Characterization and bioactivities of a novel exopolysaccharide from Leuconostoc mesenteroides

Recently microbial exopolysaccharides (EPS) from lactic acid bacteria (LAB) have gained interest not only for their technological features but also for their health-promoting properties (Rahbar Saadat et al., 2019). Hence, the screening of novel EPSs with specific bioactivities and health-promoting effects is of great importance for the development of new value-added products (Lynch et al., 2018). In this study, a new EPS produced by Leuconostoc mesenteroides strain B3 isolated from a semi-hard Italian cheese was chemically and biologically characterized. 1H, 13C NMR, DOSY, FT-IR, and UV experiments revealed that EPS-B3 is a mixture of two high-molecular-weight dextrans (7.6 x 106 Da and 5.1 x 105 Da, respectively). SEM images evidenced a sheet-like appearance of the polymer. EPS-B3 displayed a significant antibacterial activity at 2.5 mg/mL against eight foodborne pathogens and inhibited the biofilm formation by Listeria monocytogenes. EPS-B3 also evidenced bifidogenic activity, stimulating the growth of three probiotic bifidobacteria, and improved the tolerance of Bifidobacterium animalis subsp. lactis to oxygen stress. It also displayed the ability to protect plasmid DNA from oxidative damage. Only limited antioxidant capacity was observed. These results indicated that EPS-B3 could be exploited in the context of functional food especially for its marked antimicrobial activity as well as for the ability to improve the viability of bifidobacteria in probiotic foods. Thus, it could be considered a promising ingredient in functional foods.