Ethanol fermentation

Ethanol fermentation is a fermentation process that converts sugar into cellular energy, producing ethanol, and carbon dioxide. Because ethanol is an alcohol, it is also known as alcoholic fermentation. Yeast will do this without using oxygen, the process is anaerobic. It also happens in some kind of fish, where it produces energy, when there is little oxygen. 
Ethanol fermentation has many uses, including the production of alcoholic drinks (such as beer or wine), the production of ethanol fuel, and the cooking of bread.