Ferments

Ferments are microorganisms, such as yeasts and bacteria, that carry out fermentation, a family of metabolic processes that convert sugars into other compounds with release of energy, usually in the absence of oxygen. Fermentation serves to regenerate NAD+ so glycolysis can continue under anaerobic conditions. The term can also refer to the enzymes that catalyze these reactions or, more generally, to the fermentation process itself.

Two well-known ferments are yeasts, which perform alcoholic fermentation to convert glucose into ethanol and carbon dioxide, and lactic acid bacteria, which produce lactic acid. Other fermentations yield acetic, propionic, or butyric acids, gases, or aroma compounds. Fermentations are described as homofermentative (primarily one end product) or heterofermentative (multiple products).

Fermentation has broad applications in food and beverage production, including bread, beer, wine, yogurt, sauerkraut, kimchi, miso, and tempeh, as well as in industrial biotechnology for producing antibiotics, amino acids, enzymes, organic acids, and biofuels. Conditions such as temperature, pH, oxygen level, and nutrient availability influence the organisms involved and the products formed. The study of ferments spans historical developments, notably Pasteur's experiments, to modern industrial processes and food safety considerations.