title: One-step of tryptophan attenuator inactivation and promoter swapping to improve the production of L-tryptophan in Escherichia coli.
abstract: 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.
authors.affiliation: State Key Laboratory of Microbial Technology, National Glycoengineering Research Center, Shandong University, Jinan 250100, People's Republic of China.
authors.forename: Pengfei
authors.initials: P
authors.lastname: Gu
authors.forename: Fan
authors.initials: F
authors.lastname: Yang
authors.forename: Junhua
authors.initials: J
authors.lastname: Kang
authors.forename: Qian
authors.initials: Q
authors.lastname: Wang
authors.forename: Qingsheng
authors.initials: Q
authors.lastname: Qi
mesh_terms: D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D005285:Fermentation; D005947:Glucose / Q000378:metabolism; D060847:Metabolic Engineering; D009876:Operon; D011401:Promoter Regions, Genetic; D014158:Transcription, Genetic; D014364:Tryptophan / Q000096:biosynthesis*
chemical_list: D029968:Escherichia coli Proteins; D014364:Tryptophan; D005947:Glucose