Bifidobacterium animalis ssp. lactis BX-245-Fermented Milk Alleviates Inflammatory Bowel Disease by Modulating the Gut Microbiota and Metabolite Profile

Probiotic fermented milk, as a bioactive functional food, has gained growing interest for its potential to alleviate inflammatory bowel disease (IBD) through gut microbiota modulation. To clarify the mechanism of action of Bifidobacterium animalis ssp. lactis BX-245 (BX-245) fermented milk in mitigating IBD, a dextran sulfate sodium (DSS)-induced mouse colitis model was employed to systematically compare the effects of BX-245 bacterial powder, BX-245-fermented milk, and normal fermented milk. All three interventions markedly improved colitis symptoms, restored colonic tissue integrity, and reduced systemic inflammation. Mechanistically, BX-245 and its fermented milk formulation enhanced gut microbial diversity and elevated beneficial metabolites, especially short-chain fatty acids (SCFAs) and secondary bile acids—both of which play a key role in intestinal homeostasis and immune regulation—with oral gavage of BX-245 powder increasing the intestinal levels of butyric acid, pentanoic acid, and ursocholic acid in IBD mice to 1.9-fold, 2.9-fold, and 1.8-fold of their previous levels, respectively. Importantly, BX-245 was detected in the intestinal tract with a high abundance, and it promoted the enrichment of beneficial bacteria including Bifidobacterium animalis. These findings not only elucidate how BX-245-fermented milk alleviates IBD via the microbiota–metabolite axis, but also support the development of targeted functional dairy products designed to modulate gut microecology.