Fermentation is the process by which a carbohydrate molecule is broken down into alcohol and carbon dioxide in the absence of oxygen. During this process, two molecules of ATP is produced. In the absence of oxygen, pyruvate formed from glycolysis will undergo fermentation process. During the process of fermentation, NADH from glycolysis will be converted back to NAD+. This is necessary in order for glycolysis to continue. Thus, fermentation regenerate more NAD+ and only a few molecule of ATP.
