Statistical modeling and optimization for exopolysaccharide production by Lactobacillus confusus in submerged fermentation under high salinity stress

Abstract

In the last two decades, many studies have been reported that a high concentration of NaCl suppresses exopolysaccharide (EPS) production in lactic acid bacteria. In the present study, however, the enhancement of EPS production by Lactobacillus confusus under high salinity stress in submerged fermentation was demonstrated using response surface methodology via a full factorial design. Under the optimized conditions of 3.33% NaCl, 20 g/L sucrose, and 35 h of incubation, the EPS yield was 10.87 g/ L with 178% higher than the maximum yield (6.12 g/L of EPS) produced from the modified MRS medium without NaCl. Biomass production was independent of EPS production. A high yield of biomass was obtained in the culture with 0.23% NaCl. This results indicate that high salinity stress by NaCl can enhance EPS production in submerged fermentation in uncontrolled pH cultivations by inducing the production of cell-associated dextransucrase.