Production optimization, partial characterization and properties of an exopolysaccharide from Lactobacillus sakei L3

The production optimization, partial characterization and properties of an exopolysaccharide (EPS) from Lactobacillus sakei L3 were performed. Sucrose concentration, initial pH and inoculation volume were the most significant variables that improved the L3 EPS production in a three-level Plackett-Burman design. The maximum EPS yield of 69.65 g/L (2.16-fold greater than the original yield) was obtained under optimal conditions of 127.80 g/L sucrose, initial pH 6.87 and 3.15% inoculation volume. Chemical analyses revealed that the observed EPS bioactivity was mainly due to the sugar moieties. The chain conformation was characterized by the Congo red test, a β-elimination reaction and circular dichroism, which indicated that the L3 EPS exhibited a random coil structure and O-linkages in aqueous solution, and the EPS concentration did not alter the EPS chain conformation but did modify the hydrogen-bond interactions and chirality of the polysaccharide. The purified L3 EPS exhibited high water solubility, probiotic effects and emulsification activity. The L3 EPS at 2.0 mg/mL formed a highly active and stable emulsion with sunflower oil, with EA, ES₂₄, ES₄₈ and ES₇₂ indices of 62.30 ± 0.06%, 57.95 ± 0.18%, 42.73 ± 0.26% and 43.05 ± 0.08%, respectively. These results collectively describe a high-yield EPS with unique characteristics for exploitation in large-scale industrial food applications.