Purification and characterization of a moderately thermostable xylanase from Bacillus sp. strain SPS-0

A Bacillus spp. strain SPS-0, isolated from a hot spring in Portugal, produced an extracellular xylanase upon growth on wheat bran arabinoxylan. The enzyme was purified to homogeneity by ammonium sulfate precipitation, anion exchange, gel filtration, and affinity chromatography. The optimum temperature and pH for activity was 75°C and 6.0. Xylanase was stable up to 70°C for 4 h at pH 6.0 in the presence of xylane. Xylanase was completely inhibited by the Hg2+ ions. β-Mercaptoethanol, dithiothreitol, and Mn2+ stimulated the xylanase activity. The products of birchwood xylan hydrolysis were xylose, xylobiose, xylotriose, and xylotetraose. Kinetic experiments at 60°C and pH 6.0 gave Vmax and Kmvalues of 2420 nkat/mg and 0.7 mg/ml.