Studies on production and evaluation of biopigment and synthetic dye decolorization capacity of laccase produced by A. oryzae cultivated on agro-waste.

The present study investigated the screening of mono and co-culture fungal cultivations for laccase production using extracted lignin as the substrate obtained from cauliflower wastes by two different pretreatment methods. Amongst mono and mixed culture fungal cultivations, monoculture of Aspergillus oryzae exhibited the highest enzymatic activity of 29.7 ± 0.6 U mL-1 under submerged conditions and using alkali extracted lignin as substrate. Under the optimal conditions (pH 4.5, 30 °C, 12 days, 1% (w/v) lignin and 0.5 mM Cu2+ concentration) the maximum laccase activity was estimated to be 41.3 ± 2.8 U mL-1 and production yield of 153.3 ± 2.4 mg L-1. Maximum decolorization of pigment extracted from Aspergillus heteromorphus CBS 117.55 cultivated culture media was achieved by administration of 40 U g-1 of crude enzyme concentration. Thermal and pH stability of crude laccase was observed over wide ranges. The dye decolorization efficiency of crude A. oryzae laccase was studied and Congo Red exhibited maximum decolorization percentage (64 ± 1.3%) at 15 µM, 50 °C and pH 4.5. The kinetic study of different dye (Congo Red) concentrations obtained Vmax and Km values of 0.123 × 10-3 M and 0.724 mol L-1 min-1, respectively.