Baker's yeast is the common name for the strains of yeast commonly use as a leavening agent in baking bread and related products, where it converts the fermentable sugars present in the dough into carbon dioxide and ethanol. The use of potatoes, water from potato boiling, eggs, or sugar in a bread dough accelerates the growth of yeasts. Salt and fats such as butter slow down yeast growth. The majority of the yeast used in baking is Saccharomyces cerevisiae, the same species commonly used in alcoholic fermentation. Additionally, Saccharomyces exiguus (also known as S. minor) is a wild yeast found on plants, fruits, and grains that is occasionally used for baking; it is not, however, generally used in a pure form, but comes from being propagated in a sourdough starter.