Assessment of Potential Probiotic Yeasts Isolated from The Small Intestines of Cattle in Thailand

Y easts are widely studied and considered good candidates for probiotics due to their numerous benefits. This study aimed to investigate potential probiotic attributes of yeasts isolated from the small intestines of cattle in Thailand. Growth at body temperature, resistance to low pH, auto-aggregation capability, hydrophobicity, growth under gastrointestinal tract (GIT) conditions, safety profiles, antimicrobial activity, and extracellular enzyme production of yeast strains were evaluated in vitro. The results of sequential screening indicated that 829 out of 1,025 yeast strains could grow at both 37 and 39 °C, 682 strains could resist acidity at pH 2 for 24 h, 252 strains revealed greater than 83% auto-aggregation capability, and 97 strains showed higher than 90% hydrophobicity. Sixty strains grew well under simulated GIT conditions in the presence of pepsin, pancreatin, and bile salts. Thirteen strains of Diutina rugosa showed negative results for hemolytic, gelatinase, and phospholipase activities, while seven strains of Pichia kudriavzevii also showed negative results for the above activities, except for phospholipase. Neither D. rugosa nor P. kudriavzevii inhibited Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa. Additionally, 12 strains of D. rugosa and four strains of P. kudriavzevii produced phytase and cellulase, while only D. rugosa PCD3-6 exhibited protease and phytase activities. Therefore, D. rugosa (strains PCD3-6, PCD93-19, PYJ93-7, PYJ93-16, PCJ94-4, PCJ94-6, PCJ94-10, PYD100-8, CTD93-1, CTD93-2, CTJ93-5, CTJ93-6, and YTJ97-4) and P. kudriavzevii (strains PYI3-3, PCI3-4, PCJ90-7, and PYI91-15) were proposed as potential probiotic yeasts. They may be beneficially applied as feed additives to improve nutritional value and quality, thereby enhancing animal performance and health. Moreover, this work indicated useful preliminary results that could be a baseline for future research in human probiotic applications.