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A novel laccase-producing white-rot fungus, Marasmius sp. BBKAV79 (Genbank Accession Number-KP455496, KP455497), was isolated and subjected to purification, characterization and dye decolorization study. The purified enzyme was obtained with a specific activity of 0.226 U mg -1 protein and a final yield of 13.5 %. The enzyme was found to be a monomeric protein with a molecular mass of *75 kDa as estimated by non-denaturing polyacrylamide gel electrophoresis (PAGE) and further confirmed with zymogram analysis. The optimal pH and temperature of the laccase was recorded to be 5.5 and 40°C, respectively. The metal ions Hg 2? and Ag ? were found to drastically inhibit the activity of laccase at the rate of 96.6 and 96.5 %, respectively. Nevertheless, Fe 3? was found to inhibit laccase activity at 40 %. Phenylmethanesulfonyl fluoride (PMSF) strongly inhibited the laccase activity, and additives viz, sodium dodecyl sulfate (SDS), hydrogen peroxide (H 2 O 2 ) and sodium chloride (NaCl) were known to follow the earlier pattern of enzyme inhibition. The values of kinetic parameters K m and V max for purified laccase were noted at 3.03 mM and 5 lmol min -1 , respectively, for guaiacol as substrate. The textile dyes were decolorized at a range of 72-76 % and 88-93 % when treated with Marasmius sp. BBKAV79 and purified laccase, respectively. Based on the outcome of the present investigation, it could be, therefore, inferred that laccase isolated from Marasmius sp. BBKAV79 effectively decolorizes the textile dyes; however, the metal ions Hg 2? , Ag ? and Fe 3? and agents like PMSF, SDS, H 2 O 2 and NaCl pose an effective inhibitory potential under specified physicochemical conditions.

White rot fungus Marasmius sp. BBKAV79 (GenBank accession number-KP455496, KP455497) exhibited decolourization and degradation of Navy blue HER dye (concentration 50 mg l) within 24 h under shaking condition. In the present study, various investigated parameters like initial dye concentration, pH, temperature, carbon and nitrogen sources were optimized to develop a faster decolourization process by Marasmius sp. BBKAV79. High-performance liquid chromatography, Fourier transform infrared spectroscopy and gas chromatography and mass spectroscopy analysis of the extracted product confirmed the biodegradation of Navy blue HER. The microbial toxicity and phytotoxicity assay revealed that the degradation of Navy blue HER produced nontoxic metabolites.

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