Study On Producing L-Tryptophan By Escherichia Coli Fermentation

The production of L-tryptophan by microbial fermentation using Escherichia coli KC-102as strain has been studied in this dissertation. The main research contents and results are as follows:1. The physiological characteristics and biochemical traits and fermentation of amino acid capacity of the stain Escherichia coli KC-102were researched and analyzed preliminarily. L-tryptophan concentration in fermented broth was quantitatively determined with method of p-dimethylaminobenzaldehyde colorimetry. Establish a rapid determination method for L-tryptophan contents in the fermented broth. The effect of culture conditions of L-tryptophan accumulation was determined. The production of L-tryptophan of the strain KC-102was up to1.45g/L after fermentation for40hours.2. In this dissertation the batch fermentation conditions with strain KC-102in shake-flask were studied. The optimum seed culture conditions were obtained by single-factor experiment. The optimum composition of fermentation medium was obtained by response surface methodology (RSM). Under the optimum culture conditions, strain KC-102could produce L-tryptophan2.64g/L after flask-shaking fermentation for40hours.3. The fed-batch fermentation of L-tryptophan in5-liter and15-liter fermentor was investigated. The optimum initial glucose concentration and glucose concentration in fermentation process were determined. Based on the fed-batch fermentation in5-liter fermentor, fed-batch fermentation in15-liter fermentor was performed. Under the optimum culture conditions, because of the technology of low glucose, production of L-tryptophan was up to11.21g/L after fermentation for40hours. The production of L-tryptophan reached12.44g/L by adding L-glutamine.