Isolation, Purification and Characterization of Xylanase produced by Bacillus sp. NIORKP76 strain under solid state fermentation and its application in saccharification of various agro-residues into fermentable sugars

Abstract

Abstract Microbial xylanases are xylan hydrolyzing enzymes which has congregated attention due to their immense potential in many industries. Increasing demand for these enzymes versus inadequate supply makes these biomolecules a value-added product. The current study is focused on xylanase from bacterial isolate identified as Bacillus sp. NIORKP76. The bacterial isolate used in this study showed ability to produce xylanase on an inexpensive agro-industrial waste (wheat bran) under solid-state fermentation. The isolate showed maximum xylanase production in growth media supplemented with phosphate, NaCl and NH4Cl concentration of 64 mM, 15 mg/mL and 0.3 mg/mL respectively. The maximum xylanase titer volume was obtained with 1:3 substrate to moisture ratio (w/v). Using optimized conditions maximum xylanase production in wheat bran was achieved in 72 h at room temperature 28 ±2°C. Xylanase exhibited pH optima of 8.0 and retained 92% of its residual activity after 24h incubation period at pH 8.0, thus proving its high stability at alkaline pH. Xylanase displayed optimum activity at 60°C. Xylanase stability at 30°C and 40 °C remained unhindered even after 12h of incubation period. The xylanase isolated in this study was purified up to homogeneity and its molecular weight was found to be ~28kDa. Xylanase produced by Bacillus sp. NIORKP76 strain was found to have essential qualities required for saccharification of various agro-residues to generate fermentable sugars which can be a raw-material for biofuel production. Wheat bran with heat pre-treatment was found to be par excellence agro-waste as compared to other heat pre-treated and untreated lignocellulosic agro-wastes in production of fermentable reducing sugars. 141mg/g fermentable sugars were whipped up when reaction mixture of pre-treated wheat bran with 5U/g partially purified xylanase incubated at 40°C for 8h, which was found to be best results among all agro-residues studied.