food chemistry.pdf

Food Chemistry 120 (2010) 457–462Contents lists available at ScienceDirect Food Chemistry journal homepage: www.elsevier .com/locate / foodchemCharacterisation of a thermostable xylanase from Chaetomium sp. and its application in Chinese steamed bread Zhengqiang Jiang a,*, Qianqian Cong a, Qiaojuan Yan b, Narasimha Kumar a, Xuedan Du b aDepartment of Biotechnology, College of Food Science and Nutritional Engineering, China Agricultural University, Beijing 100083, China bBioresource Utilization Laboratory, College of Engineering, China Agricultural University, Beijing 100083, China a r t i c l e i n f oArticle history: Received 18 July 2009 Received in revised form 1 September 2009 Accepted 13 October 2009 Keywords: Characterisation Chaetomium Chinese steamed bread Purification Thermostable Xylanase0308-8146/$ - see front matter  2009 Elsevier Ltd. A doi:10.1016/j.foodchem.2009.10.038 Abbreviations: BSA, bovine serum albumin; CAP panesulphonic acid; CHES, 2-(cyclohexylamino)etha boxymethylcellulose; CSB, Chinese steamed bread; DN ethylenediaminetetracetic acid; PDA, potato dextros difluoride; TLC, Thin-layer chromatography. * Corresponding author. Address: Department of Bi Science and Nutritional Engineering, China Agricultura 17 Qinghua Donglu, Haidian District, Beijing 100083, C fax: +86 10 E-mail address: zhqjiang@ (Z. Jiang).a b s t r a c t A novel thermophilic xylanase-producing fungus, Chaetomium sp. CQ31 produced 131 U ml1 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 st