中文摘要：

将人工合成经密码子优化的11家族耐热木聚糖酶基因xyn11^EM克隆至表达质粒pET-28a（＋）中，获得重组质粒pET-28a-xyn11^EM。将其转化Escherichia coli BL21（DE3），构建表达耐热木聚糖酶的重组工程菌E. coli BL21/xyn11^EM。用IPTG诱导表达重组木聚糖酶Xyn11^EM（reXyn11^EM），酶活性可达47.5 U/mL。SDS-PAGE分析显示，reXyn11^EM的表观相对分子质量为24 800。reXyn11EM的最适反应温度为70 ℃，在70 ℃以下稳定。最适反应pH为6.5-7.0，在pH 5.0-8.0范围内稳定。大多数金属离子和EDTA对该重组酶的活性影响不大。reXyn11^EM的Km和Vmax值分别为7.2 mg/mL和54.7 U/mg。结果表明xyn11^EM成功在E. coli 中实现了异源表达，其良好的热稳定性具有较好的工业应用潜力。

英文摘要：

A codon-optimized gene （named xyn11^EM）, which encodes a thermotolerant xylanase belonging to the glycoside hydrolase family 11, was synthesized, and cloned into the expression plasmid pET-28a （＋）. The recombinant Escherichia coli （designated E. coli BL21/xyn11^EM）, expressing the thermostable xylanase,was constructed by transforming the recombinant plasmid, pET-28a-xyn11^EM,into E. coli BL21 （DE3）. The recombinant E. coli BL21/xyn11^EM was induced with IPTG to express reXyn11^EM. The reXyn11^EM activity reached 47.5 U/mL. The apparent molecular weight of reXyn11^EM was estimated to be 24 800 by SDS-PAGE analysis. Its optimal temperature and pH were 70 ℃ and 7.0,respectively. It was stable at a temperature of 70℃ or below, and at a pH range of 5.0-8.0. Its activity was not significantly affected by most of metal ions tested and EDTA. The Km and of reXyn11^EM toward birchwood xylan were 7.2 mg/mL and 54.7U/mg. The excellent thermostability of reXyn11^EM make it has great potential in industrial application.