Probiotic potential and exopolysaccharide characterization of two native lactic acid bacteria for functional applications

This study investigates the probiotic potential of two native lactic acid bacteria (LAB) strains, Leuconostoc pseudomesenteroides UTNElla29 (Ella29) and Weissella confusa UTNCys2-2 (Cys2-2), isolated from fruits. Standardized methodologies were employed to assess their resistance to synthetic gastric juice, bile salts, and sodium chloride, as well as their hydrophobicity, auto-aggregation capacity, hemolytic activity, and antibiotic susceptibility. Additionally, exopolysaccharides (EPSs) were analyzed for cytotoxicity, antioxidant activity, and structural composition using proton nuclear magnetic resonance ( 1 H NMR) and attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy. Both strains demonstrated substantial resilience under acidic gastric conditions and bile salt exposure, with Ella29 showing superior bile tolerance. Both also thrived in high-sodium environments, with Cys2-2 exhibiting greater salt tolerance, highlighting their ability to survive in the gastrointestinal tract. Hydrophobicity and auto-aggregation increased over time, indicating enhanced cell-cell interactions, critical for adhesion and colonization. Neither strain exhibited hemolytic activity, reinforcing their safety as probiotics. Their antibiotic susceptibility profile revealed intrinsic resistance to kanamycin, gentamycin, and vancomycin while maintaining high susceptibility to β-lactam antibiotics, minimizing the risk of antibiotic resistance gene dissemination. While Cys2-2 displayed slightly higher cytotoxicity, Ella29 exhibited superior cell viability, making it preferable for applications requiring preserved cellular integrity. Antioxidant assays demonstrated stronger radical scavenging activity in Cys2-2. Structural characterization of EPSs identified key biomolecular components, including proteins, lipids, carbohydrates, and nucleic acids. The distinct biochemical properties of EPSs from Ella29 and Cys2-2 highlight their potential for diverse industrial and functional food applications, warranting further investigation. • Both Ella29 and Cys2-2 show strong resistance to gastric and bile conditions. • Cys2-2 exhibits higher salt tolerance, while Ella29 maintains superior cell viability. • Cys2-2 demonstrates higher antioxidant activity due to S-type sugars and functional groups. • ATR-FTIR and NMR analyses reveal distinct exopolysaccharide properties for industrial applications.