Screening of xylo-oligosaccharide-utilizing lactic acid bacteria from yak calves and characterization of Limosilactobacillus mucosae YT200

AIMS: This study aimed to investigate the capacity of lactic acid bacteria (LAB) isolated from yak calves to metabolize xylo-oligosaccharides (XOS) and to identify potential probiotic strains that could enhance the gut health of yak calves. METHODS AND RESULTS: LAB isolates were recovered from 15 fecal samples collected from yak calves. Their capacity to utilize XOS as the sole carbon source was evaluated, and their metabolic characteristics, molecular mechanisms, and functional properties associated with XOS metabolism were examined through integrated phenotypic and genomic analyses. Consequently, 41 LAB isolates were identified from 10 of the 15 yak calves and tested for XOS utilization. Among these, 51.22% (21/41) exhibited species- and strain-specific XOS utilization, including Limosilactobacillus mucosae (10 isolates), Lactobacillus brevis (10 isolates), and Lactiplantibacillus plantarum (1 isolate). Limosilactobacillus mucosae YT200 showed the highest acid production (pH 4.50) and short-chain fatty acid accumulation, particularly acetic acid (745.00 ± 16.24 mM). Genomic analysis revealed three gene clusters encoding GH43 α-L-arabinofuranosidase, GH51 α-L-arabinofuranosidase, and GH43 β-xylosidase, enabling the hydrolysis of arabinosyl-substituted and linear XOS. Strain YT200 also demonstrated antagonism against common gut pathogens including Escherichia coli and Staphylococcus aureus, sensitivity to seven antibiotics, and no transferable resistance genes. CONCLUSION: This study reveals the mechanistic basis of XOS metabolism in L. mucosae YT200 and identifies L. mucosae YT200 as a promising candidate for synbiotic development.