saccharomyces

Saccharomyces is a genus of yeasts in the phylum Ascomycota. Members are unicellular fungi that reproduce mostly by budding and are known for their role in fermentation. The best known species is Saccharomyces cerevisiae, widely used in baking and brewing, but the genus also includes others such as Saccharomyces boulardii, used as a probiotic, and several wild relatives.

Biology: These yeasts are typically oval, 5–10 micrometers, and occur on sugar-rich substrates. They grow aerobically or fermentatively; under high sugar, they favor fermentation even in the presence of oxygen (Crabtree effect). They reproduce asexually by budding and can form asci with ascospores during meiosis in some life cycle stages. In S. cerevisiae, diploid and haploid life cycles allow genetic exchange via mating and sporulation.

Ecology: In nature, Saccharomyces species are found on the skins of fruits, in nectar, and in environments rich in sugars; they thrive in human-made fermentations, including bread, beer, wine, and spirits. Domesticated strains have been selected for rapid growth, alcohol tolerance, and flavor production.

Uses and significance: S. cerevisiae is the primary yeast in baking and alcoholic fermentation, converting sugars into ethanol and carbon dioxide. It is also a major model organism in molecular and cellular biology, with a fully sequenced genome and numerous genetic tools. S. boulardii is used as a probiotic to support intestinal health.

Safety and health: Generally regarded as safe for food use. In rare cases, Saccharomyces infections can occur in people with weakened immune systems or implanted devices, though such cases are uncommon. Proper handling in food processing and medical contexts minimizes risk.