Antioxidant property and structural characteristics of exopolysaccharides derived from Lactiplantibacillus plantarum VAL6

The novel exopolysaccharides (EPS) derived from Lactiplantibacillus plantarum VAL6, a species of lactic acid bacteria isolated from fermented vegetable samples in Vietnam, show promising potential as a natural alternative to commercial additives. Among the six isolates, L. plantarum VAL6 exhibited remarkable EPS production, reaching 5.72 g/L, surpassing other isolated strains. The characteristics of the EPS extracted from L. plantarum VAL6 were determined through Nuclear Magnetic Resonance (NMR) analysis and Gas Chromatography with Flame-Ionization Detection. The monosaccharide composition of the EPS was found to contain mannose, glucose, rhamnose, and galactose in molar ratios of 71.98: 23.41: 2.54: 2.07. NMR analysis revealed the presence of both alpha and beta configurations of sugar residues in the EPS structure. In vitro antioxidant activity testing demonstrated that the EPS exhibited significant antioxidant properties, with 2,2-Diphenyl-1-(2,4,6-trinitrophenyl) hydrazyl free radical scavenging capacity of 14.07 µmol TE/g and a total antioxidant capacity of 8.00 (mg AAE/g). The simultaneous presence of both alpha and beta configurations, combined with the high mannose content in the molecular structure of the EPS produced by L. plantarum VAL6, may be the key factors governing their observed antioxidant properties. These findings collectively indicate that the EPS produced by L. plantarum VAL6, as a natural compound, holds great potential for development as a natural antioxidant or functional additive in the food industry.