Exopolysaccharide Produced by Ligilactobacillus salivarius CRL 2217: Structure Insights and Functional Attributes

Exopolysaccharides (EPSs) produced by lactic acid bacteria have attracted increasing attention as multifunctional biopolymers owing to their structural diversity and technological and biological properties. However, despite the extensive use of Ligilactobacillus salivarius as a probiotic species, particularly in poultry production, its EPS-producing capacity remains poorly characterised. Here, we demonstrate that EPS production constitutes an additional value-added trait of the poultry probiotic strain L. salivarius CRL 2217. Response surface methodology identified 5% sucrose, initial pH 6.5, and 37 °C as optimal conditions, with a maximum crude EPS concentration of 1.40 mg/mL (glucose equivalents). EPS synthesis resulted in extracellular polymer accumulation without affecting wheat germ agglutinin binding. Monosaccharide analysis, GC, GPC-HPLC, FT-IR, Raman spectroscopy, and one- and two-dimensional NMR identified the polymer as a high-molecular-weight dextran (Mw > 1.5 × 106 Da) composed predominantly of α-(1→6)-linked D-glucopyranosyl residues with minor α-(1→3)-associated structural features. The EPS showed high water-holding capacity, water solubility, and stable emulsifying activity, as well as concentration-specific effects on neutral red uptake and nitrite production by RAW 264.7 macrophages, without cytotoxicity. These findings support the notion of dextran production as a distinct functional and biotechnological trait of CRL 2217.