Purification and characterization of a thermostable xylanase from Paenibacillus sp. NF1 and its application in xylooligosaccharides production.

High levels of extracellular xylanase activity (211.79 IU/mg) produced by Paenibacillus sp. NF1 were detected when it was submerged-cultured. After three consecutive purification steps using Octyl-Sepharose, Sephadex G75, and Q-Sepharose columns, a thermostable xylanase (XynNF) was purified to homogeneity and showed a molecular mass of 37 kDa according to SDS-PAGE. The specific activity of the purified XynNF was up to 3,081.05 IU/mg with a 14.55-fold purification. The activity of XynNF was stimulated by Ca(2+), Ba(2+), DTT, and β-mercaptoethanol, but was inhibited by Fe(3+), Zn(2+), Fe(2+), Cu(2+), SDS, and EDTA. The purified XynNF displayed a greater affinity for oat spelt xylan with the maximal enzymatic activity at 60°C and pH 6.0. XynNF, which was shown to be cellulose-free, with high stability at high temperature (70°C-80°C) and low pH range (pH 4.0-7.0), is potentially valuable for various industrial applications. The end products of high efficient oat spelt xylan hydrolysis by XynNF (an endoxylanase) containing 95.8% xylooligosaccharides of 2-4 degree of polymerization (DP2-4) with the enrichment of xylobiose (61.5%) indicated that XynNF is a promising candidate for xylooligosaccharides production.