Antilisterial and antioxidant exopolysaccharide from Enterococcus faecium PCH.25 isolated from cow butter: characterization and probiotic potential.

Exopolysaccharides produced by lactic acid bacteria have gained attention for their potential health benefits and applications in functional foods. This study explores the isolation and characterization of a novel exopolysaccharide-producing strain from dairy products. The aim was to evaluate its probiotic potential and investigate the properties of the produced exopolysaccharide. A strain identified as Enterococcus faecium PCH.25, isolated from cow butter, demonstrated exopolysaccharide production. The study's novelty lies in the comprehensive characterization of this strain and its exopolysaccharide, revealing unique properties with potential applications in food, cosmetic, and pharmaceutical industries. The E. faecium PCH.25 strain exhibited strong acid tolerance, with a 92.24% viability rate at pH 2 after 2 h of incubation. It also demonstrated notable auto-aggregation (85.27% after 24 h) and co-aggregation abilities, antibiotic sensitivity, and absence of hemolytic activity, suggesting its probiotic potential. The exopolysaccharide produced by this strain showed bactericidal activity (MIC and MBC = 1.8 mg/ml) against Listeria monocytogenes and antioxidant properties (22.8%). Chemical analysis revealed a heteropolysaccharide composed of glucose and fructose monomers, with various functional groups contributing to its bioactivities. Physical characterization of the exopolysaccharide indicated thermal stability up to 270 °C, a negative zeta-potential (-27 mV), and an average particle size of 235 nm. Scanning electron microscopy and energy dispersive X-ray analysis revealed a smooth, nonporous structure primarily composed of carbon and oxygen, with an amorphous nature. These findings suggest that the exopolysaccharide from E. faecium PCH.25 has potential as a natural antibacterial and antioxidant polymer for use in functional foods, cosmetics, and pharmaceuticals.