Optimisation and characterization of α-D-glucan produced by Bacillus velezensis RSDM1 and evaluation of its protective effect on oxidative stress in Tetrahymena thermophila induced by H2O2

A novel exopolysaccharide was isolated from Bacillus velezensis RSDM1, purified and characterized. The optimization was carried out by Box-Behnken design and the highest yield of EPS-RSDM1 was 1969.53 mg/L. The EPS was composed by glucose with a molecular weight of 1.78 × 104 Da and connected by α-1,6 and α-1,3. The EPS was thermally stable and showed pseudoplastic rheology. The SEM have demonstrated a porous structure. Furthermore, EPS-RSDM1 showed a protective effect against the oxidative stress induced by H2O2 in Tetrahymena thermophila. The exposure of the cells to H2O2 reduced significantly the cell survival and CAT, SOD, GR, SDH and GAPDH activities, and increased the MDA production. However, pretreatment of the cells with EPS-RSDM1 prior to H2O2 exposure elevated the cell survival and enzyme activities, and decreased the level of MDA activity. Our study suggest that EPS-RSDM1 could be useful for preventing cellular oxidation in pharmaceutical and food industries.