CHEMICAL, TECHNOLOGICAL AND BIOLOGICAL FEATURES OF AN EXOPOLYSACCHARIDE FROM LEUCONOSTOC MESENTEROIDES

Microbial exopolysaccharides (EPS) from lactic acid bacteria have received great interest in both the industrial and research fields, due to their technological properties (e.g., water binding capacity, stabilizers, ...) and biological activities (e.g., antimicrobial, antioxidant, ...) [1,2]. For this reason, the research of new EPS with peculiar technological properties and biological activity is of great interest. In this study, chemical characteristics, technological properties, and antimicrobial activity of an EPS (EPS_O) from a Leuconostoc mesenteroides strain of dairy origin were investigated. One- and two-dimensional NMR, DOSY and FT-IR revealed that EPS_O was a high molecular weight dextran (about 108 Da) with a very compact appearance, as evidenced by SEM. EPS_O was characterized by high water- and oil-holding capacity (784 and 496% respectively) and high solubility in water (about 99%). The thermal stability of EPS_O was also investigated by DSC analysis revealing the melting peak at 147 °C and the Tg at 83 °C. When EPS_O (50 mg/mL) was put in contact with water cold gelation occurred resulting in a weak gel as confirmed by rheological analysis. Antimicrobial activity of EPS_O was also investigated against Escherichia coli, Enterococcus faecium, Staphylococcus aureus, Salmonella enterica and Listeria monocytogenes through the observation of the turbidimetric growth kinetics. EPS_O displayed significant activity on L. monocytogenes decreasing the cell concentration at the end of the growth. All these characteristics could highlight the potential use of EPS_O as a promising ingredient to improve food characteristics and bioactivities.