Mutation Screening Of High-producers Of L-tryptophan And Optimizing Of Fermentation Process

In order to increase the amount of L-tryptophan produced by the metabolic fermentation of microbial strains,this paper focused on the selection of L-tryptophan strains and optimization of fermentation process.In order to reduce the production cost,the yield of L-tryptophan can be greatly increased.Based on the above objectives,the main findings of this paper are as follows:(1)Using Escherichia coli as the starting strain,by UV and diethyl sulfate(DES)mutagenesis treatment,it was found that when the ultraviolet irradiation time was 20 s and the DES mutagenesis time was 40 min,the lethality rate was about 80%d,and In the DES mutagenesis process,the optimal mutagenic concentration of diethyl sulfate was determined by experimental design to be 1%,and then the high-yield strain was screened by passage.The highest yield of L-tryptophan was produced by trampoline fermentation to 4.36 g./L.(2)The optimal seed culture medium of the strain was obtained by optimizing the experimental design of the culture medium.When the temperature was 34 ° C and the p H value was 6.9.In addition,it was found that when the inoculation amount was 12% and the inoculation age was 18 h,the growth rate of the bacteria was the fastest,and the acid yield of L-tryptophan reached the maximum value of 50.5g/L.(3)The fermentation tanks is optimized by batch fermentation process,the rotation speed is 400-800r/min,the culture temperature is 34°C,the p H is controlled at 6.9,and the glucose is controlled in the critical state between 2g/L-5g/L.The specific growth rate is the fastest,the inorganic salt is 0.79 times based on the concentration of zinc sulfate heptahydrate,and the concentration of manganese sulfate monohydrate is 1.13 times.When the dissolved oxygen concentration is controlled at 20%-30%,the cells are in optimal growth state.At this time,the yield of L-tryptophan was the highest,reaching 55.1 g/L.By optimizing the L-tryptophan production strain and optimizing the fermentation process,the yield of L-tryptophan is greatly improved.