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 <i>Lactobacillus</i>/<i>Bifidobacterium</i>-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 <i>Lactobacillus</i> and <i>Roseburia</i> while decreasing <i>Streptococcus</i> and <i>Staphylococcus.</i> These coordinated clinical, immunological, transcriptomic, epithelial, and microbiome changes support prophylactic protection by IBM against DSS colitis.