Escherichia coli genetically engineered bacterium and application of escherichia coli genetically engineered bacterium to synchronous production of L-tryptophan and L-valine through fermentation

Abstract

The invention provides an escherichia coli genetically engineered bacterium for the synchronous high yield of L-tryptophan and L-valine, and application thereof. The genetically engineered bacterium is obtained through the steps that on a genome of escherichia coli, trpE (S40F) mutation is introduced while a promoter of tryptophan operon is replaced with a Ptrc promoter; an aroG (S180F) gene controlled by the Ptrc promoter is integrated to a tyrR locus; a serA (H344A, N364A) gene controlled by a Plac promoter is integrated to a yjiV pseudo gene locus; a glnA gene controlled by the Plac promoter is integrated to a ycjV pseudo gene locus; and then a bacillus subtilis alsS gene controlled by the Ptrc promoter is integrated to a yghx pseudo gene locus. Shaking flask fermentation is conducted through a strain to be able to accumulate the L-tryptophan within 22-28 h to 10-14 g / L, meanwhile the accumulation amount of valine reaches 5-7 g / L, and the total acid-producing ability is improved by50% or so compared with that of a tryptophan producing strain; and meanwhile, strain OD600 is different slightly, growth problems are avoided, but the acid-producing ability per strain is obviously improved by 120%, and effective utilization of carbon sources and cells is improved greatly.

Description

technical field [0001] The invention relates to an Escherichia coli genetically engineered bacterium and its use for synchronously producing L-tryptophan and L-valine through fermentation, and belongs to the technical field of microbial metabolism regulation and genetic engineering. Background technique [0002] L-tryptophan and L-valine belong to the eight essential amino acids. Because of their nutritional value, they have been widely used in the fields of feed, food and medicine. The production methods of tryptophan and valine include chemical synthesis, enzyme reaction, fermentation, etc., but with the gradual improvement of genetic engineering methods, the use of microbial direct fermentation to produce tryptophan or valine has developed rapidly , the method uses low-priced raw materials such as glucose as a carbon source to produce the target product through microbial fermentation, the production cost is low, and the production process is relatively simple and controll...

AI Technical Summary

Problems solved by technology

At present, most of the research on the metabolic transformation of L-tryptophan production strains is to increase the supply of PEP and E4P, and strengthen the synthesis pathway of L-tryptophan. The metabolic flow of acetic acid is bound to be weakened. At the same time, in the L-tryptophan synthesis pathway, chorismate is enzymatically catalyzed into anthranilic acid, which will be accompanied by a molecule of pyruvate. The supply of oxaloacetate is insufficient, and the TCA cycle is blocked. Unable to metabolize in time and accumulate in large quantities, it is easy to cause the production of various by-products, which ultimately affects cell growth and the accumulation of target products

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