Screening Of Companion Bacteria And Optimization Of Conditions For Two-stage Fermentation Of Vitamin C

In an industrial vitamin C manufacturing procedure, a two-step fermentation is adopted converting D-sorbitol is involved in the frist step fermentation. In the second step, a two-cell line co-fermentation system, which contains Gluconobacter oxydans as the converter and Bacillus megaterium as the helper, L-sorbose is converted to 2-keto-L-gulonic aicd(2-KGA), which is the precursor of Vc.The paper is that the Bacillus thuringiensis from different sources were done separation,purification and insect rejuvenation, then reasearched the genetic stability and selected a new strains B15-14 composed with associated bacteria and the production acid bacteria (Gluconobacter oxydans), moreover, seen about the biological characteristics. The result shows that compared to the manufacture strains 25B, the new mixed strains present that the fermentation periods of shaking flake shorted 4h, the conversion ratio from glycose to acid rose 5.5%, the characteristics kept stability by research of generations incubation.The characteristics of Growth and fermentation of the mixed strains of Vc B15-14 is that seed culture medium of new mixed strains has a remarkble trait is that the exponential phase stands long and the quantitive ratios of big-small bacteria are lower than the ck in the same periods, what is more, the growth rate of B15-14 is faster than ck and the increasement of bacterial biomass is quick.To better carry on the fermentation potential of new strains B15-14, the single factor fermentation condition was studied. The results shows that the optimum inoculum age is 22~24h, the optimum inoculation is10-15%, the optimum volume is 20 ml in 250ml flask, the the optimum initial concentration of L-sorbose is 8%, the optimum temperature of fermentation is 29℃~31℃, and the optimum initial pH is 6.7~7.0.The condition of the fermentation culture medium of new strains B15-14 was optimized by uniform design method. The conclusion is that in our choice bound the componential concentration of the optimized culture medium is that Corn Syrup is 3.02%,KH2PO4 is 0.25%,MgSO4 is 0.03%,Urea is 0.43%. Under the optimized condition, the average conversion rate of ten batches experiments of the B15-14 in shaking flakes was increased by 3.32%, and the fermentation period reduced by 2.2h against the control, the B15-14 showed higher application value.