Effects of Lactobacillus paracei JY062 Postbiotic on Intestinal Barrier, Immunity, and Gut Microbiota

Research on postbiotics derived from probiotic fermented milk bases require further expansion, and the mechanisms through which they exert their effects have yet to be fully elucidated. This study utilized in vitro cell co-culture, digestion, and fermentation experiments, combined with targeted T500 technology, to elucidate the mechanism by which postbiotic Pa JY062 safeguards intestinal health. Compared to the LPS group, Pa JY062 boosted phagocytic ability in RAW264.7 macrophages, decreased NO levels, and alleviated LPS-induced excessive inflammation. Pa JY062 suppressed pro-inflammatory cytokines (IL-6, IL-17α, and TNF-α) while elevating anti-inflammatory IL-10. It prevented LPS-induced TEER reduction in Caco-2 monolayers, decreased FITC-dextran permeability, restored intestinal microvilli integrity, and upregulated tight junction genes (<i>ZO-1</i>, <i>occludin</i>, <i>claudin-1</i>, and <i>E-cadherin</i>). The hydrolysis rate of Pa JY062 progressively rose in gastrointestinal fluids in 0-120 min. At 5 mg/mL, it enriched gut microbiota diversity and elevated proportions of <i>Limosilactobacillus</i>, <i>Lactobacillus</i>, <i>Pediococcus</i>, and <i>Lacticaseibacillus</i> while augmenting the microbial production of acetic acid (120.2 ± 8.08 μg/mL), propionic acid (9.9 ± 0.35 μg/mL), and butyric acid (10.55 ± 0.13 μg/mL). Pa JY062 incorporated α_s-casein/β-lactoglobulin hydrolysate (L-glutamic acid, alanine, lysine, tyrosine, phenylalanine, histidine, and arginine) to mitigate protein allergenic potential while harboring bioactive components, including tryptophan metabolites, vitamin B6 (VB6), and γ-aminobutyric acid (GABA). Pa JY062 represented a novel postbiotic with demonstrated intestinal health-promoting properties. These findings advance the current knowledge on postbiotic-mediated gut homeostasis regulation and expedite the translational development of dairy-derived postbiotic formulations.