Determination of the Probiotic and Functional Properties of Yeasts Isolated from Different Dairy Products

This study aimed to explore new probiotic yeast strains, considering that Saccharomyces cerevisiae is the only yeast used industrially. To this end, yeasts were isolated from various dairy products and their probiotic potential was investigated. All yeast strains demonstrated survival potential under simulated gastrointestinal conditions, mimicking the stomach and intestinal passage. Among the isolates, 13.04% were identified as moderate biofilm producers, 34.78% as weak biofilm producers, and 52.17% exhibited no biofilm-forming ability. Catalase enzyme production was detected in all isolates, and it was determined that their hydrophobicity varied depending on hydrocarbon interactions. In this study, the percentage of autoaggregation increased with prolonged incubation times across all strains. After 24 h, the percentage of autoaggregation exceeded 60% for all isolates. It was concluded that the coaggregation ability depended on incubation time and strain type. Most of the isolated yeasts exhibited antimicrobial activity against E. coli ATCC 25922, E. coli O157:H7, B. cereus, C. sakazakii ATCC 29544, L. monocytogenes ATCC 7644, S. aureus ATCC 25923, and S. typhimurium ATCC 140828. Furthermore, the yeast strains were resistant to all tested antibiotics. The 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity revealed that the antioxidant activity of the cells was higher than that of their intracellular extracts for all tested strains. The yeasts were initially identified using MALDI-TOF and further characterized through 18S-28S rRNA analysis. There are not many recent studies on the selection of probiotic yeasts for use in the dairy industry. Therefore, in this study we wanted to investigate some functional properties of different yeasts to be proposed as probiotic cultures in this specific sector. In particular, the antimicrobial and antioxidant properties and enzymatic activity highlighted by isolates have promising implications for food safety and health. These preliminary results provide a valuable basis for the future industrial application of probiotic yeasts in the dairy sector.