[Regulation of key enzymes in tryptophan biosynthesis pathway in Escherichia coli]

To improve tryptophan production in Escherichia coli, key genes in the tryptophan biosynthesis pathway -aroG, trpED, trpR and tnaA were manipulated. TrpR gene was knocked out to eliminate the repression on the key genes controlling tryptophan biosynthesis and transportation on bacteria chromosome, and the tryptophan degradation was blocked by tnaA gene knockout. Then the bottleneck in tryptophan biosynthesis pathway was removed by co-expressing aroGfbr gene and trpEDfbr gene. Compared with the MG1655, the tryptophan production of trpR knockout and double-genes knockout strains was improved 10-folds and about 20-folds, respectively. After the trpEDfbr was expressed, the tryptophan production increased to 168 mg/L, and when the aroGfbr and trpEDfbr were co-expressed, the tryptophan production increased to 820 mg/L. This work laid the foundation for further construction of higher-efficient engineered strain for tryptophan production.