title: Knocking out analysis of tryptophan permeases in Escherichia coli for improving L-tryptophan production.
abstract: Three permeases, Mtr, TnaB, and AroP, are involved in the uptake of L-tryptophan in Escherichia coli. These permeases possess individual function for cell transportation and metabolism, and affect extracellular L-tryptophan accumulation. In this study, by knocking out three tryptophan permeases separately and simultaneously in L-tryptophan-producing strain E. coli GPT1002, we analyzed the effect of permease knock out on L-tryptophan uptake, cell growth, and L-tryptophan production. We found that TnaB is the main transporter that is responsible for the uptake of L-tryptophan. Inactivation of tnaB improved the L-tryptophan production significantly, and inactivation of aroP has an additive effect on tnaB mutant. Quantitative real-time PCR analysis confirmed that knocking out permeases affects gene transcription and cell metabolism in many metabolic pathways. The tryptophan permease-deficient GPT1017 mutant exhibited the highest L-tryptophan production at 2.79 g l(-1), which is 51.6 % higher than that produced by the control strain. In 5-l bioreactor fermentation, the L-tryptophan production in GPT1017 reached 16.3 g l(-1).
authors.affiliation: State Key Laboratory of Microbial Technology, 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: Fangfang
authors.initials: F
authors.lastname: Li
authors.forename: Quanfeng
authors.initials: Q
authors.lastname: Liang
authors.forename: Qingsheng
authors.initials: Q
authors.lastname: Qi
mesh_terms: D026905:Amino Acid Transport Systems / Q000235:genetics*; D001483:Base Sequence; D017931:DNA Primers; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D029968:Escherichia coli Proteins / Q000235:genetics*; D017353:Gene Deletion; D055785:Gene Knockdown Techniques; D060888:Real-Time Polymerase Chain Reaction; D014158:Transcription, Genetic; D014364:Tryptophan / Q000096:biosynthesis*
chemical_list: D026905:Amino Acid Transport Systems; D017931:DNA Primers; D029968:Escherichia coli Proteins; C069255:mtr protein, E coli; D014364:Tryptophan