Functional features, composition, production optimization, and genomic insights into exopolysaccharide extracts produced by Lactiplantibacillus pentosus LP309

This study investigates the functional properties, composition, and production optimization of the exopolysaccharide (EPS) extracts synthesized by Lactiplantibacillus pentosus LP309, a strain isolated from table olive fermentations. The EPS extracts were produced in two media: MRS culture (MRS-309) and Manzanilla olive brine (SAL-309). Chemical analysis revealed that EPS extracts produced by LP309 are heteropolysaccharides formed mainly by glucose (41.58%), galactose (27.32%), and mannose (19.43%) in MRS-309, and only glucose (48.20%) and galactose (47.50%) in SAL-309. Regarding bioactivity, neither extract showed cytotoxicity in human macrophages at dosages below 50 μg/mL. In contrast, both exhibited significant antioxidant activity by reducing ROS production, with SAL-309 showing higher efficiency. Additionally, both EPS extracts also demonstrated anti-inflammatory effects by significantly decreasing TNF-α and IL-6 levels, results confirmed via western blot analysis of COX-2, Nrf-2, and HO-1 proteins. This work also modeled EPS production in MRS-309 medium as a function of pH, temperature, and salt concentration. The maximum predicted yield (527 mg/L) was achieved at 1.80% NaCl, pH 7.24, and 22.5–29.6 °C. Finally, genomic analysis identified two functional Wzx/Wzy-dependent biosynthesis clusters, one on the chromosome and one on the plasmid, confirming the ability to produce a structurally diverse heteropolysaccharide. In conclusion, the EPS extracts produced by LP309 show a significant potential for human nutraceutical applications, combined with its safe profile and established genomic basis for production. Therefore, this achievement presents a promising opportunity to employ LP309 as a starter culture in table olive fermentation and to exploit it further brines for EPS production.