Xylanase of Bacillus sp. NIORKP76 grown under solid state fermentation: production, purification, characterization...

Microbial xylanases are xylan hydrolyzing enzymes which has congregated attention due to their immense potential in many industries. The current study is focused on xylanase from bacterial isolate identified as Bacillus sp. NIORKP76 on an inexpensive agro-industrial waste (wheat bran) under solid-state fermentation. The isolate showed maximum xylanase production in growth medium supplemented with phosphate, NaCl and NH₄Cl at 64 mM, 15 mg/mL and 0.3 mg/mL respectively which was maintained at 1:3 substrate to moisture ratio (w/v). Using optimized conditions, the maximum xylanase production in wheat bran was achieved in 72 h at room temperature 28 ± 2 °C. Xylanase exhibited pH optimum of 8.0 and retained 92% of its residual activity after 24 h incubation at pH 8. Xylanase displayed optimum activity at 60 °C, whereas it remained unhindered even after 12 h of incubation period at 30 and 40 °C. The xylanase isolated in this study was purified to homogeneity with a molecular weight of approximately 28 kDa. Xylanase from Bacillus sp. NIORKP76 was potentially converting agro-residues into biofuel feedstock. Pretreated wheat bran produced the highest yield fermentable sugars (141 mg/g), after 8 h incubation with 5 U/g xylanase and at 40 °C.