A Novel Weizmannia coagulans Strain WC412 with Superior Environmental Resilience Improves Growth Performance of Mice by Regulating the Intestinal Microbiota

The growing demand for sustainable and antibiotic-free animal production has intensified interest in probiotics as functional feed additives. In this study, novel strains of <i>Weizmannia coagulans</i> (WC412 and WC413) were isolated from pickle water-a previously unexplored source for probiotic screening. These isolates, along with three reference strains (<i>W. coagulans</i> S8, S15, and S17), were evaluated for their tolerance to heat, acid, and bile salts. Strain WC412 exhibited superior environmental resilience, as validated by principal component analysis (PCA) for comprehensive stress-tolerance assessment, and was selected for further investigations. A murine model was employed to assess the physiological and microbiological impacts of WC412 supplementation at varying doses. Medium-dose (1 × 10⁷ CFU·mL^-1) administration significantly improved body weight gain by 13% (<i>p</i> < 0.05), modulated serum lipid profiles, and increased antioxidant enzyme activity and IgG/IL-2 levels (<i>p</i> < 0.05). Notably, WC412 uniquely enriched beneficial genera (e.g., <i>Fructilactobacillus</i> and <i>Limosilactobacillus</i>) and promoted metabolic pathways linked to short-chain fatty acid production, as revealed by 16S rDNA sequencing and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis. These findings highlight WC412 as a robust probiotic candidate for enhancing animal growth performance and gut health through novel microbiota-mediated mechanisms.