Department of Biotechnology, College of Food Science and Nutritional Engineering, China Agricultural University, Beijing 100083, People's Republic of China.
Appl Biochem Biotechnol. 2011 Jul;164(6):944-56. doi: 10.1007/s12010-011-9186-2. Epub 2011 Feb 8.
A psychrotrophic fungus identified as Trichoderma sp. SC9 produced 36.7 U/ml of xylanase when grown on a medium containing corncob xylan at 20 °C for 6 days. The xylanase was purified 37-fold with a recovery yield of 8.2%. The purified xylanase appeared as a single protein band on SDS-PAGE with a molecular mass of approximately 20.5 kDa. The enzyme had an optimal pH of 6.0, and was stable over pH 3.5-9.0. The optimal temperature of the xylanase was 42.5 °C and it was stable up to 35 °C at pH 6.0 for 30 min. The xylanase was thermolabile with a half-life of 23.9 min at 45 °C. The apparent K(m) values of the xylanase for birchwood, beechwood, and oat-spelt xylans were found to be 3, 2.1, and 16 mg/ml respectively. The xylanase hydrolyzed beechwood xylan and birchwood xylan to yield mainly xylobiose as end products. The enzyme-hydrolysed xylotriose, xylotetraose, and xylopentose to produce xylobiose, but it hardly hydrolysed xylobiose. A xylanase gene (xynA) with an open reading frame of 669 nucleotide base pairs (bp), encoding 222 amino acids, from the strain was cloned and sequenced. The deduced amino acid sequence of XynA showed 85% homology with Xyn2 from a mesophilic strain of Trichoderma viride.
一种嗜冷真菌，鉴定为木霉属 sp. SC9，在 20°C 下生长在含有玉米芯木聚糖的培养基中 6 天，可产生 36.7 U/ml 的木聚糖酶。木聚糖酶经 37 倍纯化，回收率为 8.2%。SDS-PAGE 上的纯化木聚糖酶显示出单一的蛋白质带，分子量约为 20.5 kDa。该酶的最适 pH 为 6.0，在 pH 3.5-9.0 范围内稳定。木聚糖酶的最适温度为 42.5°C，在 pH 6.0 下 35°C 下稳定 30 分钟。木聚糖酶在 45°C 下半衰期为 23.9 分钟，热不稳定。该木聚糖酶对桦木、山毛榉和燕麦-斯佩尔特木聚糖的表观 K(m) 值分别为 3、2.1 和 16mg/ml。木聚糖酶水解桦木木聚糖和山毛榉木聚糖，主要生成木二糖作为终产物。该酶水解木三糖、木四糖和木五糖生成木二糖，但几乎不水解木二糖。从该菌株中克隆和测序了一个木聚糖酶基因（xynA），其开放阅读框为 669 个核苷酸（bp），编码 222 个氨基酸。XynA 的推导氨基酸序列与嗜温菌株绿色木霉的 Xyn2 具有 85%的同源性。
