Extracellular expression of alkali tolerant xylanase from Bacillus subtilis Lucky9 in E. coli and application for xylooligosaccharides production from agro-industrial waste

An alkali tolerant xylanase gene from Bacillus subtilis Lucky9 was cloned and extracellular expressed in E. coli BL21. Xylanase amino acid sequence showed 99% identity with xylanase sequence from Bacillus subtilis 168, and was belonged to glycoside hydrolase family 11. The recombinant E. coli (pET-pelB-xynLC9) containing pelB signal peptide produced extracellular xylanase of 436.5 U/mL for 8 h, which was used arabinose as extra carbon source and inducer for enhancing extracellular production. The extracellular xylanase was determined by SDS–PAGE with a relative molecular mass of 21 kDa. The recombinant xylanase was optimally activity at pH 6.5 and 60 °C. The xylanase exhibited 80% residual activity over a broad pH range of 6.0–9.0 for 24 h. Thermostability studies showed that xylanase retained 60% residual activity after 2 h at 60 °C. The main end-products of hydrolysis of beech-wood xylan and corncob by the extracellular xylanase were xylobiose and xylotriose. This extracellular xylanase without purification is a suitable candidate for application in the industrial production of xylooligosaccharides from agro-industrial waste for use as prebiotics.