Fermentatsioon

Fermentatsioon is a metabolic process used by microorganisms to convert sugars into other compounds, usually in the absence of oxygen. In fermentation, glycolysis provides pyruvate, and cells regenerate NAD+ by channeling pyruvate to products such as lactic acid, ethanol, or organic acids. This allows continued ATP production when respiration is limited or unavailable.

Major types include lactic acid fermentation, alcoholic fermentation, and acetic fermentation. Lactic acid fermentation, carried out by bacteria such as Lactobacillus and Streptococcus, yields lactic acid and is common in dairy products and fermented vegetables. Alcoholic fermentation, performed by yeasts such as Saccharomyces, produces ethanol and carbon dioxide and underpins beer, wine, and bread making. Acetic fermentation oxidizes ethanol to acetic acid, used in vinegar production. Some bacteria perform mixed acid fermentations, producing a range of organic acids.

Applications span food and beverage production, industrial biotechnology, and preservation. Fermentation creates texture, flavor, and aroma in foods such as bread, yogurt, cheese, sauerkraut, beer, and wine, while also extending shelf life. Industrially, microorganisms are harnessed to produce solvents, organic acids, enzymes, vitamins, antibiotics, and biofuels under controlled conditions with starter cultures.

Historically, fermentation has been used for thousands of years for preserving and transforming foods and drinks. The microbiological basis of fermentation was clarified in the 19th century, notably by Louis Pasteur, contributing to the development of modern industrial microbiology and bioprocessing.