Fermentation is a metabolic process that produces chemical changes in a substrate in the absence of oxygen. The most common substrate for fermentation is glucose, but other carbohydrates such as fructose, galactose, and mannose can also be used. Fermentation is used to produce alcohols, acids, and other chemicals.In fermentation, glucose is converted into pyruvate and then into ethanol and carbon dioxide. The process of fermentation is used to produce beer, wine, and other alcoholic beverages. It is also used in the production of bread, cheese, and other dairy products.The fermentation process is mediated by enzymes that are produced by yeast or bacteria. These enzymes convert the glucose into pyruvate. The pyruvate is then converted into ethanol and carbon dioxide by the enzyme alcohol dehydrogenase.The fermentation process is an important step in the production of food and beverages. It is also used in the production of pharmaceuticals and other chemicals.