Leuconostoc pseudomesenteroides YT830: a promising lactic acid bacterial starter culture for synbiotic fermented yak milk products as revealed by metabolic and genomic analyses.

This study aimed to isolate and characterize autochthonous lactic acid bacteria (LAB) from naturally fermented yak milk (NFYM) in the western Sichuan Plateau, focusing on their ability to metabolize diverse prebiotic oligosaccharides and their potential as synbiotic starter cultures with probiotic properties. Twenty LAB isolates representing eight species were obtained from eleven NFYM samples. Metabolic screening revealed strain- and species-specific utilization of seven prebiotic oligosaccharides. Leuconostoc pseudomesenteroides YT830 efficiently metabolized fructo- (FOS), xylo- (XOS), and isomalto-oligosaccharides (IMO), reducing pH to 5.13, 4.66, and 5.12, respectively, after 72 h. Whole-genome sequencing (2.17 Mbp, 2244 CDSs) identified 60 carbohydrate-active enzymes and 182 genes involved in carbohydrate transport and metabolism, along with multiple gene clusters for oligosaccharide degradation. Strain YT830 exhibited promising in vitro survival rates in simulated gastric (68.3%) and intestinal (90.7%) fluids, strong DPPH (95.9%) and hydroxyl radical (87.4%) scavenging, and antimicrobial activity against Escherichia coli and Staphylococcus aureus, and no transferable antibiotic resistance genes. Leu. pseudomesenteroides YT830 combines versatile oligosaccharide metabolism with favorable in vitro probiotic properties and a favorable safety profile, supporting its application as a starter culture for synbiotic fermented yak milk products.