Optimized Selective Media Enhance the Isolation and Characterization of Gut-Derived Probiotic Yeasts

Area of Science:

• Microbiology
• Probiotics Research
• Gut Microbiome Studies

Background:

• Gut-associated yeasts are increasingly recognized for their potential as probiotics.
• Traditional isolation methods can be hindered by bacterial overgrowth.
• Characterizing yeast strains for safety and functionality is crucial for probiotic development.

Purpose of the Study:

• To apply a guided culturomics workflow for isolating and characterizing gut-associated yeasts as probiotic candidates.
• To optimize culture conditions for selective yeast isolation from the gut microbiome.
• To screen isolates for safety, stress tolerance, and functional probiotic properties.

Main Methods:

• Optimized culturomics using Dixon agar and Modified Schädler Agar with a selective antibiotic cocktail and anaerobic incubation at 37°C.
• Isolated 305 yeast strains from three healthy donors, followed by exclusion of Candida and pseudohyphal morphotypes.
• Conducted safety screening (hemolysis, DNase, coagulase), simulated gastrointestinal stress tests (acid, bile), antimicrobial activity assays, and bile salt hydrolase activity assessment.

Main Results:

• Successfully isolated 127 non-Candida yeast strains, with 26 deemed safe after screening.
• Twenty of the 26 safe isolates demonstrated significant survival (>50%) under simulated gastric pH 2.0 or 0.5% bile salt conditions.
• Several isolates exhibited broad-spectrum antimicrobial activity against pathogenic bacteria like Staphylococcus aureus, Escherichia coli O157:H7, and Salmonella species.
• Intracellular bile salt hydrolase activity was observed in all isolates, suggesting potential cholesterol-lowering effects.

Conclusions:

• The guided culturomics workflow effectively minimized bacterial interference and enriched for safe, functional gut-associated yeasts.
• Identified several promising non-Candida yeast strains with robust probiotic potential, including significant antimicrobial and stress-tolerance capabilities.
• These findings support the development of novel yeast-based probiotics for modulating the gut microbiome and promoting gastrointestinal health.