Bioresources and Environmental Biotechnology Laboratory, Depar...

Azo dyes account for 70 of the global industrial demand 9 million tons Owing to their genotoxic carcinogenic potential the annual disposal of 4 500 000 tons of dyes and or degraded products is an environmental and socio-economic concern In comparison to physico-chemical methods microbe-mediated dye degradation is considered to be low-input cost-effective and environmentally-safe However under different environmental conditions interactions of chemically diverse dyes with metabolically diverse microbes produce metabolites of varying toxicity In addition majority of studies on microbial dye-degradation focus on decolorization with least attention towards detoxification Therefore the environmental significance of microbial dye detoxification research of past 3 decades is critically evaluated with reference to dye structure and the possible influence of microbial interactions in different environments In the absence of ecosystem-based studies the results of laboratory-based studies on dye degradation metabolite production and their genotoxic impact on model organisms are used to predict the possible fate and consequences of azo dyes metabolites in the environment In such studies the predominance of fewer numbers of toxicological assays that too at lower levels of biological organization molecular cellular organismic suggests its limited ecological significance Based on critical evaluation of these studies the recommendations on inclusion of multilevel approach assessment at multiple levels of biological organization multispecies microcosm approach and native species approach in conjunction with identification of dye metabolites have been made for future studies Such studies will bridge the gap between the fundamental knowledge on dye-microbe-environment interactions and its application to combat dye-induced environmental toxicity Thus an environmental perspective on dye toxicity in the background of dye structure and effects of environmental processes has been developed Based on past 3 decades of research on microbial dye detoxification the current state of knowledge has been analyzed environmental relevance of these studies was ascertained research gaps in microbe-mediated azo dye detoxification have been identified and a research framework emphasizing a better understanding of complex interactions between dye-microbe and environmental processes has been proposed It provides directions for undertaking environmentally sound microbial dye detoxification research Copyright 2016 Elsevier Ltd All rights reserved

Bioresources and Environmental Biotechnology Laboratory, Department of Environmental Studies, University of Delhi, Delhi 110 007, India.

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Detoxification of azo dyes in the context of environmental processes.