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

Abstract This study aimed to characterize and assess the immunomodulatory capability of exopolysaccharides (EPSs) isolated from Lacticaseibacillus casei AP and AG. In a batch fermentation model, L. casei AP produced 48 mg/L EPSs, whereas L. casei AG produced 62 mg/L EPSs. The percentages of total carbohydrates in EPSs from L. casei AP and L. casei 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 L. casei AP but absent in the EPSs produced by L. casei AG. After grown on standard MRS medium, the EPSs isolated from L. casei AP and L. casei 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.