Hyperproduction and characterization of a cost-effective manganese peroxidase from Pleurotus ostreatus using response surface methodology under solid state fermentation

Manganese peroxidase (MnP) is a lignin-degrading enzyme required in the ligninolytic process catalyzing oxidation of Mn²⁺ to Mn³⁺. It has the ability to degrade nitroaromatic compounds, chlorophenols, and polycyclic aromatic hydrocarbons, all of which contribute to organic pollution. In this work, an indigenous strain of white-rot fungus Pleurotus ostreatus (oyster mushroom) was employed for hyperproduction of MnP using response surface methodology (RSM) under solid state fermentation through screening of local biomass. Among the parameters, 14 days incubation period, pH 4, 30 °C temperature, 8.0 g substrate concentration, 4.5 mL inoculum size, 60% moisture content, 2.87 g nitrogen supplement, and 0.082 g magnesium sulphate were found as the optimized conditions for production of manganese peroxide. Peanut shell was found as the best substrate for maximum production of enzyme (74.70 U/mL). The degradation of guaiacol as a substrate by MnP was also confirmed through Fourier Transform Infrared spectroscopy, which showed the absence of a peak of -C=O at 1636.6 cm-1 and –OH at 3331.4 cm-1 as structural components of guaiacol, after degradation by MnP. Peanut shell is easily available as agriculture residue. Therefore, hyper-produced MnP from P. ostreatus could lead to cost effective exploitation of further enzymes for industrial applications.