There are two types of fermentation: alcoholic and lactic acid. Alcoholic fermentation, or ethanol fermentation, is the process in which pyruvate (from glucose metabolism) is broken down into carbon dioxide and ethanol by bacteria and yeast. Alcohol fermentation is used to produce beer, bread and wine. Pyruvate molecules from glucose glycolysis may be further fermented into lactic acid. Lactic acid fermentation converts lactose into lactic acid.