Document Type: REVIEW PAPER


1 Clinical and Environmental Microbiology Group. University of Cartagena, Faculty of Natural and Exact Sciences, Cartagena, Colombia

2 GIA Environmental Research Group, Faculty of Engineering, Fundación Universitaria Tecnológico Comfenalco, Cartagena, Colombia


BACKGROUND AND OBJECTIVES:The objective of this study isto present a description of the main characteristics of azo dyes and the different treatment methods used to remove them from water. There is a special emphasis given to the benefits associated with biological treatment, predominantly those related to the use of bacteria, which has to do with its competitive advantages over other microorganisms in the dye degradation processes.
METHODS: The topic to be addressed was first defined through workshops with the research group. The literature review was carried out following several inclusion/exclusion criteria: the year of publication, as the selection was limited to studies published between 2010 and 2020, the focus of the investigation, which had to be related to the efficiency of different techniques for the remediation of ecosystems contaminated with azo dyes and, lastly, that the studies also discussed the use of environmental bacteria in dye degradation processes.
FINDING: The efficiency of bacteria to degrade azo dyes ranges from 63-100%, the most efficient being: Marinobacter sp, Sphingobacterium sp, Enterococcus faecalis, Enterococcus casseliflavus. The bacteria that, reportedly, have greater efficiency for simultaneously removing the dye-metal complex are Bacillus circulans and Acinetobacter junii.
CONCLUSION: Traditional strategies for the treatment of effluents contaminated with azo dyes are limited to physical and chemical processes that have a high energy and economic cost. For these reasons, current challenges are focused on the use of environmental bacteria capable of transforming dyes into less toxic compounds.

Graphical Abstract


➢   The competitive advantages of bacteria to degrade azo dyes are related to their short life cycle, their ability to adapt and their metabolic action;

➢   The bacterial communities present in marine ecosystems are capable of effectively and simultaneously remedying effluents contaminated with azo dyes and heavy metals through mechanisms that involve enzymatic action;

➢   The most efficient bacteria for simultaneously removing the dye-metal complex are Bacillus circulans and Acinetobacter junii.


Main Subjects

Agrawal, S.; Tipre, D.; Patel, B.; Dave, S., (2014). Optimization of triazo acid black 210 dye degradation by providencia sp. SRS82 and elucidation of degradation pathway. Process Biochem., 49(1): 110-119 (10 pages).

Ahmad, A.L.; Harris, W.A.; Ooi, B.S., (2012). Removal of dye from wastewater of textile industry using membrane technology. J. Teknologi., 36: 31-44 (14 pages).

Ahmadi, M.; Jorfi, S.; Kujlu, R.; Ghafari, S.; Soltani, R.; Haghighifard, N., (2017). A novel salt-tolerant bacterial consortium for biodegradation of saline and recalcitrant petrochemical wastewater. J. Environ. Manage., 191: 198-208 (11 pages).

Ajaz, M.; Rehman, A.; Khan, Z.; Nisar, M.A.; Hussain, S., (2019). Degradation of azo dyes by alcaligenes aquatilis 3c and its potential use in the wastewater treatment.  AMB Express., 9:64 (12 pages).

Akbari, A., (2017). Membrane capsules with hierarchical Mg (OH) 2 nanostructures as novel adsorbents for dyeing wastewater treatment in carpet industries. J. Taiwan Inst. Chem. Eng., 70: 391-400 (10 pages).

Akdogan, H.A.; Topuz, M.C.; Urhan, A., (2014). Studies on decolorization of reactive blue 19 textile dye by Coprinus plicatilis. J. Environ. Health Sci., 12: 49 (7 pages).

Al-Amrani, W.A.; Lim, P.E.; Seng, C.E.; Ngah, W.S.W., (2014).  Factors affecting biodecolorization of azo dyes and cod removal in anoxic – aerobic react operated sequencing batch reactor. J. Taiwan Inst. Chem. Eng., 45(2): 609-616 (18 pages).

Almeida, E.J.R.; Corso, C.R., (2014). Comparative study of toxicity of azo dye procion red mx-5b following biosorption and biodegradation treatments with the fungi aspergillus niger and aspergillus terreus. Chemosphere., 112: 317-322 (6 pages).

Ambrósio, S.; Vilar Júnior, J.; Da Silva, C.; Okada, K.; Nascimento, A.; Longo, R., (2012). A biosorption isotherm model for the removal of reactive azo dyes by inactivated mycelia of Cunninghamella elegans UCP542. Molecules., 17:452–62 (11 pages).

Amoozegar, M.A.; Hajighasemi, M.; Hamedi, J.; Asad, S.; Ventosa, A., (2011). Azo dye decolorization by halophilic and halotolerant microorganisms. Ann. Microbiol., 61(2): 217-230 (14 pages).

An, Q.; Cheng, J.; Wang, Y.; Zhu, M., (2020). Performance and energy recovery of single and two stage biogas production from paper sludge: Clostridium thermocellumaugmentation and microbial community analysis. Renew. Energy., 148: 214–222 (9 pages).

Anwar, F.; Hussain, S.; Ramzan, S.; Hafeez, F.; Arshad, M.; Imran, M.; Abbas, N., (2014). Characterization of reactive red-120 decolorizing bacterial strain Acinetobacter junii FA10 capable of simultaneous removal of azo dyes and hexavalent chromium. Water Air Soil Pollut., 225(8): 2017 (16 pages).

Artz, J.; White, S.; Zadvornyy, O.; Fugate, C.; Hicks, D.; Gauss, G.; Peters, J., (2015). Biochemical and structural properties of a thermostable mercuric ion reductase from Metallosphaera sedula. Front Bioeng Biotech., 3: 97 (8 pages).

Asgher, M.; Yasmeen, Q.; Iqbal, H., (2014). Development of novel enzymatic bioremediation process for textile industry effluents through response surface methodology. Ecol. Eng., 63:1-11 (11 pages).

