One-step of tryptophan attenuator inactivation and promoter swapping to improve the production of L-tryptophan in <it>Escherichia coli</it>

• Main Authors: Gu Pengfei, Yang Fan, Kang Junhua, Wang Qian, Qi Qingsheng
• Format: Article
• Language: English
• Published: BMC 2012-03-01
• Series: Microbial Cell Factories
• Online Access: http://www.microbialcellfactories.com/content/11/1/30

<p>Abstract</p> <p>Background</p> <p>L-tryptophan is an aromatic amino acid widely used in the food, chemical and pharmaceutical industries. In <it>Escherichia coli</it>, L-tryptophan is synthesized from phosphoenolpyruvate and erythrose 4-phosphate by enzymes in the shikimate pathway and L-tryptophan branch pathway, while L-serine and phosphoribosylpyrophosphate are also involved in L-tryptophan synthesis. In order to construct a microbial strain for efficient L-tryptophan production from glucose, we developed a one step tryptophan attenuator inactivation and promoter swapping strategy for metabolic flux optimization after a base strain was obtained by overexpressing the <it>tktA</it>, mutated <it>trpE </it>and <it>aroG </it>genes and inactivating a series of competitive steps.</p> <p>Results</p> <p>The engineered <it>E. coli </it>GPT1002 with tryptophan attenuator inactivation and tryptophan operon promoter substitution exhibited 1.67 ~ 9.29 times higher transcription of tryptophan operon genes than the control GPT1001. In addition, this strain accumulated 1.70 g l^-1L-tryptophan after 36 h batch cultivation in 300-mL shake flask. Bioreactor fermentation experiments showed that GPT1002 could produce 10.15 g l^-1L-tryptophan in 48 h.</p> <p>Conclusions</p> <p>The one step inactivating and promoter swapping is an efficient method for metabolic engineering. This method can also be applied in other bacteria.</p>