Efficient Production of Exopolysaccharide by Submerged Fermentation of Hypsizygus marmoreus Using a Two-stage pH Control Strategy.

The effects of culture conditions and pH values on the exopolysaccharides (EPS) production by Hypsizygus marmoreus were investigated in this work. The results showed that the optimal carbon and nitrogen sources were glucose and yeast extract at concentrations of 30 g L-1 and 12.5 g L-1, respectively. In constant pH fermentation, high biomass concentration and the specific cell growth rate were achieved at pH 6.5, while high EPS concentration and the specific EPS production rate were obtained at pH 7.5, respectively. Based on kinetics analysis, a two-stage pH strategy was proposed in which pH was controlled at 6.5 to maintain high cell growth and glucose consumption in the first 48 h, and then shifted to 7.5 for increasing EPS production. The maximal EPS concentration reached 2.31 ± 0.07 g L-1 by applying this strategy. The EPS productivity (0.024 g L-1 h-1) increased 58.94 %, 172.7 % and 35.73 %, respectively, compared with that of the natural pH, and controlling pH at 6.5 and 7.5. [ABSTRACT FROM AUTHOR]