Ayanda, O.S.; Nelana, S.M.; Naidoo, E.B., (2018). Ultrasonic degradation of aqueous phenolsulfonphthalein (PSP) in the presence of nano-Fe/H2O2. Ultrason sonochem., 47: 29-35 (7 pages).

Baccar, R.; Blánquez, P.; Bouzid, J.; Feki, M.; Attiya, H.; Sarra, M., (2011). Decolorization of a tannery dye: from fungal screening to bioreactor application. Biochem. Eng. J., 56(3):184-189 (6 pages).

Bahadur, N., Bhargava, N., (2019). Novel pilot scale photocatalytic treatment of textile and dyeing industry wastewater to achieve process water quality and enabling zero liquid discharge. J. Water Process. Eng., 32:100934 (5 pages).

Bai, Y.N.; Wang, X.N.; Zhang, F.; Wu, J.; Zhang, W.; Lu, Y.Z.; Zeng, R.J., (2020). High-rate anaerobic decolorization of methyl orange from synthetic azo dye wastewater in a methane-based hollow fiber membrane bioreactor. J. Hazard Mater., 121753 (10 pages).

Bharathiraja, B.; Selvakumari, I.; Iyyappan, J.; Varjani, S., (2019). Itaconic acid: an effective sorbent for removal of pollutants from dye industry effluents. Curr. Opin. Environ. Sci. Health., 12: 6-17 (12 pages).

Balapure, K.H.; Jain, K.; Chattaraj, S.; Bhatt, N.S.; Madamwar, D., (2014). Cometabolic degradation of diazo dye-Reactive blue 160 by enriched mixed cultures BDN. J. Hazard Mater., 279: 85-95 (11 pages).

Bazzi, W.; Abou Fayad, A.G.; Nasser, A.; Haraoui, L.P.; Dewachi, O.; Abou-Sitta, G.; Knapp, C., (2020). Heavy metal toxicity in armed conflicts potentiates AMR in A. baumannii by selecting for antibiotic and heavy metal co-resistance mechanisms. Front. Microbiol., 11:68 (12 pages).

Benkhaya, S.; Cherkaoui, O.; Assouag, M.; Mrabet, S.; Rafik, M.; Harfi, A.E.L., (2016). Synthesis of a new asymmetric composite membrane with bi-component collodion: application in the ultra filtration of baths of reagent dyes of fabric rinsing / padding. J. Mater. Environ. Sci., 7(12): 4556-4569 (13 pages).

Bharagava, R.N.; Mani, S.; Mulla, S.I.; Saratale, G.D., (2018). Degradation and decolourization potential of a ligninolytic enzyme producing Aeromonas hydrophila for crystal violet dye and its phytotoxicity evaluation. Ecotoxicol. Environ. Saf., 156:166-175 (10 pages).

Bharathiraja, B.; Selvakumari, I.A.; Iyyappan, J.; Varjani, S., (2019). Itaconic acid: an effective sorbent for removal of pollutants from dye industry effluents. Curr. Opin. Environ. Sci. Health., 12: 6-17 (11 pages).

Bhardwaj, N.; Bhardwaj, S.K.; Mehta, J.; Mohanta, G.C.; Deep, A., (2016). Bacteriophage immobilized graphene electrodes for impedimetric sensing of bacteria (Staphylococcus arlettae). Anal. Biochem., 505:18-25 (8 pages).

Bilal, M.; Iqbal, H.M., (2019). Lignin peroxidase immobilization on ca-alginate beads and its dye degradation performance in a packed bed reactor system. Biocatal. Agric. Biotechnol., 20: 101205 (8 pages).

Britos, C.N.; Gianolini, J.E.; Portillo, H.; Trelles, J.A., (2018). Biodegradation of industrial dyes by a solvent, metal and surfactant-stable extracellular bacterial laccase. Biocatal. Agric. Biotechnol., 14: 221-227 (7 pages).

Brüschweiler, B.J.; Merlot, C., (2017). Azo dyes in clothing textiles can be cleaved into a series of mutagenic aromatic amines which are not regulated yet. Regul. Toxicol. Pharm., 88:214-226 (13 pages).

Butani, S.; Mane, S., (2017). Coagulation/flocculation process for cationic, anionic dye removal using water treatment residuals–a review. Int. J. Sci. Technol. Mange., 6:121-125 (5 pages).

Cai, Z.; Zhang, W.; Ma, J.; Cai, J.; Li, S.; Zhu, X.; Zhao, X., (2015). Biodegradation of azo dye disperse orange S-RL by a newly isolated strain Acinetobacter sp. Srl8. Water Environ. Res., 87(6):516-523 (8 pages).

Cervantes, F.J.; Dos Santos, A., (2011). Reduction of azo dyes by anaerobic bacteria: microbiological and biochemical aspects. Rev. Environ. Sci. Biotechnol., 10: 125-137 (13 pages).

Cesaro, A.; Belgiorno, V.; Siciliano, A.; Guida, M., (2019). The sustainable recovery of the organic fraction of municipal solid waste by integrated ozonation and anaerobic digestion. Resour Conserv Recy., 141:390-397 (8 pages).

Chakraborty, S.; Basak, B.; Dutta, S.; Bhunia, B.; Dey, A., (2013). Decolorization and biodegradation of congo red dye by a novel white rot fungus Alternaria alternata CMERI F6. Bioresour. Technol., 147: 662–666 (5 pages).

Chan, G.F.; Rashid, N.A.A.; Chua, L.S.; Nasiri, R.; Ikubar, M.R.M., (2012). Communal microaerophilic–aerobic biodegradation of amaranth by novel NAR-2 bacterial consortium. Bioresour. Technol., 105: 48-59 (12 pages).

