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Azo dyes are extensively used in different industries, pose serious threats to environment and human health. These are synthetic molecules which are complex, persistent, and non-degradable. Discharge of untreated dye contaminated wastewater into ecosystem shows negative effects on environment’s esthetics and aquatic life. Application of different physico-chemical procedures for azo dyes elimination has been addressed by various researchers. However, conventional methods are ineffective to completely eliminate azo dyes from industrial effluents because of the high stability and recalcitrant nature of azo dyes. Microbes like bacteria and fungi secrete laccases, peroxidases, and azoreductase, which can efficiently decolorize azo dyes laden wastewater within a shorter time frame. Due to the high efficiency, cost-effective, and non-hazardous nature of biological remediation of dyes, there is an increasing trend of using microbes or microbial enzymes. The present review highlights adverse effects of azo dyes on ecosystem and application of bacteria and fungi as promising candidates for azo dye degradation. The impact of various physical factors, such as pH, temperature, inoculum size, initial dye concentration, availability of nutrients on microbial azo dye degradation have also been reviewed. Both fungi and bacteria have been found safe, efficient, and sustainable tools for azo dye degradation. However, synergistic interactions of microbes effectively utilize diverse metabolic pathways and enzymatic activities, resulting in higher dye degradation efficiency as compared to single microbial species. Further investigations are necessary to identify potential extremophiles and characterization of their enzymes to determine azo dyes degradation pathways and their application at large scale. Thus, integration of microbes with advanced technologies is needed to expedite efforts for implementation of laboratory findings at industrial scale for achieving sustainable development goals for environment protection.
Tyagi et al. (Mon,) studied this question.