Fermentation

Fermentation is a type of anaerobic metabolism that harnesses the redox potential of the reactants to make adenosine triphosphate (ATP) and organic end products. Organic molecules, such as glucose or other sugars, are catabolized and their electrons are transferred to other organic molecules (cofactors, coenzymes, etc.). The transfer to organic molecules distinguishes fermentation from cellular respiration which concerns the transfer to oxygen (aerobic) or other inorganic (anaerobic) molecules. Anaerobic glycolysis is a related term used to describe the occurrence of fermentation in organisms (usually multicellular organisms such as animals) when aerobic respiration cannot keep up with the ATP demand, due to insufficient oxygen supply or anaerobic conditions.

Fermentation is important in several areas of human society. Humans have used fermentation in the production and preservation of food for 13,000 years. It has been associated with health benefits, unique flavor profiles, and making products have better texture. Humans and their livestock also benefit from fermentation from the microbes in the gut that release end products that are subsequently used by the host for energy. Perhaps the most commonly known use for fermentation is at an industrial level to produce commodity chemicals, such as ethanol and lactate. Ethanol is used in a variety of alcoholic beverages (beers, wine, and spirits) while lactate can be neutralized to lactic acid and be used for food preservation, as a curing agent, or as a flavoring agent.

This complex metabolism utilizes a wide variety of substrates and can form nearly 300 different combinations of end products. Fermentation occurs in both prokaryotes and eukaryotes. The discovery of new end products and new fermentative organisms suggests that fermentation is more diverse than what has been studied.