Effect of gene knockouts of l-tryptophan uptake system on the production of l-tryptophan in Escherichia coli
2012
Zhao, Zhijun | Chen, Sheng | Wu, Dan | Wu, Jing | Chen, Jian
Uptake of l-tryptophan in Escherichia coli was carried out by three distinct permeases, Mtr, TnaB, and AroP, respectively. In the present study, the three genes of l-tryptophan uptake system were knocked out from an l-tryptophan-producing strain of E. coli, respectively. The knockout mutants all showed lower l-tryptophan uptake activities and higher l-tryptophan production than their parent. Among the three genes, the knockout of mtr was most critical for both l-tryptophan uptake and l-tryptophan production. The uptake activity of l-tryptophan of the mtr mutant was 1.5nmolmin⁻¹ (mg dry weight)⁻¹, which was decreased by 48% when compared to that of the parent; the production of l-tryptophan of the mtr mutant was 14.7g/l, which was increased by 34% when compared to that of the parent. Furthermore, the physiological and fermentation characteristics caused by gene knockouts were also analyzed.
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