Preliminary Functional Screening of Autochthonous Saccharomyces cerevisiae from Mexican Cocoa Bean Fermentation for...

Yeasts have attracted increasing attention as potential alternatives to traditional bacterial probiotic strains due to their physiological resilience and functional versatility. However, the probiotic potential of yeast strains associated with Mexican cocoa bean fermentation remains largely unexplored. Therefore, this study aimed to conduct a preliminary screening of physiological and surface-related traits associated with probiotic functionality in four autochthonous Saccharomyces cerevisiae strains (YCTA5, YCTA9, YCTA14, and YCTA16), previously isolated from cocoa fermentation, using Saccharomyces boulardii (Jarrow Formulas^®) as a reference strain. Evaluated parameters included tolerance to temperature, pH, and bile salts; hemolytic activity; survival in vitro under gastrointestinal (GI) conditions; bile salt hydrolase activity; auto-aggregation; co-aggregation; hydrophobicity; and response to antifungal agents (fluconazole, ciclopirox, nystatin, and clotrimazole). All yeast strains grew at 37 °C and at pH 4-8 and showed no hemolytic activity. All strains exhibited high auto-aggregation (>70%) and hydrophobicity values ranging from 55 to 88%. In the coaggregation assay, strains YCTA9, YCTA14, and YCTA16 showed moderate interactions with Escherichia coli, Bacillus cereus, and Listeria innocua, with some combinations exceeding 50%. Nevertheless, none of the yeast strains exhibited measurable growth at pH 2; bile salt tolerance was limited to 0.1% Oxgall, and viability decreased by approximately 54-56% after simulated gastrointestinal transit. These findings indicate that although some strains exhibited promising surface-related properties, significant physiological constraints restrict their probiotic potential under the tested conditions. Therefore, the studied yeast strains should be regarded as preliminary candidates requiring further validation. This work provides a first-stage evaluation for identifying functional yeast strains from Mexican cocoa bean fermentation, serving as a basis for future in vitro and in vivo studies.