Effects of oxygen carrier on the biosynthesis of welan gum by Sphingomonas sp. ATCC 31555

In welan gum fermentation process by Sphingomonas sp. ATCC 31555, the level of dissolved oxygen drops with the viscosity of broth increasing, leading to the reduced yield of welan gum. To improve the oxygen concentration in the fermentation system and increase welan gum yield the addition of oxygen carrier was studied and multiple adding methods were used. Glycerin had no significance on welan gum yield, while dodecane, n-hexane, H2O2 could increase the yield of welan gum to a certain degree, and H2O2 was the best oxygen carrier. Optimizing adding concentration and time of H2O2 with one-factor experimental design were 15 mmol/L at the 8 h in fermentation, and Glucose utilization increased at the same time. In addition, 1.91% of welan gum was obtained when adding 5 mmol/L H2O2 at the 4, 8, 12 h keeping the total amount (15 mmol/L) of adding H2O2 constant, increased 30.02% comparing with the blank group. Moreover, a small amount of complete cells could be observed in the experimental group at 72 h fermentation, when extended the fermentation period to the 84 h, 1.99% of welan gum was obtained, increased 4.21% comparing with the group of 72 h in fermentation. 5 L fermentation of expand training had welan yield 2.09%, higher than shake flask experiment results. ©, 2015, Editorial Department of Journal of Sichuan University. All right reserved.