Novel catalytic and effluent decolorization functionalities of sol-gel immobilized Pleurotus ostreatus IBL-02 manganese peroxidase produced from bio-processing of wheat straw

Abstract

Solid state bio-processing of wheat straw was carried out through an indigenous fungal strain Pleurotus ostreatus IBL-02 under pre-optimized fermentation conditions. The maximum activity, 692±12 U/mL, of the industrially important manganese peroxidase (MnP) enzyme was recorded after five days of still culture incubation. The crude MnP was 2.1-fold purified with a specific activity of 860 U/mg after purification on a Sephadex-G-100 gel column. On native and SDS-PAGE electrophoresis gels, the purified MnP fraction was a single homogenous band of 45 kDa. An active fraction of MnP was immobilized using hydrophobic sol-gel entrapment comprising tetramethoxysilane (T) and propyltrimethoxysilane (P) at different T:P molar ratios. Characterization revealed that after 24 h incubation at varying pH and temperatures, the MnP fraction immobilized at a T:P ratio of 1:2 in the sol-gel retained 82% and 75% of its original activity at pH 4 and 70°C, respectively. The optimally active fraction at a 1:2 T:P ratio was tested against MnSO 4 as a substrate to determine the kinetic catalytic constants K M and V max . To explore the industrial applicability of P. ostreatus IBL-02 MnP, both the free and immobilized MnP were used for the decolorization of four different textile industrial effluents. A maximum of 100% decolorization was achieved for the different textile effluents within the shortest time period. A lower K M , higher V max , hyper-activation, and enhanced acidic and thermal resistance up to 70 °C were the novel catalytic features of the sol-gel immobilized MnP, suggesting that it may be a potential candidate for biotechnological applications particularly for textile bioremediation purposes. Agro-industrial based lignocellulosic waste material i.e. wheat straw was used as a fermentation feed stuff for MnP production. A promising and eco-friendly approach was adopted to immobilize the purified MnP into the sol-gel matrix network. To explore the textile industrial applicability, the immobilized MnP was tested against real dye containing textile effluents.