During the 13th Probiotics, Prebiotics and New Foods Congress, Microbiomepost.com conducted an exclusive interview with Duccio Cavalieri, professor at the University of Florence. This video interview shifts the spotlight from bacteria to the less-explored fungal and yeast communities of the microbiome, highlighting their emerging role in shaping host immunity—particularly via mechanisms of innate “trained immunity.”

The discussion focuses on Saccharomyces cerevisiae, a microorganism historically associated with food fermentation (bread, beer, and wine), now reconsidered through two decades of advances in cell-wall biology and genetics. A central concept is that cell-wall architecture—especially the chitin-to-mannan balance—may influence the activation of distinct immune responses, supporting a rational approach to strain selection and to distinguishing beneficial strains from potentially harmful ones.

The interview also revisits a common critique of S. cerevisiae probiotics: limited intestinal colonization. Rather than being a drawback, transient passage is presented as a potential ecological advantage, helping to promote the growth of Lactobacillus species relevant not only for gut health but also for vaginal and skin ecosystems, while counteracting overgrowth of key enteric pathobionts and pathogens such as Klebsiella, Escherichia coli, and Shigella. From this perspective, future probiotic consortia may intentionally include selected Saccharomyces strains as functional members of a broader microbial ecosystem. Finally, Saccharomyces boulardii—widely used for traveler’s diarrhea—is framed as merely the “tip of the iceberg,” pointing to a broader, still underexplored yeast-based probiotic pipeline.