Abstract
Traditional fermented foods and beverages are important sources of probiotic microbes. The purpose of this study was to isolate yeast from Ethiopian fermented beverages and assess their probiotic activity in an in vitro setting. Yeast isolation, identification, and in vitro probiotic trait screening were conducted in accordance with established protocols. Eleven isolates were obtained. Of them, GB1D5, RTj3D3 and DMTD2 were low hydrogen sulfide producers and were selected. The D1/2 genotyping of selected isolates revealed that they were strains of Saccharomyces cerevisiae. All strains grew well at low pH, body temperature, bile salt concentrations (0.3-0.6 (w/v)) and survived at simulated gastrointestinal conditions with survival percentages of 12.8 ± 4.9 to 14.4 ± 5.0 % and 5.3 ± 1.7-5.9 ± 1.8 %, respectively. They demonstrated surface hydrophobicity ranging from 61.3 to 68.7 %; and 80.7-86 % auto-aggregation percentages after 24 h of incubation. They also showed hydroxyl radical scavenging activity ranging between 91.6 and 92.3 % and mild inhibitory activity against Escherichia coli (ATCC 893614) and Staphylococcus aureus (ATCC 892760). The PCA revealed that two strains (DMTD2 and RTj3D3) have a strong association with most probiotic properties, which affirms their promising candidacy. Safety assessments indicated that they were resistant to antibacterial antibiotics, susceptible to antifungals, and negative for protease, gelatinase, biogenic amine production, and hemolytic activity. All these suggest that they are promising candidates for the production of food containing probiotics. Examining their performance in vivo circumstances is recommended.