RBCs), 25 Redox enzymes, electrochemical characterization of, 277e281 Redox mediators (RM), 267e268 of Pseudomonas aeruginosa, 272 Reduced graphene oxide (rGO), 82 Remediation, 175e176, 451 Renewable energy sources, 195 Response surface methodology (RSM), 90 Retro virus, 404e405 Reverse osmosis (RO), 9, 310e311, 359, 425 Rhabdobacter sp., 15, 426 Rhizobium, 15, 178e179, 403, 426 Rhizophoreic microbes, 190e191 Rhizopus R. arrhizus, 381 R. stolonifer, 258 Rhizoremediation, 31e32 metal resistance mechanisms, 32 Rhodobacter sphaeroides, 295, 428 Rhodococcus, 164e165, 209e212, 266 R. jostii RHA1, 213 R. opacus, 291 R. rhodochrous, 291 Rhodopseudomonas palustris, 295 Rhodotorula mucilanginosa, 258 Rhus glabra. See Smooth sumac (Rhus glabra) Rhus vernicifera, 224 Riboflavin (RF), 270 RNA virus, 404e405 Roseobacter, 453e454 Rotating Biological Contractor biofilm process (RBC biofilm process), 75 Rubber rabbitbrush (Ericameria nauseosa), 355 Rumex hymenosepalus. See Canaigre dock (Rumex hymenosepalus) Runoff, 44

S Sabouraud dextrose broth (SDB), 32 Saccharomyces cerevisiae, 16, 427 Safe Drinking Water Act, 106 Sandolan Yellow, 419 Sanguinaria canadensis. See Bloodroot (Sanguinaria canadensis) Sarcosphaera coronaria, 294 Sargassum, 141e142 S. natans, 294e295 S. vulgare, 294e295 Saturated fatty acids, 275 Scanning electron microscope (SEM), 80 Scenedesmus

S. obliquus, 362 S. officinalis, 362 S. quadriquada, 362 Sctyalidium, 182 Senorhizobium, 403 Sequencing batch reactors (SBRs), 75 Serratia, 182e183 S. marcescens, 231, 274e275, 312e313 Sewage treatment, 178 Sewage treatment plants, 69e70 Shewanella, 267e268 S. oneidensis MR-1, 269e270 respiratory complexes of, 270e272 Shewanella algae (SAL), 346 Silica gel, adsorption by, 7 Single photon emission computer tomography imaging techniques (SPECT imaging techniques), 288 Single-walled carbon nanotubes (SWCNTs), 382 Sinorhizobium, 178e179 Smooth sumac (Rhus glabra), 355 Sodium hypochlorite, 11e12 ion exchange, 12 Soil treatment, 178e179, 233e234 Sol-gel method, 80 Sol-thermal method, 80 Solid carrier medium (SSM), 349e350 Solid retention time (SRT), 77 Solid waste management practices, 323 Solvents, 48e50 dyes, 131, 423 Soybean peroxidase (SBP), 436 Spectropotentiostatic techniques, 279e280 Sphaerotilus natans, 33t Sphingomonas, 159e160, 182e183 Spirogyra S. hyalina, 294e295 S. rhizopus, 141e142 Spiruliina platensis, 34 Staphylococcus sp, 15, 266, 426 S. aureus, 167, 313, 428 Stenotrophomonas, 30e31 S. maltophilia, 54, 366 Stereum ostrea, 207 Streptomyces, 201e202, 259 S. alanosinicus, 384 S. atratus, 384 S. cyaneus, 228 S. viridosporus, 203e204, 228 T7A, 231 Streptoverticillium album, 384

Index

Strychoros nuxmonica, 371 Sulfamethoxazole (SMX), 80 Sulfur blue 15, 136 Sulfur dyes, 131, 355e356 Sumithrin, 376 Superoxide scavengers, 84 Surface proteins, 156 Synapyl alcohol, 196e197 Synechococcus, 35 Synthetic dyes, 1e2, 127e128, 166e167, 329e330, 332, 355e356, 433e434 Synthetic laccase mediators, 205e206 Synthetic pyrethroids, 376

