Characterization of Exopolysaccharides from Lactic Acid Bacteria using Edible Growth Medium

Exopolysaccharides (EPSs) are naturally occurring carbohydrates with various biological properties, including antimicrobial, antioxidant, anticancer, immunomodulatory, and gut microbiota-modulating properties, which have been extensively studied. Lactic Acid Bacteria (LAB) are constantly generating interest as a safe source of EPSs while posing no health risks. The present study aims to identify EPS-producing LAB isolates, determining the GRAS capability and EPS-producing potential; it also aims to assess the industrial applications of EPSs.

In this work, initially, EPS-producing LAB strains, including Lactiplantibacillus plantarum and Enteroccoccus faecium, were identified by a series of cultural, morphological, and molecular identification techniques. A comparative study of the bacterial growth condition revealed a higher growth rate of these LAB strains in the vegetable-based edible medium than in the MRS media. In a GRAS capability study focused on probiotic characteristics, the LAB strains were able to tolerate simulated human gastrointestinal (GI) tract conditions (a high temperature, low pH, and bile salt) and exhibited significant cell-surface hydrophobicity. The ethanol precipitation method was used for the extraction of EPSs followed by the purification of the EPSs by column chromatography and thin-layer chromatography (TLC). Maximum EPS yields of approximately 135-175 mg/500 mL were achieved after the anaerobic incubation of the LAB strains for 48h at 37°C under static conditions. UV-vis, FTIR, XRD, and NMR spectroscopy were subsequently performed on the purified EPSs to determine the purity, key functional groups, and the structure of the polysaccharides, respectively. The antimicrobial, antioxidant, and emulsification properties of the purified EPSs were assessed to evaluate their biological properties. The EPSs possessed antimicrobial activity along with stronger antioxidant and emulsification activity. Therefore, the biological and functional characteristics of the LAB EPSs support the potential use of EPSs in the food and pharmaceutical industries.