The characteristic flavour and aroma of any beer is, in large part, determined by the yeast strain employed and the wort composition. In addition, properties such as flocculation, wort fermentation ability (including the uptake of wort sugars, amino acids, and peptides), ethanol and osmotic pressure tolerance together with oxygen requirements have a critical impact on fermentation performance. Yeast management between fermentations is also a critical brewing parameter. Brewer’s yeasts are mostly part of the genus Saccharomyces
. Ale yeasts belong to the species Saccharomyces cerevisiae
and lager yeasts to the species Saccharomyces pastorianus
. The latter is an interspecies hybrid between S. cerevisiae
and Saccharomyces eubayanus.
Brewer’s yeast strains are facultative anaerobes—they are able to grow in the presence or absence of oxygen and this ability supports their property as an important industrial microorganism. This article covers important aspects of Saccharomyces
molecular biology, physiology, and metabolism that is involved in wort fermentation and beer production.
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