Mechanisms of Bifidobacterium animalis J12 in reshaping yogurt flavor homeostasis and alleviating constipation via the "metabolite-nerve-endocrine" framework.

The application of bifidobacteria in fermented dairy products is often limited by insufficient storage stability and unclear mechanistic links between microbial metabolism and host benefits. Here, we investigated the technological performance, aroma homeostasis, and constipation-alleviating mechanism of Bifidobacterium animalis J12 co-fermented yogurt (J12-Y). J12 co-fermentation maintained excellent physicochemical stability during 28 days of refrigeration, with viable counts remaining above 7.0 log CFU/mL and preserving the classical buttery-creamy aroma backbone, as evidenced by stable 2,3-butanedione (OAV ≈ 41-42). In a loperamide-induced constipation mouse model, J12-Y improved bowel function by shortening the time to first black stool (approximately 110 vs. 131 min), increasing fecal water content (approximately 56% vs. 28%), and enhancing intestinal transport rate (approximately 67% vs. 45%) relative to the model group. Mechanistically, J12-Y was associated with a coordinated cascade of metabolic and neuroendocrine events. Fecal metabolomics revealed robust enrichment of short-chain fatty acids (SCFAs), particularly acetate, propionate, and butyrate, alongside modulation of indole derivatives and bile acid-related metabolites. These metabolic shifts were accompanied by a pro-motility neuroendocrine profile, characterized by elevated excitatory neurotransmitters and hormones (5-HT, ACh, SP, GAS, MTL) and reduced inhibitory signaling (SS, VIP). Spearman correlation analysis further revealed critical functional links: butyric acid showed strong positive correlations with 5-HT (r = 0.62) and intestinal transport rate (r = 0.80); acetic acid was positively correlated with fecal water content (r = 0.67); and deoxycholic acid exhibited negative correlations with intestinal transport rate (r = -0.82) and 5-HT (r = -0.74). Collectively, these findings support a proposed "metabolite-nerve-endocrine" framework in which J12-Y mediates relief of constipation through integrated microbial metabolic and neuroendocrine modulation. Overall, B. animalis J12 represents a promising adjunct culture that couples aroma stability with constipation-relieving potential through integrated microbial metabolic and neuroendocrine modulation.