Molecular Genetics and Probiotic Mechanisms of Saccharomyces cerevisiae var. boulardii.

Saccharomyces cerevisiae var. boulardii (Sb) is a S. cerevisiae (Sc) strain that has been widely used in the treatment of gastrointestinal diseases due to its unique probiotic properties. The key genomic differences that distinguish Sb from Sc include the tetrasomy of chromosome XII, the absence of intact transposon-yeast (Ty) elements, and variations in the copy number of specific genes. These genomic variations may contribute to enhanced thermotolerance, increased acid resistance, and elevated acetate production, collectively supporting its probiotic functions. The probiotic mechanisms of Sb are mediated through luminal actions, mucosal actions, and trophic effects. Its luminal activity involves neutralizing pathogen toxins via the secretion of proteins and inhibiting pathogen growth through the production of short-chain fatty acids (SCFAs). Additionally, Sb modulates gut microbiota composition by fostering symbiotic relationships, thereby increasing the abundance of beneficial microbes and SCFA levels to promote gut health. The mucosal action of Sb promotes anti-inflammatory responses by regulating the nuclear factor kappa B (NF-κB) and mitogen-activated protein kinase (MAPK) pathways. Meanwhile, its trophic effects, driven by polyamine production, enhance the function of intestinal epithelial cells. Recent findings further suggest that Sb may serve as a potential adjuvant therapy for brain disorders by modulating the gut-brain axis (GBA) to attenuate neuroinflammation. With continued multidisciplinary research, Sb is well-positioned to advance the biotherapeutic landscape. This review aims to synthesize recent advances in the genetics and probiotic mechanisms of Sb, with particular emphasis on its modulatory effects on the GBA.