Hyper-production of manganese peroxidase by mutant Pleurotus ostreatus MTCC 142 and its applications in biodegradation of textile azo dyes

Abstract

Enhanced production of manganese peroxidase (MnP) by the mutant Pleurotus ostreatus MTCC 142 was carried out in a solid and submerged fermentation by using an agro-industrial waste (rice bran and wheat bran) under optimized conditions. Among the various substrate combinations examined, rice bran shows the highest MnP activity (273 U/L), when compared with the wheat bran (218 U/L). Maximum MnP (368 U/L) was produced when rice bran (5 g) at 75% moisture (w/v) was used with 1 mL inoculum at pH 4 and 25°C in the presence of 2% (w/v) glucose as a carbon source, 0.2% (w/v) sodium nitrate as a nitrogen source and 4% of (v/v) glycerol as an inducer for MnP production under submerged fermentation. MnP was purified from the culture fluid by using microfiltration (1.2 μm) and ammonium sulphate precipitation followed by ion exchange chromatography. Additionally, the protein content of the recovered supernatant was also noted. The purified MnP was a monomer, which showed a molecular mass of 58 ± kDa as determined by SDS-PAGE. Furthermore, the purified MnP was exploited for decolourization of structurally different azo dyes. Among the selected azo dyes, Ponceau S, Tartrazine and Trypan Blue were decolourized rapidly by the purified enzyme extracts under optimized condition and it was found to be 78, 56 and 59%, respectively.