Saccharomyces cerevisiae

Genus/species (aliases): Saccharomyces cerevisiae (Candida robusta, anamorph, Cryptococcus fermentans, Saccharomyces (several species), Torula cerevisiae, Torulopsis fermentans, Torulopsis sexta)

 

Classification (ascomycete/basidiomycete): Ascomycete, teleomorph

Morphology:

Cell: Reproduce by budding, spherical to ovoid, no or simple pseudohyphae

Colony:

  • Malt agar: Medium sized white convex circular
  • WLgreen flat circular colony

Reproduction:

  • Spore: Spherical often in groups of four
  • Zygote: Dumbell-shaped
  • AscusGroup of four spores arranged in a tetrad conformation

Liquid Growth: Dispersed

 

Physiological Traits:

  • Fermentation: Glucose, variable fermentation of: Galactose, Sucrose, Maltose, Trehalose, Melibiose, Raffinose, Melezitose, Starch.
  • Assimilation of: Galactose, Sucrose, Maltose, Trehalose, Melibiose, Raffinose, Melezitose, Starch, Glycerol, Lactate, Ethanol; No assimilation of nitrate or nitrite; no use of ethylamine, lysine or cadaverine as sole N source; variable growth in vitamin-free medium, most strains require biotin and/or thiamin.
  • Growth 37, 40, 42 C: variable
  • Growth Sensitivities: variable resistance to high glucose and NaCl; sensitive to cycloheximide
  • Chromosome bands: 16
  • Glucose is the primary substrate and in anaerobic environments the end products are carbon dioxide, ethanol and heat.

Ecological Traits:

S. cerevisiae is found in nature associated with man and, more rarely, found on the skins of grapes.

Distinguishing Features:

S. cerevisiae was the first yeast to have its entire genome sequenced. This makes it possible to positively identify the organism by genetic analysis. Other traits such as its inability to utilize lysine as a nitrogen source and a high tolerance to SO2and ethanol can be used to differentiate between S. cerevisiae and other yeasts.

Role in wine:

S. cerevisiae is the most common yeast used to carry out alcoholic fermentations in wine production. It is generally part of normal grape, fermentation and winery flora. 

Sensitivities: 

  • SO2:
  • Sorbate­­­­­: Yes
  • DMDC: Yes
  • pH:
  • Acids:
  • Ethanol:
  • Anaerobiosis:
  • Heat: Yes

References:

H. Konig et al. (eds.), Biology of Microorganisms on Grape, in Must and in Wine, Springer-Verlag Berlin Heidelberg 2009, pg. 47-56