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Microb Cell Fact. 2012 Mar 2;11:30. doi: 10.1186/1475-2859-11-30.

One-step of tryptophan attenuator inactivation and promoter swapping to improve the production of L-tryptophan in Escherichia coli.

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  • 1State Key Laboratory of Microbial Technology, National Glycoengineering Research Center, Shandong University, Jinan 250100, People's Republic of China.



L-tryptophan is an aromatic amino acid widely used in the food, chemical and pharmaceutical industries. In Escherichia coli, 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 tktA, mutated trpE and aroG genes and inactivating a series of competitive steps.


The engineered E. coli 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(-1) L-tryptophan after 36 h batch cultivation in 300-mL shake flask. Bioreactor fermentation experiments showed that GPT1002 could produce 10.15 g l(-1) L-tryptophan in 48 h.


The one step inactivating and promoter swapping is an efficient method for metabolic engineering. This method can also be applied in other bacteria.

© 2012 Gu et al; licensee BioMed Central Ltd.

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