A very long name for such a tiny organism. It is a very strong strain that is capable of fermentation or causing bread dough to rise. Yeast cells digest food to obtain energy for growth. The process, alcoholic fermentation, produces useful end products, carbon dioxide and ethyl alcohol, which are released by the yeast cells into the surrounding liquid. This is how alcoholic drinks are produced from starch containing flours, i.e., barley flour for making beer and wheat, corn or other grains for making whiskey.
Fermentation occurs naturally in nature.
For instance, many berries break open in late fall when they are over-ripe and full of sugar. Natural yeast from the air, so tiny they cannot be seen, lodge on the surface of these berries, which then become fermented and alcoholic. In commercial fermentation of grape juice for the production of wine, the carbon dioxide gas escapes from the solution. Evidence of gas can be seen in the heavy foam caps in fermenting wine tanks. In bread baking, when yeast ferments the sugars available from the flour and from added sugar, the carbon dioxide gas cannot escape because the dough is elastic and stretchable.