Effects of carbon/nitrogen ratio, dissolved oxygen and impeller type on gellan gum production in Sphingomonas paucimobilis

Abstract

Among exopolysaccharides, gellan gum is used widely as a gelling agent and food additive, and its commercial market is rapidly increasing. To optimize the fermentation production of gellan gum in Sphingomonas paucimobilis ZJU3108, carbon/nitrogen (C/N) ratio, dissolved oxygen (DO) and impeller type were studied. The C/N ratio, rather than the absolute concentration of carbon or nitrogen source, was found to be the major factor affecting cell growth. A C/N ratio above 20.7 had no significant effect on gellan gum production. Although the final yield of gellan gum increased with C/N ratio increase, the glucose to gellan gum conversion rate decreased. This was due to the high viscosity, which caused oxygen limitation from 16 h to 40 h in the inhomogeneous broth. Due to low stationary phase oxygen demand, the effect of DO on biomass and gellan gum production was reduced. A simple DO control strategy was developed to maintain 30% DO for the first 32 h cultivation, followed by anaerobic conditions for the remaining 8 h. Comparison of different impellers suggested that an anchor impeller with impeller diameter of 11.0 cm (D*=11.0 cm) was suitable for high yields of high molecular weight gellan gum. These studies simplify production of gellan gum by fermentation and improve its yield.

Optimization of cultural conditions of gellan gum production from recombinant Sphingomonas paucimobilis ATCC 31461 and its characterization

“…According to Huang et al [34], dissolved oxygen plays a key role in many aspects of cellular metabolism in aerobic organisms like S paucimobilis. The influence of dissolved oxygen on biomass and gellan production is depicted in Figure 3c and d.…”