Overexpression of GH10 endoxylanase XynB from Thermotoga maritima in Escherichia coli by a novel vector with potential for industrial application

The GH10 endoxylanase B encoded by xynB of Thermotoga maritima is a particularly attractive candidate for some industrial purposes. In present study, we aimed to develop an expression system to increase the enzyme production and decrease the costs in the induction of xynB expression in Escherichia coli. The xylanase was overexpressed in E. coli by using the novel pHsh expression vector. After optimization of the mRNA secondary structure in translational initiation region of pHsh-xynIII, the Gibbs free energy of 73 nt was changed from −10.5 kcal mol−1 to −6.71 kcal mol−1, and the SD sequence was completely released to a large loop. The nucleotide sequence changes resulted in the increase of expression level of xynB from 276 U ml−1 to 489 U ml−1 in LB medium, and from 977 U ml−1 to 1893 U ml−1 in Terrific broth. Moreover, the recombinant XynB was successfully expressed in fermentors by using “flow-in-heat” method. Thus, this report provides an industrial means to produce the extremely thermostable xylanase in E. coli.