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

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