Characterization and immunomodulatory activity of exopolysaccharides produced by Lacticaseibacillus casei strains on macrophage cultures

This study aimed to characterize and assess the immunomodulatory capability of exopolysaccharides (EPSs) isolated from <i>Lacticaseibacillus casei</i> AP and AG. In a batch fermentation model, <i>L. casei</i> AP produced 48 mg/L EPSs, whereas <i>L. casei</i> AG produced 62 mg/L EPSs. The percentages of total carbohydrates in EPSs from <i>L. casei</i> AP and <i>L. casei</i> AG were 79.40 and 81.17%, respectively. Monosaccharide composition analysis revealed the presence of ribose and glucose in EPSs produced by both strains. Fourier transform infrared (FTIR) spectroscopy confirmed the presence of hydroxyl, carboxyl, and amide groups. EPS microstructures showed coarse surfaces, with the main constituents being C, N, O, and Ca. In addition, P was present in the EPSs produced by <i>L. casei</i> AP but absent in the EPSs produced by <i>L. casei</i> AG. After grown on standard MRS medium, the EPSs isolated from <i>L. casei</i> AP and <i>L. casei</i> AG exhibited different immunomodulatory activities. These EPSs effectively increased the phagocytic and nitride oxide production of RAW 264.7 cells without toxic effects at concentrations between 50 and 800 μg/mL, suggesting that these strains are interesting producers of EPSs, which could be used in various potential applications in the food and pharmaceutical industries.