Characterization of Zygosaccharomyces bailii KAV1 Isolated from Kombucha: A Promising Yeast for Human Health Modulation

Kombucha is a fermented beverage obtained from sweetened tea, characterized by a complex microbial consortium primarily composed of yeasts and acetic acid bacteria. This study originates from the characterization of the kombucha microbiota, with the aim of investigating its potential impact on human health through probiotic, paraprobiotic, or postbiotic activities. Given the limited characterization of probiotic yeasts, our attention was focused on Zygosaccharomyces bailii strains we isolated from kombucha, aiming at evaluating their probiotic or postbiotic potential. Z. bailii is frequently found in food matrices and, although historically considered a spoilage organism, it is also involved in desired fermentations such as those of wine and kombucha. We primarily assessed the safety of the kombucha isolate Z. bailii KAV1, showing that it belongs to BioSafety Level 1 and does not display hemolytic activity on blood agar plates. Subsequently, antioxidant activity was evaluated using the DPPH assay and catalase activity quantification. GC-MS analysis of fermentation products revealed the production of notable amounts of butyrate and other short-chain fatty acids (SCFAs). Finally, immunomodulatory effects were assessed on human peripheral blood mononuclear cells (PBMCs), showing a significant reduction in TNF-α production. These preliminary findings suggest that Z. bailii KAV1 may have a beneficial modulatory effect on human health and could represent a promising candidate as a probiotic yeast.