In Vitro Probiotic Characterization of Yeasts with their Postbiotics' Antioxidant Activity and Biofilm Inhibition Capacity

This study evaluated the in vitro probiotic potential and postbiotic properties of yeast strains isolated from traditional fermented foods, emphasizing antioxidant activity (AOA) and biofilm inhibition capacity (BIC). The yeasts were molecularly confirmed using start codon targeted polymorphisms as Kluyveromyces lactis (n = 17), Saccharomyces cerevisiae (n = 9), Pichia kudriavzevii (n = 6), P. fermentans (n = 4), Wickerhamomyces anomalus (n = 2), and Torulaspora delbrueckii (n = 1). The probiotic assessment of live cells included viability in simulated gastric and pancreatic juices, autoaggregation, hydrophobicity, and AOA, using S. boulardii MYA-796 as reference. Additionally, cell-free supernatants (CFS) were tested for AOA and BIC against Cronobacter sakazakii, Listeria monocytogenes, Pseudomonas aeruginosa, and Staphylococcus aureus. Several strains exhibited significantly higher in vitro probiotic characteristics compared to S. boulardii MYA-796 (P < 0.05), particularly in gastric and pancreatic survival, hydrophobicity, and AOA. Notably, CFS exhibited greater AOA than live cells and strong BIC, especially against L. monocytogenes and S. aureus. Multivariate analysis identified K. lactis TC11, S. cerevisiae M33T1-2, P. kudriavzevii S96, W. anomalus OB7Y1, and T. delbrueckii KY31 as having superior probiotic properties, attributed to enhanced gastric survival, autoaggregation, and AOA. CFS of S. cerevisiae M33T1-2 and T. delbrueckii KY31 demonstrated significant BIC, with over 60% inhibition across all tested pathogens.