LAUSR

Abstract Managing triphenylmethane class of dyes such as aniline blue present in the effluents is a nightmare for the industries and environmentalists. There are physical and chemical approaches available for degrading these recalcitrant dyes. However, these methods become expensive process and also degraded products are not eco-friendly in nature. Laccase from white rot fungi had been used for biotransformation of triphenylmethane class of dyes except for aniline blue. This study focussed on laccase from gamma irradiated endophytic fungus (Phomopsis sp.) and its enhanced activity in degrading aniline blue as well as textile dye effluent. Laccase production was increased in 1.2 kGy gamma irradiated endophytic fungus (2 fold) and hence dye degradation was enhanced when compared to the non-irradiated (wild) fungus. The laccase activity exhibited appreciable stability for metal ions (Zn2+, Cu2+, Cr2+ and Ca2+) up to 10 mM concentration. The highest laccase activity and dye decolourisation rate was observed around 30°C temperature at pH 5. The degraded intermediates were identified and a mechanism of degradation was proposed based on UV-Visible, FTIR and LC-MS analysis. The aniline blue degradation kinetics strictly followed Michaelis-Menten model. The degraded aniline blue dye samples had reduced COD and were non-toxic to plants and microorganisms. To substantiate the industrial application, textile effluent was treated with laccase from the endophytic fungus and found 99% decolourisation within 2.5 hours. There was a 67% reduction in COD and a 47% reduction in BOD in laccase mediated textile effluent treatment.