Surface Properties and Potential Immunomodulatory Effects of Candidate Probiotic Lactobacilli for Gastrointestinal Applications

Aim: This study was aimed at evaluating the adhesive and immunomodulatory properties of indigenous lactobacilli strains isolated from fermented foods, infant feces, and human milk. Methodology: The adhesive properties of lactobacilli strains were evaluated for hydrophobicity, coaggregation, and autoaggregation capacities. The best strains were evaluated for adhesion to HT‐29 cell line in the presence of lipopolysaccharides. Further, the best performing strains were evaluated in post, pre, and coculture methods for modulation of cytokine release and their expression in cell through RT‐qPCR and ELISA, respectively. Results: The test lactobacilli strains showed strong affinity toward toluene compared to hexadecane. Seven of the strains, namely, 3ST3, 3ST7, 8BM6, 8ST7, BK5, GR27, and GR8, were strongly (> 60%) hydrophobic toward both the solvents. Strains belonging to the Lacticaseibacillus casei group (3ST5, 72%; PT1, 64.33%; and 3BM4, 60%), except Lacticaseibacillus paracasei BK5, showed promising autoaggregation. The majority of strains displayed marked coaggregation within the ranges of 50%–70%, significantly higher than probiotic Lacticaseibacillus rhamnosus GG (LGG) (33%). Qualitative adhesion revealed that strain Lactiplantibacillus pentosus 15ST2 exhibited the highest rate of adhesion (45.33%) around the edges and surface of the HT‐29 cells. Most of the lactobacilli significantly ( p < 0.05) inhibited Staphylococcus aureus by exclusion interference. During transcriptional studies, a significant upregulation in the expression of TLR2 and the proinflammatory marker TNF -α was observed for KN3 (14.08‐fold) and the 3BM3 strain (7.76‐fold) in the coculture model. While in pre‐ and postculture, no significant difference in the expression of TLR2, TNF‐ α , and IL‐10 was recorded in comparison to LPS‐stimulated cells. The proinflammatory cytokine IL‐8 was upregulated during pre‐ and postculture conditions at both transcription and translation levels. Conclusion: The indigenous lactobacilli (15ST2, 3BM3, and KN3) strains effectively adhered to intestinal cell surface and thereby have shown their potential to modulate the production of proinflammatory cytokines at both transcription and translation levels, when introduced alongside pathogens or established before bacterial infection.