Chellam, S.; Sari, M., (2016). Aluminum electrocoagulation as pretreatment during microfiltration of surface water containing NOM: A review of fouling, NOM, DBP, and virus control. J. Hazard. Mater., 304: 490-501 (12 pages).

Cinperi, N.C.; Ozturk, E.; Yigit, N.O.; Kitis, M., (2019). Treatment of woolen textile wastewater using membrane bioreactor, nanofiltration and reverse osmosis for reuse in production processes. J. Cleaner Prod., 223: 837-848 (12 pages).

Cui, D.; Li, G.; Zhao, D.; Gu, X.; Wang, C.; Zhao, M., (2012). Microbial community structures in mixed bacterial consortia for azo dye treatment under aerobic and anaerobic conditions. J. Hazard. Mater., 221: 185-192 (8 pages).

Da Fontoura, J.; Rolim, G.; Mella, B.; Farenzena, M.; Gutterres, M., (2017). Defatted microalgal biomass as biosorbent for the removal of Acid Blue 161 dye from tannery effluent. J. Environ. Chem. Eng., 5(5): 5076-5084 (9 pages).

Dayi, B.; Kyzy, A.; Akdogan, H., (2019). Characterization of recuperating talent of white-rot fungi cells to dye-contaminated soil/water. Chin. J. Chem. Eng., 27(3): 634-638 (5 pages).

Das, A.; Mishra, S.; Verma, V.K., (2015). Enhanced biodecolorization of textile dye remazol navy blue using an isolated bacterial strain Bacillus pumilus HKG212 under improved culture conditions. J. Biochem. Tech., 6(3): 962-969 (8 pages).

Di Dato, M.; Galešić, M.; Šimundić, P.; Andričević, R., (2019).  A novel screening tool for the health risk in recreational waters near estuary: the carrying capacity indicator. Sci. Total Environ., 694: 133584 (14 pages).

Dicle, A.R.A.R.; Doganli, G.; Sensoy, T.; Bozbeyoglu, N.; Dogan, N., (2014). Investigation of decolorization of reactive violet 5r and remazol brillant orange 3r by bacillus sp. Dt16. J. Appl. Biol. Sci., 8(1): 68-72 (5 pages).

Dolatabadi, M.; Mehrabpour, M.; Esfandyari, M.; Alidadi, H.; Davoudi, M., (2018). Modeling of simultaneous adsorption of dye and metal ion by sawdust from aqueous solution using of ANN and ANFIS. Chemom. Intell. Lab. Syst., 181:72-78 (7 pages).

Dong, H.; Guo, T.; Zhang, W.; Ying, H.; Wang, P.; Wang, Y.; Chen, Y., (2019). Biochemical characterization of a novel azoreductase from Streptomyces sp.: Application in eco-friendly decolorization of azo dye wastewater. Int. J. Biol. Macromol., 140: 1037-1046 (10 pages).

Elfarash, A.; Mawad, A.M.; Yousef, N.M.; Shoreit, A.A., (2017). Azoreductase kinetics and gene expression in the synthetic dyes-degrading Pseudomonas.  Egypt. J. Basic Appl. Sci., 4(4): 315-322 (8 pages).

Elgarahy, A.; Elwakeel, K.; Elshoubaky, G.; Mohammad, S., (2019). Microwave-accelerated sorption of cationic dyes onto green marine algal biomass. Environ. Sci. Pollut. Res., 26(22): 22704-22722 (19 pages).

Eskandari, F.; Shahnavaz, B.; Mashreghi, M., (2019). Optimization of complete RB-5 azo dye decolorization using novel cold-adapted and mesophilic bacterial consortia. J. Environ. Manage., 241: 91-98 (8 pages).

Fajardo, A.S.; Rodrigues, R.F.; Martins, R.C.; Castro, L.M.; Quinta-Ferreira, R.M., (2015).  Phenolic wastewaters treatment by electrocoagulation process using Zn anode. Chem. Eng. J., 275: 331–341 (10 pages).

Federigi, I.; Verani, M.; Donzelli, G.; Cioni, L.; Carducci, A., (2019). The application of quantitative microbial risk assessment to natural recreational waters: A review. Mar. Pollut. Bull., 144: 334-350 (17 pages).

Franciscon, E.; Grossman, M.J.; Paschoal, J.A.R.; Reyes, F.G.R.; Durrant, L.R., (2012). Decolorization and biodegradation of reactive sulfonated azo dyes by a newly isolated Brevibacterium sp. strain VN-15. SpringerPlus., 1(1): 37 (10 pages).

Garg, S.K.; Tripathi, M.; Singh, S.K.; Tiwari, J.K., (2012). Biodecolorization of textile dye effluent by Pseudomonas putida SKG-1 (MTCC 10510) under the conditions optimized for monoazo dye orange II color removal in simulated minimal salt medium. Int. Biodeterior. Biodegrad., 74:24-35 (10 pages).

Ge, L.; Wang, W.; Peng, Z.; Tan, F.; Wang, X.; Chen, J.; Qiao, X., (2018). Facile fabrication of Fe@ MgO magnetic nanocomposites for efficient removal of heavy metal ion and dye from water. Powder Technol., 326: 393-401 (9 pages).

Ghodake, G.; Jadhav, U.; Tamboli, D.; Kagalkar, A.; Govindwar, S., (2011). Decolorization of textile dyes and degradation of mono-azo dye amaranth by Acinetobacter calcoaceticus NCIM 2890. Indian J. Microbiol., 51(4): 501-508 (8 pages).

Ghosh, A.; Ghosh Dastidar, M.; Sreekrishnan, T.R., (2016). Recent advances in bioremediation of heavy metals and metal complex dyes. J. Environ. Eng., 142(9): C4015003-1 (14 pages).

Ghuge, S.; Saroha, A., (2018). Catalytic ozonation of dye industry effluent using mesoporous bimetallic Ru-Cu/SBA-15 catalyst. Process. Saf. Environ., 118:125-132 (8 pages).

