Saccharomyces

S. boulardii—Therapeutic Probiotic#

The best-characterized fungal probiotic, with demonstrated efficacy in.

C. difficile infection: reduces recurrence by 50-60% when combined with antibiotics (McFarland 2006 Am J Gastroenterol; Surawicz et al. 2000 Clin Infect Dis); inhibits toxin A/B binding to colonocytes and degrades toxin receptor sites (Castagliuolo et al. 1999 Infect Immun).

Anti-inflammatory effects: secretes anti-inflammatory factors that inhibit NF-kB signaling and reduce IL-8 and TNF-alpha production in intestinal epithelial cells (Sougioultzis et al. 2006 BBRC).

Barrier protection: upregulates tight junction proteins and secretory IgA production (Czerucka et al. 2007 Aliment Pharmacol Ther). Antibiotic-associated diarrhea: reduces incidence by approximately 50% across meta-analyses (Szajewska & Kołodziej 2015 Aliment Pharmacol Ther; Hempel et al.

2012 JAMA).

Multiple sclerosis adjunctive use: evaluated as an adjunctive microbiome-targeted intervention in RCT.^{[1]Motlagh Asghari 2023 — Saccharomyces boulardii probiotic supplementation in multiple sclerosis: 4-month randomized clinical trialKimia Motlagh Asghari, Neda Dolatkhah, Hormoz Ayromlou et al. · 2023Open reference 1 ↓}

Unlike bacterial probiotics, S. boulardii is inherently resistant to all antibacterial antibiotics, making it uniquely suited for co-administration during antibiotic therapy (Czerucka et al. 2007 Aliment Pharmacol Ther).

Produces 54-kDa serine protease that degrades C. difficile toxin A and its intestinal receptor (Castagliuolo et al. 1996 Infect Immun; Castagliuolo et al. 1999 Infect Immun).

Colorectal Cancer Mycobiome#

S. cerevisiae is enriched in the CRC mycobiome in multiple cohorts. Saccharomycetaceae showed significant reductions in CRC in some studies, suggesting context-dependent effects.^{[2]Unveiling the overlooked fungi: the vital of gut fungi in inflammatory bowel disease and colorectal cancerYilin Huang, Yang Wang, Xiaotian Huang et al. · 2024Open reference 2 ↓}

Interacts with bacterial communities: Saccharomyces abundance positively correlated with Bifidobacterium, Roseburia, and Ruminococcus in IBD patients.^{[2]Unveiling the overlooked fungi: the vital of gut fungi in inflammatory bowel disease and colorectal cancerYilin Huang, Yang Wang, Xiaotian Huang et al. · 2024Open reference 2 ↓}

Cardiometabolic Disease#

Saccharomyces enriched in HTN+CKD comorbidity patients; positively associated with IFN-gamma, IL-4, and eGFR.^{[3]Exploring the gut mycobiome: differential composition and clinical associations in hypertension, chronic kidney disease, and their comorbidityJuan Qiu, Longyou Zhao, Yiwen Cheng et al. · 2023Open reference 3 ↓} Present in hypertensive cohorts (8.46% of fungal community in HTN vs lower in normotensive controls).^{[4]Gut mycobiome in cardiometabolic disease progression: current evidence and future directionsXiaoyu Wei, Zixin Guo, Jingyang Wang et al. · 2025Open reference 4 ↓}

S. boulardii supplementation failed to improve cardiac function in the GutHeart trial for heart failure (Awoyemi et al. 2021 eBioMedicine—GutHeart trial).

Crohn's Disease and ASCA#

Anti-Saccharomyces cerevisiae antibodies (ASCA) are a well-established serological marker for Crohn's disease, suggesting immune sensitization to this yeast in the inflamed gut (Main et al. 1988 BMJ; Quinton et al. 1998 Gut).

ASCA positivity distinguishes Crohn's from UC (sensitivity ~55%, specificity ~90%) and is associated with more aggressive disease phenotype including stricturing and penetrating complications (Dubinsky et al. 2006 Inflamm Bowel Dis).

Metal Biosorption#

Saccharomyces species have significant metal biosorption capacity, binding Heavy Metals to cell wall components (mannoproteins, glucans, chitin) (Wang & Chen 2006 Biotechnol Adv).

S. cerevisiae cell walls bind Cadmium, Lead, Copper, Zinc, and Chromium from solution, a property exploited in industrial bioremediation (Wang & Chen 2006 Biotechnol Adv; Machado et al. 2010 J Hazard Mater).

In the gut context, dietary or supplemental yeast may reduce bioavailable metal concentrations, potentially mitigating metal-induced dysbiosis. Zinc-dependent alcohol dehydrogenase and copper (Cu)/zinc (Zn)-superoxide dismutase are key metalloenzymes in Saccharomyces biology.

Key Metabolites#

Ethanol—primary fermentation product of S. cerevisiae; small amounts produced in the gut may affect hepatic metabolism.

Beta-glucans—cell wall polysaccharides that stimulate Dectin-1 immune receptor, upregulating tight junction proteins and modulating macrophage function.^{[2]Unveiling the overlooked fungi: the vital of gut fungi in inflammatory bowel disease and colorectal cancerYilin Huang, Yang Wang, Xiaotian Huang et al. · 2024Open reference 2 ↓}

Proteases—S. boulardii secretes serine proteases that degrade bacterial toxins and pro-inflammatory signaling molecules. Short-chain fatty acids—indirect contribution via cross-kingdom metabolic interactions with SCFA-producing bacteria.