Investigating the Bioactivities of a Dextran and Levan Mixture Produced by the Sourdough-Derived Leuconostoc mesenteroides Strain DSA_F

Research of lactic acid bacteria (LAB) capable of producing exopolysaccharides (EPS) and their characterization is of great interest due to the many potential applications of these polymers, including various bioactivities. The properties of each EPS are strongly related to its structural features and the EPS-associated genes within each LAB-producing species and strain. This study aimed to structurally characterize and investigate the bioactivities of an EPS (EPS_F) produced by Leuconostoc mesenteroides DSA_F isolated from sourdough. The chemical characterization revealed that EPS_F was a mixture of dextran and levan with high molecular weight. EPS_F hindered the growth of selected foodborne pathogens (Escherichia coli, Salmonella enterica, Enterococcus faecium, and Listeria monocytogenes) and inhibited biofilm formation by List. monocytogenes and Pseudomonas fluorescens. EPS_F demonstrated antioxidant activity, suggesting its possible use as an antioxidant agent in foods. Furthermore, it provided mild protection to DNA from oxidative damage. This study represents the first evaluation of various bioactivities of a combination of dextran and levan and could lay the foundation for the possible exploitation of EPS_F as an antimicrobial and antioxidant agent. However, an in-depth investigation of mechanisms underlying the bioactivities observed should first be conducted.