Giovanella, P.; Vieira, G.; Otero, I.; Pellizzer, E.; De Jesus Fontes, B.; Sette, L., (2020). Metal and organic pollutants bioremediation by extremophile microorganisms. J. Hazard. Mater., 382: 121024 (14 pages).

Gomes, C.; Piccin, J.; Gutterres, M., (2016). Optimizing adsorption parameters in tannery-dye-containing effluent treatment with leather shaving waste. Process. Saf. Environ., 99: 98-106 (9 pages).

González, R.; Villagómez, R.; Madariaga, A.; Castro, J.; González, C., (2018). Biological Consortia Designed for Laccase Production and Dye Removal. Preprints., 2018040264 (16 pages)

Guadie, A.; Tizazu, S.; Melese, M.; Guo, W.; Ngo, H.; Xia, S., (2017). Biodecolorization of textile azo dye using Bacillus sp. strain CH12 isolated from alkaline lake. Biotechnol. Rep., 15: 92-100 (8 pages).

Guan, R.; Yuan, X.; Wu, Z.; Jiang, L.; Li, Y.; Zeng, G., (2018). Principle and application of hydrogen peroxide based advanced oxidation processes in activated sludge treatment: A review. Biochem. Eng. J., 339: 519-530 (12 pages).

Guo, G.; Li, X.; Tian, F.; Liu, T.; Yang, F.; Ding, K.; Wang, C., (2020). Azo dye decolorization by a halotolerant consortium under microaerophilic conditions. Chemosphere., 244: 125510 (8 pages).

Gupta, V.K.; Khamparia, S.; Tyagi, I.; Jaspal, D.; Malviya, A., (2015). Decolorization of mixture of dyes: A critical review. Global J. Environ. Sci. Manage., 1 (1): 71-94 (24 pages).

Gürses, A.; Açıkyıldız, M.; Güneş, K.; Gürses, M.S., (2016). Dyes and Pigments. Springer, Cham. (83 pages).

Hongsawat, P.; Vangnai, A.S., (2011). Biodegradation pathways of chloroanilines by Acinetobacter baylyi strain GFJ2.J. Hazard. Mater., 186(2-3):1300-1307 (8 pages).

Huang, G.; Wang, W.; Liu, G., (2015). Simultaneous chromate reduction and azo dye decolourization by Lactobacillus paracase CL1107 isolated from deep sea sediment. J. Environ. Manage., 157: 297-302 (5 pages).

Huët, M.A.L.; Puchooa, D., (2017). Bioremediation of heavy metals from aquatic environment through microbial processes: A potential role for probiotics. J. Appl. Biol. Biotechnol., 5(6): 14-23 (10 pages).

Ilnicka, A.; Kamedulski, P.; Aly, H.; Lukaszewicz, J., (2020). Manufacture of activated carbons using Egyptian wood resources and its application in oligothiophene dye adsorption. Arab. J. Chem., 13:5284-5291 (8 pages).

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(1): 73-92 (20 pages).

Jaria, G.; Silva, C.; Ferreira, C.; Otero, M.; Calisto, V., (2017). Sludge from paper mill effluent treatment as raw material to produce carbon adsorbents: an alternative waste management strategy. J. Environ. Manage., 188: 203-211 (9 pages).

Johnson, N.W.; Gedalanga, P.B.; Zhao, L.; Gu, B.; Mahendra, S., (2020). Cometabolic biotransformation of 1, 4-dioxane in mixtures with hexavalent chromium using attached and planktonic bacteria. Sci. Total Environ., 706: 135734 (10 pages).

Kakkar, S.; Malik, A.; Gupta, S., (2018). Treatment of pulp and paper mill effluent using low cost adsorbents: an overview. J. Appl. Nat. Sci.,10:695–704 (10 pages).

Katheresan, V.; Kansedo, J.; Lau, S., (2018). Efficiency of various recent wastewater dye removal methods: a review. J. Environ. Chem. Eng., 6(4): 4676-4697 (22 pages).

Khan, N.; Bhadra, B.; Jhung, S., (2018). Heteropoly acid-loaded ionic liquid@ metalorganic frameworks: effective and reusable adsorbents for the desulfurization of a liquid model fuel. Chem. Eng. J., 334: 2215-2221 (7 pages).

Kim, D.; Jo, W., (2019). Sustainable treatment of harmful dyeing industry pollutants using SrZnTiO3/g-C3N4 heterostructure with a light source-dependent charge transfer mechanism. Appl. Catal B-Environ., 242: 171-177 (7 Pages).

Kertesz, S.; Cakl, J.; Jirankova, H., (2014). Submerged hollow fiber microfiltration as a part of hybrid photocatalytic process for dye wastewater treatment. Desalination. 343: 106-112 (7 pages).

Khadim, H.J.; Ammar, S.H.; Ebrahim, S.E., (2019). Biomineralization based remediation of cadmium and nickel contaminated wastewater by ureolytic bacteria isolated from barn horses soil. Environ. Technol. Innovation., 14: 100315 (10 pages). 

Khalid, A.; Kausar, F.; Arshad, M.; Mahmood, T.; Ahmed, I., (2012). Accelerated decolorization of reactive azo dyes under saline conditions by bacteria isolated from Arabian seawater sediment. Appl. Microbiol. Biotechnol., 96: 1599-1606 (8 pages).

Khan, S.; Malik, A., (2018). Toxicity evaluation of textile effluents and role of native soil bacterium in biodegradation of a textile dye. Environ. Sci. Pollut. Res. Int., 25 (5): 4446-4458 (13 pages).

Khan, Z.; Kunal, M.; Soni, A.; Madamwar, D., (2014). Microaerophilic degradation of sulphonated azo dye Reactive Red 195 by bacterial consortium AR1 through cometabolism. Int. Biodeterior. Biodegrad., 94: 167-175 (9 pages).

