Production of laccase from Pleurotus florida using agro-wastes and efficient decolorization of Reactive blue 198

Pleurotus florida NCIM 1243 produced laccase as the dominant lignolytic enzyme during the dye decolorization. Banana peel was the best substrate for extracellular laccase production under solid state fermentation when compared to mandarin peel and cantaloupe peel. The maximum activity of laccase (5.4 U/g) was detected on the 10 day. The ratio of banana peel : mandarin peel : cantaloupe peel (5:2:3) showed increased production of laccase (6.8 U/g). P. florida produced two extracellular laccase isoenzymes (L1 and L2). The half life of laccase at 60 degrees C was 2 h and at 4 h it retained 25% residual activity. P. florida laccase showed high thermostability and an interesting difference was noticed in the behavior of laccase isoenzymes at different temperature. The L1 isoenzyme of laccase showed remarked thermostability at 60 degrees C in the native PAGE when compared to L2 isoenzyme. The optimum pH, temperature and enzyme concentration for maximum decolorization was found to be 4.5, 60 degrees C and 1.2 U/ml, respectively. Partially purified laccase enzyme showed excellent decolorization activity to Reactive blue 198. The maximum decolorization (96%) was observed at lower dye concentrations (50-100 ppm) which decreased markedly when the dye concentration was increased beyond 150 ppm. The thermostable laccase of P. florida could be effectively used to decolorize the synthetic dyes in the textile effluent and other biotechnological applications.