Editing Yeast (section)

== Nutrition and growth ==
Yeasts are [[chemoorganotroph]]s, as they use [[organic compound]]s as a source of energy and do not require sunlight to grow. Carbon is obtained mostly from [[hexose]] sugars, such as [[glucose]] and [[fructose]], or disaccharides such as [[sucrose]] and [[maltose]]. Some species can metabolize [[pentose]] sugars such as ribose,<ref name="Barnett-1975"/> alcohols, and [[organic acid]]s. Yeast species either require oxygen for aerobic [[cellular respiration]] ([[obligate aerobe]]s) or are anaerobic, but also have aerobic methods of energy production ([[facultative anaerobe]]s). Unlike [[bacteria]], no known yeast species grow only anaerobically ([[obligate anaerobe]]s). Most yeasts grow best in a neutral or slightly acidic pH environment.

Yeasts vary in regard to the temperature range in which they grow best. For example, ''[[Leucosporidium frigidum]]'' grows at {{convert|-2|to|20|C|F}}, ''[[Saccharomyces telluris]]'' at {{convert|5|to|35|C|F}}, and ''[[Candida slooffi]]'' at {{convert|28|to|45|C|F}}.<ref name="Arthur-1976"/> The cells can survive freezing under certain conditions, with viability decreasing over time.

In general, yeasts are grown in the laboratory on solid [[growth medium|growth media]] or in liquid [[broth]]s. Common media used for the cultivation of yeasts include [[potato dextrose agar]] or [[potato dextrose broth]], Wallerstein Laboratories nutrient [[agar]], yeast [[peptone]] [[dextrose]] agar, and yeast mould agar or broth. Home brewers who cultivate yeast frequently use dried [[malt extract]] and agar as a solid growth medium. The [[fungicide]] [[cycloheximide]] is sometimes added to yeast growth media to inhibit the growth of ''[[Saccharomyces]]'' yeasts and select for wild/indigenous yeast species. This will change the yeast process.

The appearance of a white, thready yeast, commonly known as [[kahm]] yeast, is often a byproduct of the lactofermentation (or pickling) of certain vegetables. It is usually the result of exposure to air. Although harmless, it can give pickled vegetables a bad flavor and must be removed regularly during fermentation.<ref name="Kaufmann-2002"/>