Study On Optimization Of Riboflavin Fermentation By B. Subtilis X42

B. subtilis X42 is the germ we have researched in this paper. we first verify some factors who may promote the production of riboflavin by using single-factor method ,and then the Plackett-Burman and response surface analysis is implemented to determine the composition of the ultimate medium in shake flask. Finally, we also have researched the fermentation medium and the optimal culture parameters for maximum riboflavin production in 5L fermentor.We find yeast power is the best nitrogen source ,we also have researched the function of additional nitrogen source by using the single-factor method , and find that 0.3%urea can significantly promote the production of riboflavin. In addition,we also use the same method to study the effection of these single factors which are succinic acid,sodium citrate,asparagine, aspartic acid,glutamic acid,glutamine,serine and xanthine, hypoxanthine,guanine on the riboflavin production of B. subtilis X42,and found no significant effect.Plackett-Burman (PB) design is implemented to screen medium components that significantly influence riboflavin production. And find out six significant effect factors among the 11 variables .The six major components are glucose,yeast powder, MgSO₄·7H₂O, urea, CuCl₂, MnCl₂. One of the negative impact factors is MnCl₂ whose bottom level is 0.So MnCl₂ will not be added in the futher experiment. Select yeast powder,urea, CuCl₂ to do the response surface analysis for the purpose of getting the optimal medium of riboflavin production.The production of riboflavin is 7.9 g / L±0.4 g / L by the optimized medium in shake flasks, and increased 11.2% comparing with the control medium.By single-factor method to determine the fermentation temperature and pH , we find that optimum fermentation temperature is 41℃,and the optimum fermentation pH is 6.8. In this paper, By using the glucose-limited fed-batch mode (glucose concentration is maintained at 5 10 g / L),we find that the final yield of riboflavin is 8.5 g / L and biomass is 13.3g / L when 2% yeast powder and 0.3% urea as nitrogen source which are shortage. So we increase yeast powder up to 3% and urea up to 0.6%,and add 0.5% of corn steep powder and 0.5% of yeast extract,finding that the final output of fermentation riboflavin is up to 12.5g / L and biomass up to 22.1g / L .