Characterisation of a thermostable xylanase from Chaetomium sp. and its application in Chinese steamed bread

A novel thermophilic xylanase-producing fungus, Chaetomium sp. CQ31 produced 131 U ml−1 of xylanase when grown on a medium containing corncob (3.5%, w/v) at 37 °C for 6 days. A low molecular xylanase was purified 6.5-fold to homogeneity with a recovery yield of 17.5%. Its molecular mass was estimated to be 25.1 kDa by SDS–PAGE. The xylanase had an optimum pH of 7.5, and its optimal temperature was 65 °C. Apparent Km values of the xylanase for birchwood, beechwood and oat-spelt xylan were 1.3, 0.86 and 4.4 mg/ml, respectively. The influence of this xylanase on the quality of Chinese steamed bread (CSB) was further studied. Addition of xylanase in the range 2.5–5.0 ppm caused a 20–24.5% increase in specific volume over the control and remarkable decrease (8.9–24.2%) in firmness was also noticed. This is the first report on the purification, characterisation and application of a xylanase from Chaetomium sp. CQ31.