T Tanneries, 303e305 Tannery dye, 359 Tannery wastewater challenges and limitations to biological wastewater treatment methods, 320e321 characteristics of, 305, 306t environmental and health impacts, 305e307 metagenomic approach for bioprospecting potential microbes and enzymes, 321e322 microbial biosensors for detection and monitoring of contaminant, 322e323 solid waste management practices, 323 wastewater treatment methods adopted in tanneries, 308e312 Tannins, 176e177 Tat secretion mechanism, 206e207 Technetium (Tc), 288 Temperature, 37 2,2,6,6-tetramethyl-1 piperidinyloxy (TEMPO), 205e206 Textile dyes advanced oxidation process, 13e14 biological methods, 14e18 chemical methods, 9e12 decolorization using various biological treatment options, 133f dye types and toxicity, 2e4 emerging physical method for textile dye effluents treatment, 8 biosorption, 8 and impact on environment, 131e134 membrane technology, 8e9 methods for treatment, 134 methods of dye removal, 333e350 biological methods, 334e350 physicochemical methods, 333e334

physical methods, 4e8 recent biochemical trend, 12 photocatalysis, 12 types and characteristics of dyes, 332 Textile effluents containing azo dyes impact on environment, 357 Textile industry, 423 effluent, 419 Textile wastewater, 127 remediation, 128e129 Textiles industries, 245 Thermobifida fusca, 228 Thermus thermophilus, 228 Thiobacillus T. cuprinicus, 182 T. ferroxidans, 182 T. thioxoxidans, 182 Thlaspi caerulescens, 295 TNT, 221e222 Total dissolved solids (TDS), 72e73 Total Kjeldahl nitrogen (TKN), 305 Total organic carbon (TOC), 87, 305 Total suspended solids (TSS), 317e320 Toxic minerals, 405e406 Toxicity dye types and, 2e4 of heavy metals, 243 Trametes T. gallica, 205e206 T. hirsuta, 205e206 T. hirsute, 231 T. ochracea, 205e206 T. versicolor, 16e17, 199e200, 203e207, 225, 231e233, 276 T. villosa, 205e206 Transgenic technology application, 388e389 Transmission electron microscope (TEM), 80 Treatment strategies, 401e402 Tremera fuciformis, 29 1,1,1-trichloro-2,2-bis(4-chlorophenyl) ethanes (DDT), 221e222 Trichoderma, 182, 409 T. harzianum, 135e136, 335e336 T. viride, 317e320 Trichosporon T. beigelii, 16 T. cutaneum, 209e212 Trypanosoma, 405 Turnip peroxidase (TP), 436 Typha domingensis, 312

477

478

Index

U Ultrafiltration (UF), 9, 425 Ultrapure (UW), 86 Ultrasound treatment, 311e312 Ulva lactuca, 141e142 Unsaturated fatty acids, 275 Upflow anaerobic sludge blanket reactor (UASBR), 75e76 Upflow anaerobic stage reactor (UASR), 76 Urbanization, 175, 265, 329

V Value-added bioproducts lignin bioconversion to, 209e214 microbial lipids, 209e212 muconic acid, 214 polyhydroxyalkanoates, 212e213 vanillin, 213 Van der Waals forces, 156 Vanillin, 213 Vat dyes, 4, 131, 355e356, 422. See also Textile dyes VC. See Cyclic voltammetry (VC) Vector-borne diseases, 372e373 Veratryl alcohol (VA), 203e204 Versatile peroxidase (VP), 199e200, 205 Vibrio fischeri, 81e82, 167 Violuric acid (VLA), 205e206 Viruses, 402, 404e405 Volatile organic compounds (VOCs), 184e185

W Waste generation, 175 improper management of, 175 microorganisms for waste management, 177e179, 406e410 treatment, 371e372 types and sources, 176e177 Wastewater (WW), 86, 153, 232e233 microbial cells and enzymes in, 112e117 treatment methods adopted in tanneries, 308e312 biological treatment or bioremediation of tannery wastewater, 312 microbial remediation, 312e320 physicochemical remediation of tannery wastewater constituents, 310e312 treatment using microbes, 186e189 algae, 186

bacteria, 186 fungi, 189 wastewater-containing dye, 329e330 Wastewater treatment plants (WWTP), 77, 102e105 Water, 305e307 bodies, 401e402 matrix, 81 pollution, 329 water-soluble fiber dyes, 330 Wet chemical deposition. See Sol-gel method Wet fabric production, 329 White-rot fungi (WRF), 16e17, 196, 199e200, 222 degradation with, 16e17 enzyme system of, 17e18 laccases, 18 LiPs, 17 MnPs, 17e18 ligninolytic system of, 221e222 Wood chips, adsorption by, 7 Wood-degrading fungi, 205e206 World Health Organization (WHO), 131

X X-ray diffraction (XRD), 80 Xanthomonas sp., 450 Xenobiotics, 221e222 compounds, 165 Xenophilus sp, 15, 426 X. azoreans, 428 Xylanase, 223

Y Yeast decolorization, 427 degradation with, 16 Yeast peptone glucose (YPG), 32

Z Zetaproteobacteria, 453e454 Zinc, 245, 287e288 Ziram, 375 Zoogloea ramigera, 159e160, 403