不依赖IPTG诱导产木糖醇大肠杆菌工程菌的构建

该研究采用分子生物学技术构建不依赖异丙基-β-D-硫代半乳糖苷（IPTG）诱导产木糖醇的大肠杆菌（Escherichia coli）工程菌，并研究启动子、质粒拷贝数、诱导剂IPTG的添加、基因xylA和xylB的敲除以及木糖含量对工程菌发酵产木糖醇的影响。结果表明，当转速为200 r/min时，E. coli AI07/pWYZ-1（启动子为lacP）的木糖醇产量是E. coli AI07/pAGI02（启动子为pflB-p6）的1.8倍；E. coli AI07/pWYZ-2（中拷贝质粒pBR322）的木糖醇产量高于E. coli AI07/pWYZ-1（高拷贝质粒pUC19），分别为19.56 g/L、7.90 g/L；是否添加诱导剂IPTG对E. coli AI07/pWYZ-2产木糖醇影响不大，且在发酵96 h时，木糖醇产量极显著高于E. coli AI05/pWYZ-2（P＜0.01），其在不添加IPTG的条件下，当木糖初始质量浓度为80 g/L，发酵时间为108 h时，木糖醇产量达48.7 g/L。

Construction of IPTG-inducing independent engineered Escherichia coli for xylitol production

The engineered Escherichia coli that does not rely on isopropyl-β-D-thiogalactoside (IPTG) to induce xylitol production was constructed by molecular biological technique, and the effects of promoter, plasmid copy number, inducer IPTG addition, genes xylA and xylB knockout, and xylose concentration on the production of xylitol by engineered bacteria were investigated. The results showed that when the rotation speed was 200 r/min, the xylitol production of E. coli AI07/pWYZ-1 (lacP as promoter) was 1.8 times that of E. coli AI07/pAGI02 (pflB-p6 as promoter), the xylitol production of E. coli AI07/pWYZ-2 (medium copy plasmid pBR322) was higher than that of E. coli AI07/pWYZ-1 (high copy plasmid pUC19), which was 19.56 g/L and 7.90 g/L, respectively. The addition of inducer IPTG had no significant difference in the production of xylitol by E. coli AI07/pWYZ-2, and the xylitol production after fermentation 96 h was highly significantly higher than that of E. coli AI05/pWYZ-2 (P＜0.01). Without IPTG addition, when the initial xylose concentration was 80 g/L and the fermentation time was 108 h, the production of xylitol by E. coli AI07/pWYZ-2 could reach 48.7 g/L.