Khandare, R.V.; Kabra, A.N.; Tamboli, D.P.; Govindwar, S.P., (2011). The role of Aster amellus Linn. in the degradation of a sulfonated azo dye Remazol Red: a phytoremediation strategy. Chemosphere. 82(8): 1147-1154 (8 pages).

Kumar, V.; Suraj, P.; Ghosh, P., (2019). Optimization of COD Removal by Advanced Oxidation Process through Response Surface Methodology from Pulp & Paper Industry Wastewater.J. Sci. Ind. Res., 78:386-390 (5 pages).

Kuppusamy, S.; Sethurajan, M.; Kadarkarai, M.; Rajasekar, A., (2016). Biodecolourization of textile dyes by novel, indigenous Pseudomonas stutzeri MN1 and Acinetobacter baumannii MN3. J. Environ. Chem. Eng., 5(1): 716-724 (9 pages).

Kurade, M.B.; Waghmode, T.R.; Khandare, R.V.; Jeon, B.H.; Govindwar, S.P., (2016). Biodegradation and detoxification of textile dye Disperse Red 54 by Brevibacillus laterosporus and determination of its metabolic fate. J. Biosci. Bioeng., 121(49): 442-449(8 pages).

Latif, A.; Sheng, D.; Sun, K.; Si, Y.; Azeem, M.; Abbas, A.; Bilal, M., (2020). Remediation of heavy metals polluted environment using Fe-based nanoparticles: Mechanisms, influencing factors, and environmental implications. Environ. Pollut., 114728  (15 pages).

Lee, T.; Pang, S.; Abraham, S.; Coombs, G.W., (2019). Antimicrobial-resistant CC17 Enterococcus faecium: the past, the present and the future. J. Glob. Antimicrob. Resist., 16: 36-47 (12 pages).

Li, Z.; Li, L.; Hu, D.; Gao, C.; Xiong, J.; Jiang, H.; Li, W., (2019). Efficient removal of heavy metal ions and organic dyes with cucurbit [8] uril-functionalized chitosan. 
J. Colloid Interf Sci., 539: 400-413 (
14 pages).

Lin, Y.; Wang, D.; Wang, T., (2012). Ethanol production from pulp & paper sludge and monosodium glutamate waste liquor by simultaneous saccharification and fermentation in batch condition. Chem. Eng., 191: 31–37 (7 pages).

Lin, Y.; Liang, J.; Zeng, C.; Wang, D.; Lin, H., (2017). Anaerobic digestion of pulp and paper mill sludge pretreated by microbial consortium OEM1 with simultaneous degradation of lignocellulose and chlorophenols. Renew. Energy., 108: 108–115 (8 pages).

Liu, S.; Song, H.; Wei, S.; Liu, Q.; Li, X.; & Qian, X., (2015). Effect of direct electrical stimulation on decolorization and degradation of azo dye reactive brilliant red X3B in biofilm-electrode reactors. Biochem. Eng. J., 93:294-302 (9 pages).

Liu, W.; Liu, C.; Liu, L.; You, Y.; Jiang, J.; Zhou, Z.; Dong, Z., (2017). Simultaneous decolorization of sulfonated azo dyes and reduction of hexavalent chromium under high salt condition by a newly isolated salt-tolerant strain Bacillus circulans BWL1061. Ecotox. Environ. Safe., 141: 9-16 (8 pages).

Lončar, N.; Gligorijević, N.; Božić, N.; Vujčić, Z., (2014). Congo red degrading laccases from Bacillus amyloliquefaciens strains isolated from salt spring in Serbia. Int. Biodeterior. Biodegrad., 91:18-23 (6 pages).

Mahmood, S.; Khalid, A.; Mahmood, T.; Arshad, M.; Ahmad, R., (2013). Potential of newly isolated bacterial strains for simultaneous removal of hexavalent chromium and reactive black‐5 azo dye from tannery effluent. J. Chem. Technol. Biotechnol., 88(8): 1506-1513 (8 pages).

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): 639-651 (13 pages).

Martínez-López, S.; Lucas-Abellán, C.; Serrano-Martínez, A.; Mercader-Ros, M.; Cuartero, N.; Navarro, P.; Gómez-López, V., (2019). Pulsed light for a cleaner dyeing industry: Azo dye degradation by an advanced oxidation process driven by pulsed light. J. Clean. Prod., 217: 757-766 (10 pages).

Maqbool, Z., (2016). Characterization and application of dye decolorizing metal tolerant bacterial community for treatment of textile wastewater (Doctoral dissertation, Gc University, Faisalabad) (222 pages).

Martorell, M.; Pajot, H.; De Figueroa; L., (2012). Dye-decolourizing yeasts isolated from Las Yungas rainforest Dye assimilation and removal used as selection criteria. Int. Biodeter. Biodegr., 66:25–32 (8 pages).

Meerbergen, K.; Willems, K.; Dewil, R.; Van Impe, J.; Appels, L.; Lievens, B., (2018). Isolation and screening of bacterial isolates from wastewater treatment plants to decolorize azo dyes. 
J. Biosci. Bioeng., 125(4): 448-456 (
9 pages).

Mincea, M.; Patrulea, V.; Negrulescu, A.; Szabo, R.; Ostafe, V., (2013). Adsorption of three commercial dyes onto chitosan beads using spectrophotometric determination and a multivariate calibration method. J. Water Resour. Prot., 5: 446-457 (12 pages).

Misal, S.; Lingojwar, D.; Shinde, R.; Gawai, K., (2011). Purification and characterization of azoreductase from alkaliphilic strain Bacillus badius. Process. Biochem., 46(6): 1264-1269 (6 pages).

Mittal, H.; Alhassan, S.M.; Ray, S.S., (2018). Efficient organic dye removal from wastewater by magnetic carbonaceous adsorbent prepared from corn starch. J. Environ. Chem. Eng., 6(6): 7119-7131 (13 pages).

