Characteristics of Two Saccharomyces cerevisiae Strains and Their Extracellular Vesicles as New Candidates for Probiotics.

There is a huge disparity between the number of bacterial and yeast probiotics in favor of the former. The latest reports indicate that extracellular vehicles (EVs) play a significant role in probiotic mechanisms. In the present work, we compared the probiotic properties of Saccharomyces cerevisiae strains (WUT3 and WUT151), which have never been previously characterized in this context, with commercial probiotic yeast-Saccharomyces cerevisiae var. boulardii CNCM-745. Notably, WUT3 and WUT151 reacted more mildly to the unfavorable simulated environment of saliva, stomach, small, and large intestines. As a result, we confirmed that WUT3 and WUT151 were superior to S. boulardii in terms of probiotic properties. Then, we performed a complex analysis of their EVs, isolated by a multistep filtration process. The nanoparticle tracing analysis showed no significant difference in the diameter of the vesicles between the strains. MTT studies confirmed that EVs are not toxic against normal human colorectal cell lines CCD-18 Co and CCD 841 CoN. However, toxicity was observed against the HT-29 cancer line. By staining EVs with Nile Red, we successfully visualized EVs-cell interactions. Finally, we explored the profile of proteins transported with the EVs, identifying a significant overrepresentation of extracellular proteins. Based on comparison with other proteomic data, we selected marker proteins for S. cerevisiae EVs. This knowledge will be helpful for further studies on tracking the transfer of the protein cargo of yeast EVs to human cells using, for instance, specific antibodies to these marker proteins.