The immunomodulatory properties of exopolysaccharides (EPSs) produced by Streptococcus thermophilus have not been explored in depth. In addition, there are no comparative studies of the functional properties of EPSs produced by streptococci in different food matrices. In this work, EPSs from S. thermophilus SBC8781 were isolated after soy milk (EPS-s) or cow milk (EPS-m) fermentation, identified, and characterized in their abilities to modulate immunity in porcine intestinal epithelial cells. Fresh soy milk and cow milk were inoculated with S. thermophilus SBC8781 (7 log CFU/mL) and incubated at 37 °C for 24 h. The extraction of EPSs was performed by the ethanol precipitation method. Analytical techniques, including NMR, UV-vis spectroscopy, and chromatography, identified and characterized both biopolymer samples as polysaccharides with high purity levels and similar Mw. EPS-s and EPS-m had heteropolysaccharide structures formed by galactose, glucose, rhamnose, ribose, and mannose, although with different monomer proportions. On the other hand, EPS-s had higher quantities of acidic polymer than EPS-m. The biopolymer production of the SBC8781 strain from the vegetable culture broth was 200–240 mg/L, which was higher than that produced in milk, which reached concentrations of 50–70 mg/L. For immunomodulatory assays, intestinal epithelial cells were stimulated with 100 µg/mL of EPS-s or EPS-m for 48 h and then stimulated with the Toll-like receptor 3 agonist poly(I:C). EPS-s significantly reduced the expression of IL-6, IFN-β, IL-8, and MCP-1 and increased the negative regulator A20 in intestinal epithelial cells. Similarly, EPS-m induced a significant reduction of IL-6 and IL-8 expressions, but its effect was less remarkable than that caused by EPS-s. Results indicate that the structure and the immunomodulatory activity of EPSs produced by the SBC8781 strain vary according to the fermentation substrate. Soy milk fermented with S. thermophilus SBC8781 could be a new immunomodulatory functional food, which should be further evaluated in preclinical trials.

Lacticaseibacillus (L.) rhamnosus CRL75 is a lactic acid bacterium (LAB) isolated from local dairy products, demonstrating significant adaptation in skimmed milk (FM75). In this context, CRL75 exhibited high microbial growth (3.63 ± 0.18 log CFU·mL⁻¹), strong acidification (9.20 ± 0.10 g·L⁻¹ lactic acid, and 2.40 ± 0.10 pH units), and increased viscosity in FM75 after 16 h of fermentation. Additionally, this LAB strain produces both capsular polysaccharides (CPS+) and extracellular polysaccharides (EPS75), contributing to a ropy phenotype (>10 cm). The purified EPS75 (70.70 ± 3.25 mg·L⁻¹) displayed low molecular weight (12.7 kDa), with galactose and glucose as its primary monomers in a 4:1 ratio. In aqueous environments, EPS75 exhibited an extended size (147 nm), a random coil structure, and macromolecular aggregation. Furthermore, vibrational spectroscopy confirmed the presence of a neutral EPS with high thermal stability. Additionally, EPS75 exhibited dose-dependent antioxidant activity, effectively reducing metal ions (Fe³⁺, Mo⁶⁺, and Mn⁷⁺) and stabilizing radicals (ABTS^•+, HO^•, O₂^•−, and HOO^•). The biopolymer also demonstrated immunostimulatory and anti-inflammatory effects in RAW 264.7 cells. In vivo assays using Balb/c mice indicated that both EPS75 and FM75 prevented constipation, suggesting their potential as natural and safe agents for constipation-related disorders. Due to its viscosifying and health-promoting attributes, CRL75 offers promising applications for functional dairy products.