The species is able to ferment hexose sugars, such asDglucose, D-fructose, and D-mannose. The rate of D-glucose
fermentation is normally the most aggressive. Other sugars that
can be fermented by most strains of S. cerevisiae include
sucrose, maltose, maltotriose, and D-galactose, whereas
dextrins and starch are fermented only by specialized varieties
ofS. cerevisiae(Saccharomyces diastaticus), and lactose is not
fermented by this species. TheL-sugars and all pentoses also are
considered nonfermentable, although xylulose can be fermented. Aside from the hexoses and their dimers and oligomers, the species readily metabolizes nonfermentable
compounds, such as lactic acid, other organic acids, and
polyhydroxy alcohols. Strains ofS. cerevisiae differ in their
ability to utilize nitrogen sources (see Saccharomyces: Brewer’s
Yeast). Many inorganic ammonium salts have been found to
promote growth, whereas strains exhibit different abilities to
utilize free amino acids. Nitrates as well asL-amino acids such
as L-proline usually are not utilized. Conversely, some
S. cerevisiaestrains can utilize urea as a source of nitrogen
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