AbstractThe extracellular enzyme production capacity of Pleurotus ostreatus MTCC 142 was investigated for decolorization of crystal violet under solid and submerged conditions. Laccases are the major extracellular lignocellulolytic enzymes produced by fungus. Pleurotus ostreatus provided an effective decolorization of dye at 20 mg/L concentration up to 92%. Mycelial growth was observed maximum on plate for a dye concentration 20 mg/L while lowest on 200 mg/L on day 12, respectively. At all concentrations of dye studied, maximum laccase activity was observed on day 8. For 20 mg/L of dye laccase activity was 133 U/L. The decolorization was attributed to microbial action and without role of pH change; less than 0.4 pH change was observed. Manganese dependent peroxidase activity was 106 U/L, maximum on day 8 incubated with 20 mg/L dye concentration. The present study suggested that the high efficiency decolorization of crystal violet by P. ostreatus was assisted by laccase and manganese-dependent peroxidase activity and can be exploited as a promising in biological treatment of waste water containing crystal violet.