Mondal, P.; Baksi, S.; Bose, D., (2017). Study of environmental issues in textile industries and recent wastewater treatment technology. World Sci. News., 61 (2): 98-109 (12 pages).

Morais, I.; Silva, C.; Borges, C., (2016). Aerobic granular sludge to treat paper mill effluent: organic matter removal and sludge filterability. Desalin. Water Treat., 57: 8119–8126 (8 pages).

Nanda, M.; Kumar, V.; Sharma, D.K., (2019). Multimetal tolerance mechanisms in bacteria: The resistance strategies acquired by bacteria that can be exploited to 'clean-up' heavy metals contaminants from water. Aquat. Toxicol., 212: 1-10 (10 pages).

Ngulube, T.; Gumbo, J.R.; Masindi, V.; Maity, A., (2017). An update on synthetic dyes adsorption onto clay based minerals: a state-of-art review. J. Environ. Manage., 191:35–57 (23 pages).

Ning, X.; Yang, C.; Wang, Y.; Yang, Z.; Wang, J.; Li, R., (2014). Decolorization and biodegradation of the azo dye Congo red by an isolated Acinetobacter baumannii YNWH 226. Biotechnol. Bioproc. Eng., 19(4): 687-695 (9 pages).

Oon, Y.S.; Ong, S.A.; Ho, L.N.; Wong, Y.S.; Oon, Y.L.; Lehl, H.K.; Nordin, N., (2017). Microbial fuel cell operation using monoazo and diazo dyes as terminal electron acceptor for simultaneous decolourization and bioelectricity generation. J. Hazard. Mater., 325: 170-177 (8 pages).

Orts, F.; del Río, A.I.; Molina, J.; Bonastre, J.; Cases, F., (2018). Electrochemical treatment of real textile wastewater: Trichromy Procion HEXL®. J. Electroanal. Chem., 808: 387-394 (8 pages).

Oturkar, C.; Patole, M.S.; Gawai, K.R.; Madamwar, D., (2013). Enzyme based cleavage strategy of Bacillus lentus BI377 in response to metabolism of azoic recalcitrant. Bioresour. Technol., 130: 360-365 (6 pages).

Öztürk, A.; Bayol, E.; Abdullah, M., (2020). Characterization of the biosorption of fast black azo dye K salt by the bacterium Rhodopseudomonas palustris 51ATA strain. Electron. J. Biotechnol., 46: 22-29 (8 pages).

Pavithra, K.G.; Jaikumar, V., (2019). Removal of colorants from wastewater: A review on sources and treatment strategies. J. Ind. Eng. Chem., 75:1-19 (19 pages).

Pietruk, K.; Piątkowska, M.; Olejnik, M., (2019). Electrochemical reduction of azo dyes mimicking their biotransformation to more toxic products. J. Vet. Res., 63(3): 433-438 (6 pages).

Pourrahim, S.; Salem, A.; Salem, S.; Tavangar, R., (2020). Application of solid waste of ductile cast iron industry for treatment of wastewater contaminated by reactive blue dye via appropriate nano-porous magnesium oxide. Environ. Pollut., 256: 113454 (10 pages).

Prasad, A.A.; Satyanarayana, V.S.V.; Rao, K.B., (2013). Biotransformation of direct blue 1 by a moderately halophilic bacterium Marinobacter sp. strain HBRA and toxicity assessment of degraded metabolites. J. Hazard. Mater., 262: 674-684 (11 pages).

Priya, B.; Uma, L.; Ahamed, A.; Subramanian, G.; Prabaharan, D., (2011).  Ability to use the diazo dye C. I. Acid Black 1 as a nitrogen source by the marine cyanobacterium Oscillatoria curviceps BDU92191. Bioresour. Technol., 102:7218–7223 (5 pages).

Qu, W.; Liu, T.; Wang, D.; Hong, G.; Zhao, J., (2018). Metagenomics-based discovery of malachite green-degradation gene families and enzymes from mangrove sediment. Front. Microbiol., 9: 2373-2382 (10 pages).

Rathod, J.; Dhebar, S.; Archana, G., (2017). Efficient approach to enhance whole cell azo dye decolorization by heterologous overexpression of Enterococcus sp. L2 azoreductase (azoA) and Mycobacterium vaccae formate dehydrogenase (FDH) in different bacterial systems. Int. Biodeterior. Biodegrad., 124: 91-100 (9 pages).

Rehman, K.; Shahzad, T.; Sahar, A.; Hussain, S.; Mahmood, F.; Siddique, M.H., (2018). Effect of Reactive Black 5 azo dye on soil processes related to C and N cycling. PeerJ., 6: e4802. (14 pages).

Rekik, H.; Jaouadi, N.Z.; Bouacem, K.; Zenati, B.; Kourdali, S.; Badis, A.; Jaouadi, B., (2019). Physical and enzymatic properties of a new manganese peroxidase from the white-rot fungus Trametes pubescens strain i8 for lignin biodegradation and textile-dyes biodecolorization. Int. J. Biol. Macromol., 125:514-525 (22 pages).

Ribera Pi, J. (2019). Hybrid systems for wastewater treatment in the framework of circular economy: coupling biological and membrane technologies for a sustainable water cycle (Doctoral dissertation, Universitat Politècnica de Catalunya) (247 pages).

Sabaruddin, M.F.; Nor, M.H.M.; Mubarak, M.F.M.; Rashid, N.A.A.; Far, C.G.; Youichi, S.; Ibrahim, N., (2018). Biodecolourisation of acid red 27 Dye by Citrobacter freundii A1 and Enterococcus casseliflavus C1 bacterial consortium. Mal. J. Fund., 14 (2): 202-207 (6 pages).

