Aim The aim of the study is to investigate the efficiency of Geotrichum candidum in the decolourization and mineralization of synthetic azo dyes. Methods and Results It includes screening of enzymes from G. candidum and its optimization, followed by decolourization and mineralization studies. Decolourization was observed to be maximum in methyl orange (94·6%) followed by Congo red (85%), trypan blue (70·4%) and Eriochrome Black T (55·6%) in 48 h, suggesting the plausible degradation of the azo dyes by G. candidum. The enzyme activity study showed that DyP‐type peroxidase has highest activity of 900 mU ml−1 compared to that of laccase (405 mU ml−1) and lignin peroxidase (LiP) (324 mU ml−1) at optimized pH (6) and temperature (35°C). Moreover, the rate of decolourization was found to be directly proportional to the production of laccase and LiP, unlike DyP‐type peroxidase. Furthermore, mineralization study demonstrated reduction in aromatic amines, showing 20% mineralization of methyl orange. Conclusion Geotrichum candidum with its enzyme system is able to efficiently decolourize and mineralize the experimental azo dyes. Significance and Impact of the Study The efficient decolourization and mineralization of azo dyes makes G. candidum a promising alternative in the treatment of textile effluent contaminated with azo dyes.

Currently, globalization, urbanization and industrialization have led to several environmental issues. In many industries, particularly in textile industries, the extensive use of synthetic dyes has increased. Dye is an integral element used to impart color to textile materials. Wastes generated during the processing and treatment of the dye contain inorganic and organic compounds that are hazardous, thereby posing a serious threat to the ecosystem. It is therefore important to implement cost-efficient and successful measures against these emissions in order to preserve habitats and natural resources. In this context, biodegradation by fungi or mycoremediation of dyes using potential fungi is a fairly inexpensive and environmental friendly method for decomposing or mineralizing barely or less decaying dye compounds. Fungi play a crucial role in degrading and decolorizing organic dyes by enzymes and processes such as absorption, adsorption and aggregation of effluent colorants. The factors affecting the decolorization and biodegradation of dye compounds through fungal bioremediation, such as pH, temperature, dye concentration, agitation, effects of carbon and nitrogen sources, dye structure, enzymes, electron donor and redox mediators are discussed in this review. The review also includes a summary on the mechanism and kinetics of dye degradation as well as recent advances and future perspectives in mycoremediation of dyes.

Textile effluent is generally complicated to manage because of its extremely noxious and recalcitrant coloured compositions. Mycoremediation is an extensively used strategy for the competent degradation of hazardous pollutants present in textile effluent. Fungus could be immobilized in synthetic or natural matrices. The current study shows the decolourization of the textile effluent by 85·5 and 98·5% within 6 h using suspended and immobilized fungus, Geotrichum candidum with optimized parameters like inoculum size (5%), pH (4·5), and temperature (30°C). To maintain a high biomass of fungal population and enhance the retention of fungal strain in the contaminated sites, the fungi need to be immobilized. Hence, the fungus was immobilized naturally onto the selected inert support that is, coconut fibres by the means of adsorption, where they grew as active films on the fibres after being grown in the culture broth. The optimized process parameters of inoculum size, fibre quantity and agitation speed for immobilized G. candidum were 5%, 2·2 g l−1 of effluent and 100 rev min−1 respectively. High level of laccase (22 and 25 U l−1 in suspended and immobilized fungal cells treatment respectively) was observed during the process of decolourization and it was found that decolourization was directly proportional to the laccase activity. The UV–vis, FTIR, 1H NMR and GC‐MS analyses of treated textile industrial wastewater revealed the degradation of toxic pollutants in the textile effluent and formation of lower molecular weight intermediates. The study revealed a higher efficacy of immobilized G. candidum in comparison to suspended fungal culture, employing ligninolytic enzyme laccase, which catalyzes the degradation/transformation of aromatic dyes in the textile effluent thus decolourizing it.

The exogenous lipolytic activities of Kocuria sp. have been recognized earlier but the genus further contains many more unexplored strains. In this study, the extracellular lipase activity of Kocuria flava Y4 (GenBank accession no. MT773277), isolated from Dioscorea villosa during our previous study, was regulated by different physicochemical parameters, such as pH, temperature, shaking speed, and incubation time. For efficient immobilization of the extracellular lipase, 4% sodium alginate, 50 mL of 25 nM CaCl2.2H2O solution, and 15 min. Hardening time of gel beads in calcium chloride was used. For the first time, K. flava Y4 lipase was purified using ammonium sulphate precipitation followed by dialysis and DEAE-Sepharose anion exchange chromatography with Sepharose-6B gel filtration chromatography, yielding ∼15-fold purified lipase with a final yield of 96 U/mL. The SDS-PAGE of purified lipase displayed a single strong band, indicating a monomeric protein of 45 kDa. At a temperature of 35°C and pH 8, the purified lipase showed maximum hydrolytic activity. Using p-nitrophenyl acetate (p-NPA) as the hydrolysis substrate, the values of Km and Vmax derived from the Lineweaver–Burk plot were 4.625 mM and 125 mol/min−1mg−1, respectively.

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