Postbiotic Metabolites from a 31-Strain Lactobacillus/Bifidobacterium Co-Culture Attenuate DSS Colitis with Barrier- and Circadian-Linked Transcriptomic Signatures

Postbiotics produced by beneficial bacteria are emerging as safe dietary approaches to intestinal inflammation. We evaluated intestinal bacterial metabolites (IBM), a cell-free fermented soybean extract generated by co-culturing 31 Lactobacillus/Bifidobacterium-related strains, for prophylactic protection in 3% dextran sulfate sodium (DSS)-induced colitis. Male C57BL/6NJ mice received oral IBM (0.4 or 2 mL/kg/day) or vehicle for 7 days before and during 7 days of DSS. Disease activity index (DAI), colon length, and histopathology were assessed, and endpoint serum cytokines were quantified by a multiplex bead assay. DSS-independent responses were examined in healthy mice after 7 days of IBM by rectal RNA sequencing and cecal 16S rDNA profiling, and direct epithelial effects were tested in HCT-116 and DLD-1 cells treated with 2% IBM. IBM attenuated colitis, improving DAI, preventing colon shortening, and ameliorating histopathology, with decreased IL-23 and IL-17A and increased IFN-β and GM-CSF. Rectal transcriptomics showed modulation of circadian programs, upregulation of mucosal/barrier genes, and reduced extracellular-matrix remodeling signatures. IBM increased junctional proteins and barrier-related transcripts in vitro and shifted the microbiota, increasing Lactobacillus and Roseburia while decreasing Streptococcus and Staphylococcus. These coordinated clinical, immunological, transcriptomic, epithelial, and microbiome changes support prophylactic protection by IBM against DSS colitis.