Sahasrabudhe, M.M.; Saratale, R.G.; Saratale, G.D.; Pathade, G.R., (2014). Decolorization and detoxification of sulfonated toxic diazo dye CI Direct Red 81 by Enterococcus faecalis YZ 66. J. Environ. Health Sci.,12(1):151 (13 pages).

Saratale, R.G.; Saratale, G.D.; Chang, J.S.; Govindwar, S.P., (2011).; Bacterial decolorization and degradation of azo dyes: a review. J. Taiwan Inst. Chem. Eng., 42(1): 138-157 (20 pages).

Saravanan, C.; Rajesh, R.; Kaviarasan, T.; Muthukumar, K.; Kavitake, D.; Shetty, P.H., (2017). Synthesis of silver nanoparticles using bacterial exopolysaccharide and its application for degradation of azo-dyes. Biotechnol. Rep., 15: 33-40 (8 pages).

Sardar, U.R.; Bhargavi, E.; Devi, I.; Bhunia, B.; Tiwari, O. N., (2018). Advances in exopolysaccharides based bioremediation of heavy metals in soil and water: a critical review. Carbohydr. Polym., 199: 353-364 (12 pages).

Sarkar, S.; Banerjee, A.; Chakraborty, N.; Soren, K.; Chakraborty, P.; Bandopadhyay, R., (2020). Structural-functional analyses of textile dye degrading azoreductase, laccase and peroxidase: A comparative in silico study. Electron. J. Biotechnol., 43: 48-54 (7 pages).

Shah, M., (2014). Effective treatment systems for azo dye degradation: a joint venture between physico-chemical and microbiological process. Int. J. Environ. Bioremediat. Biodegrad., 2(5): 231-242 (12 pages).

Shamraiz, U.; Hussain, R.A.; Badshah, A.; Raza, B.; Saba, S., (2016). Functional metal sulfides and selenides for the removal of hazardous dyes from Water. J. Photochem. Photobiol. B., 159: 33-41 (9 pages).

Sharma, A.; Gupta, G.; Ahmad, T.; Kaur, B.; Hakeem, K.R., (2020). Tailoring cellular metabolism in lactic acid bacteria through metabolic engineering. J. Microbiol. Methods., 170: 105862. (14 pages).

Singh, R.P.; Singh, P.K.; Singh, R.L., (2014). Bacterial decolorization of textile azo dye acid orange by Staphylococcus hominis RMLRT03. Toxicol int., 21(2): 160-166 (7 pages).

Singh, R.L.; Singh, P.K.; Singh, R.P., (2015). Enzymatic decolorization and degradation of azo dyes–A review. Int. Biodeterior. Biodegrad., 104: 21-31 (11 pages).

Singh, G.; Kaur, S.; Khatri, M.; Arya, S., (2019). Biobleaching for pulp and paper industry in India: Emerging enzyme technology.  Biocatal. Agric. Biotechnol., 17: 558-565 (8 pages).

Solano A.M.S.; Garcia-Segura S.; Martínez-Huitle C.A.; Brillas E., (2015). Degradation of acidic aqueous solutions of the diazo dye Congo Red by photo-assisted electrochemical processes based on Fenton's reaction chemistry. Appl. Catal B., 168-169: 559–571 (13 pages).

Solís, M.; Solís, A.; Pérez, H.; Manjarrez, N.; Flores, M., (2012). Microbial decolouration of azo dyes: a review. Process Biochem., 47(12): 1723-1748 (26 pages).

Soni, R.; Bhatt, N.S.; Modi, H.A.; Acharya, P.B., (2016). Decolorization, degradation and subsequent toxicity assessment of reactive red 35 by Enterococcus gallinarum. Curr. Biotechnol., 5(4): 25-336 (12 pages).

Sun, J.;  Kweon, O.;  Jin, J.; He, G.X.; Li, X.; Cerniglia, C.E.; Chen, H., (2017). Mutation network-based understanding of pleiotropic and epistatic mutational behavior of Enterococcus faecalis FMN-dependent azoreductase. Biochem. Biophys., 12: 240-244 (5 Pages).

Talaiekhozani, A.; Mosayebi, M.; Fulazzaky, M.; Eskandari, Z.; Sanayee, R., (2020). Combination of TiO2 microreactor and electroflotation for organic pollutant removal from textile dyeing industry wastewater. Alex. Eng. J., 59(2): 549-563 (15 pages).

Talaiekhozani, A.; Rezania, S., (2017). Application of photosynthetic bacteria for removal of heavy metals, macro-pollutants and dye from wastewater: A review. J. Water Process. Eng., 19:312-321 (10 pages).

Tamboli, D.P.; Kagalkar, A.N.; Jadhav, M.U.; Jadhav, J.P.; Govindwar, S. P., (2010). Production of polyhydroxyhexadecanoic acid by using waste biomass of Sphingobacterium sp. ATM generated after degradation of textile dye Direct Red 5B. Bioresour. Technol., 101(7): 2421-2427 (7 pages).

Tee, H.C.; Lim, P.E.; Seng, C.E.; Nawi, M.A.M.; Adnan, R., (2015). Enhancement of azo dye Acid Orange 7 removal in newly developed horizontal subsurface-flow constructed wetland. J. Environ. Manage., 147: 349-355 (7 pages).

Thanavel, M.; Bankole, P.O.; Kadam, S.; Govindwar, S.P.; Sadasivam, S.K., (2019). Desulfonation of the textile azo dye acid fast yellow mr by newly isolated Aeromonas hydrophila sk16. Water Resour. Ind., 22: 100116 (9 Pages).

Thu, W.P.; Sinwat, N.; Bitrus, A.A.; Angkittitrakul, S.; Prathan, R.; Chuanchuen, R., (2019). Prevalence, antimicrobial resistance, virulence gene, and class 1 integrons of Enterococcus faecium and Enterococcus faecalis from pigs, pork and humans in Thai-Laos border provinces. J. Global Antimicrob. Resist., 18:130-138 (9 pages).

