Space Screening Of New Strains And Optimization Of Conditions For Two-stage Fermentation Of Vitamin C

In the process of Vitamin c production by method of two-step fermentation, the second step which converts L-sorbose to2-Keto-L-gulonic is a mixed culture, it contains two bacteria, the converter bacterium(Gluconobacter oxydans)and the helper bacterium (Bacillus megaterium, Bacillus thuringins,etc). Currently, Vitanmin c is extremely competitive in the international market. In order to improve fermentation conversion rate and reduce production costs, it is one of important ways to screening highly efficient strains for Vitamin c producing enterprise.In this paper, the new strains which mutated by space-flight with shenzhou7spacecraft were screened and the fermentation conditions were optimized. The results of experiments as follows:Spaceship carrying selection process, converter and combination of bacteria is picked out respectively from single colony1010and3000. Through the initial screening, secondary screening and screening shaking, ultimately acquire three efficient helper-bacteria320#、433#、988#, and three efficient acid bacteria2264#、2194#、444#. Efficient two-step fermentation strains with acid study with each other to obtain the best combination of a group of BG320-2194. treating average conversion rate than check against to increase5.97%.Examine the new combination of bacteria320-2194characteristics of growth and fermentation.The combination of bacteria in the seed stage, in18hours the number of small bacteria and capacity of product acid reached the best condition.After the fermentation stage, the new combination of gulonic acid accumulation rate of bacteria in the fermentation at0-36hours is always higher than the original strain, there are four hours ahead before the maximum conversion rate of the highest value, turn out that the production of new strains has significant ability to promote gulonic acid accumulation than check, the combination of strains for5approved by the shake flask, the average conversion rate stable reach92.4%. New strains on the fermentation conditions were investigated. The results shows that optimum proportions of peptone is0.2%,the optimum initial concentration of L-sorbose is8%, the optimum volume is15-20ml in250mL flask, the optimum temperature is maintained at29～33℃. the optimized fermentation than the production of bacterium3-6%。...