Expression of the Thermotolerant Xylanase Gene xyn11EM in Escherichia coli

Abstract:

A codon-optimized gene（named xyn11EM），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/xyn11EM），expressing the thermostable xylanase，was constructed by transforming the recombinant plasmid，pET-28a-xyn11EM，into E. coli BL21（DE3）. The recombinant E. coli BL21/xyn11EM was induced with IPTG to express reXyn11EM. The reXyn11EM activity reached 47.5 U/mL. The apparent molecular weight of reXyn11EM 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 Vmax of reXyn11EM toward birchwood xylan were 7.2 mg/mL and 54.7 U/mg. The excellent thermostability of reXyn11EM make it has great potential in industrial application.