Tišma, M.; Šalić, A.; Planinić, M.; Zelić, B.; Potočnik, M.; Šelo, G.; Bucić-Kojić, A., (2020). Production, characterisation and immobilization of laccase for an efficient aniline-based dye decolourization. J. Water Process. Eng., 36: 101327 (9 pages).

Unnikrishnan, S.; Khan, M.H.; Ramalingam, K., (2018). Dye-tolerant marine Acinetobacter baumannii-mediated biodegradation of reactive red. Water Sci. Eng., 11(4): 265-275 (11 pages).

Vignaroli, C.; Pasquaroli, S.; Citterio, B.; Di Cesare, A.; Mangiaterra, G.; Fattorini, D.; Biavasco, F., (2018). Antibiotic and heavy metal resistance in enterococci from coastal marine sediment. Environ. Pollut., 237: 406-413 (8 pages).

Vikrant, K.; Giri, B. S.; Raza, N.; Roy, K.; Kim, K.H.; Rai, B.N.; Singh, R.S., (2018). Recent advancements in bioremediation of dye: current status and challenges. Bioresour. Technol., 253: 355-367 (13 pages).

Vuthiganond, N.; Nakpathom, M.; Mongkholrattanasit, R., (2018). Metal-free dyeing of cotton fabric using mangrove bark polyphenols via azoic dyeing. Fibers Polym., 19(12): 2524-2532 (9 pages).

Walter, T.; Klim, J.; Jurkowski, M.; Köhling, I.; Słodownik, M.; Zielenkiewicz, U., (2020). Plasmidome of an environmental Acinetobacter lwoffii strain originating from a former gold and arsenic mine. Plasmid., 110: 102505 (17 pages).

Wang, N.; Chu, Y.; Wu, F.; Zhao, Z.; Xu, X., (2017). Decolorization and degradation of congo red by a newly isolated white rot fungus, Ceriporia lacerata, from decayed mulberry branches. Int. Biodeter. Biodegr. 117: 236–244 (8 pages).

Wang, Y.; Jiang, L.; Shang, H.; Li, Q.; Zhou, W., (2020). Treatment of azo dye wastewater by the self-flocculating marine bacterium Aliiglaciecola lipolytica. Environ. Technol. Inno., 19: 100810 (12 pages).

Wardman, R.H., (2017). An introduction to textile coloration: principles and practice. Hoboken, N.J: John Wiley Sons. (376 pages).

Wu, Y.; Li, T.; Yang, L., (2012). Mechanisms of removing pollutants from aqueous solutions by microorganisms and their aggregates: a review. Bioresour. Technol., 107: 10 -18 (9 pages).

Wu, J.W.; Wu, C.R.; Zhou, C. S.; Dong, L.L.; Liu, B.F.; Xing, D.F.; Yang, S.S.; Fan, J.N.; Feng, L. P.; Cao, G.L.; You, S.J., (2020). Fate and removal of antibiotic resistance genes in heavy metals and dye co-contaminated wastewater treatment system amended with β-cyclodextrin functionalized biochar.  Sci. Total Environ., 723: 137991 (8 pages).

Xie, W.; Pakdel, E.; Liang, Y.; Liu, D.; Sun, L.; Wang, X., (2020). Natural melanin/TiO2 hybrids for simultaneous removal of dyes and heavy metal ions under visible light. J. Photochem. Photobiol., 389: 112292 (10 pages).

Xu, F.; Mou, Z.; Geng, J.; Zhang, X.; Li, C., (2016). Azo dye decolorization by a halotolerant exoelectrogenic decolorizer isolated from marine sediment. Chemosphere., 158: 30-36 (7 pages).

Yagub, M.; Sen T.K.; Afroze, A.; Ang, H., (2014). Dye and its removal from aqueous solutions by adsorption: A review. Adv. Colloid Interface Sci., 209: 172-184 (13 pages).

Yang, S.; Li, W.; Zhang, H.; Wen, Y.; Ni, Y., (2019). Treatment of paper mill wastewater using a composite inorganic coagulant prepared from steel mill waste pickling liquor. Sep. Purif. Technol., 209: 238-245 (8 pages).

Zhang, J.; Zeng, Y.; Liu, B.; Deng, X., (2020). MerP/MerT-mediated mechanism: a different approach to mercury resistance and bioaccumulation by marine bacteria. J. Hazard. Mater., 388: 122062 (10 pages).

Zhang, L.; Pan, J.; Liu, L.; Song, K.; Wang, Q., (2019). Combined physical and chemical activation of sludge-based adsorbent enhances Cr (Ⅵ) removal from wastewater. J. Cleaner Prod., 238: 117904 (9 pages).

Zhao, B.; Shang, Y.; Xiao, W.; Dou, C.; Han, R., (2014). Adsorption of Congo red from solution using cationic surfactant modified wheat straw in column model. J. Environ. Chem. Eng., 2: 40-45 (6 pages).

Zhong, C.; Sun, S.; Zhang, D.; Liu, L.; Zhou, S.; Zhou, J., (2020). Production of a bioflocculant from ramie biodegumming wastewater using a biomass-degrading strain and its application in the treatment of pulping wastewater. Chemosphere., 253: 126727 (9 pages).

Zhuang, M.; Sanganyado, E.; Li, P.; Liu, W., (2019). Distribution of microbial communities in metal-contaminated nearshore sediment from Eastern Guangdong, China. Environ. Pollut., 250: 482–492 (11 pages).

Zhuang, M.; Sanganyado, E.; Zhang, X.; Xu, L.; Zhu, J.; Liu, W.; Song, H., (2020). Azo dye degrading bacteria tolerant to extreme conditions inhabit nearshore ecosystems: Optimization and degradation pathways. J. Environ. Manage., 261: 110222 (23 pages).

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