Optimization, dynamics, and enhanced production of a free radical scavenging extracellular polysaccharide (EPS) from hydrodynamic sediment attached Bacillus megaterium RB-05

Extracellular polysaccharide production of Bacillus megaterium RB-05, a river sediment isolate, was optimized in glucose mineral salts medium by response surface methodology. Experimental maximum production (0.895 g l−1) was very close to the theoretical maximum value of 0.904 g l−1 after 25 h incubation at 33.3 °C and pH 7.62. The maximum specific growth rate and specific EPS production rate were calculated to be 0.65 h−1 and 0.215 g g−1 cell respectively. The growth yield coefficient and product yield coefficients were evaluated to be 0.13 g of biomass g−1 glucose, 0.065 g of EPS g−1 glucose, and 0.484 g of EPS g−1 biomass. Yields were enhanced up to 1.2 g l−1 with l-aspergine and d-biotin supplementation. EPS showed evidence of free radical scavenging in in vitro studies.