The study aimed to identify potential sources of novel probiotic yeasts exhibiting health-promoting properties. A combination of metabarcoding analysis and cultural methods was employed to investigate and isolate yeasts from various sources, including rice wine, palm wine, fermented shrimp paste at different stages of natural fermentation, and lychee peels. The two analytical methods revealed distinct yeast profiles, and each source exhibited a unique composition of yeast species. Through metabarcoding and cultural methods, it was demonstrated that lychee peels harbored a greater diversity of genera compared to other sources. The evaluation of the probiotic properties of yeasts revealed that lychee peel yielded the highest proportion of isolates with potential probiotic activity (53.33%), followed by palm wine (25%), fermented shrimp paste (10%), and rice wine (9.09%). Moreover, yeast isolates with health-promoting properties as evaluated in this study, including Starmerella meliponinorum L12 and Pichia terricola L9 from lychee peels, demonstrated notable antioxidant activity and cholesterol-reducing properties, respectively. These findings represent the first report providing initial insights into the influence of yeast sources and serve as a guideline for the targeted selection of yeasts with specific probiotic and health-promoting attributes.

Long-term adherence to plant-based diets can modify gut bacterial microbiota composition and metabolite profiles, which may be particularly relevant for postmenopausal women who frequently adopt such diets and experience age-related changes in nutrient absorption and metabolism. Fermented foods, commonly consumed in vegetarian diets, enhance dietary diversity and nutritional quality. This study compared gut bacterial microbiota and fecal metabolomes between vegetarians (VGs) and omnivores (OMs) and evaluated the contribution of fermented food intake. Thirty-two healthy postmenopausal Thai women (>55 years; 16 VGs, 16 OMs) were enrolled. Gut bacterial microbiota and fecal metabolites were analyzed using 16S rRNA metagenomic and untargeted ¹H-NMR metabolomics. The five most frequently consumed fermented foods were microbiologically characterized. Fermented food consumption was found to be significantly different between groups. OM participants reported infrequent consumption (60% of weekly meals). VG participants exhibited enrichment of Prevotella, Faecalibacterium, and Blautia, while OM participants showed higher abundances of Bacteroides and Escherichia–Shigella. LEfSe identified Weissella as a bacterial taxon associated with the VG group. Functional prediction and metabolomic analyses indicated enhanced carbohydrate fermentation and increased short-chain fatty acid (SCFA) production in VGs, whereas OM profiles reflected greater protein catabolism. Fermented foods consumed by VGs shared microbial biomarkers with the VG gut bacterial microbiota and were rich in SCFAs and essential amino acids, supporting their potential role as microbial and metabolic contributors within the gut ecosystem and nutritional adequacy in postmenopausal vegetarians.