The Studies Of Fermentation Control For2-KGA Production Based On SDH Enzymatic Reaction

2-keto-L-gulonic acid(2-KGA), which is a precursor of Vitamin C, is mainly produced through two-step fermentation. The mixed fermentation at the second step is the key process. In this paper, the relation between B.cereus and K.vulgare, and environmental factors were studied based on the enzymatic reaction in2-KGA fermentation process with Bacterial System25b.The results indicate that:the cell density of B.cereus in fermentation is increased significantly, when the density of B.cereus in the inoculum is increased to0.4～0.5(OD650). And the cell density of K.vulgare is also increased significantly with the increasing inoculum cell density of K.vulgare, especially when the OD650is over0.15, the conversions is raised to80%.The fermentation process can be divided into three periods, that is Period G1(0～20h), Period G2(20-30h), Period P(30h to end), based on cell growth and2-KGA synthesizing. According to that, the environment factors, such as pH, temperature, ventilation and metal ions, were also studied in the paper. The results showed that:(1)The cell growth rate of B.cereus and K.vulgare, yield of2-KGA were improved by5.29%,21.02%and6%with the piecewise pH control strategy (G1pH7.0â†'G2pH6.0â†'pH7.0);(2)With the piecewise temperature control strategy (G132℃â†'G229℃â†'P32℃), the cell growth rate of B.cereus and K.vulgare, yield of2-KGA were improved by6.9%,21.4%and5.2%;(3)With the piecewise ventilation control strategy (G170mLâ†'G2l20mLâ†'P120mL), the cell growth rate of cereus and K.vulgare, yield of2-KGA were improved by25.9%,57.1%and12.4%;(4)A lower Mg2+concentration (0.03～0.05%) can promote the growth of B.cereus and K.vulgare, and a higher Mg2+concentration (0.07%) was beneficial to the synthesis of2-KGA, but inhibited the growth of bacteria;(5)With a MnCl2mass fraction of0.3%, the growth of bacteria and synthesis of2-KGA were improved significantly. These results can be a theoretical basis for studying the mechanism of mixed fermentation and fermentation optimization.