Optimization and Characterisation of Thermo Stable Exopolysaccharide Produced from Bacillus licheniformis WSF-1 Strain

Bacillus licheniformis WSF-1 strain isolated from sugar distillery plant was capable of producing a maximum amount of EPS (1.24 g/mL) and dry biomass (3.25 g/mL) respectively. Certain factors like inoculum age and carbon source was standardised in view of obtaining high EPS yield. In this study, 48-h-old culture was identified as the optimum inoculum age for EPS production. In fermentation, as carbon source plays a major contributing factor that influences the EPS production, optimum carbon source was determined by studying the effect of different carbohydrates such as 12% of glucose, sucrose, lactose, maltose, xylose and fructose on EPS production. The best carbon source was identified as sucrose at a concentration of 25% producing 2.9 g/mL of exopolysaccharide. The polysaccharides were hydrolysed and the monomeric components were determined as fructose and glucose by HPLC, followed by FT-IR analysis. The thermal study revealed that the EPS can withstand high temperature of 219.4 °C and had high glass transition temperature of 150.6 °C. These features indicate the thermo stable nature of the exopolysaccharide which can be used for various industrial applications.