Lactic acid fermentation is a biological process in which glucose or other six-carbon sugars are converted into cellular energy and the metabolite lactate. This process occurs when oxygen is scarce, allowing organisms to still produce energy in anaerobic conditions.
Lactic acid fermentation is primarily found in two types of organisms: certain bacteria and muscle cells in animals. In humans and other animals, lactic acid fermentation mainly occurs in the muscles during intense exercise, when the oxygen supply is insufficient for aerobic respiration. During this activity, glucose is broken down to produce ATP, and lactic acid is produced as a byproduct.
In addition to animal muscle cells, lactic acid fermentation is also utilized by various bacteria and yeasts. For instance, lactic acid bacteria are essential in the production of fermented foods such as yogurt, sauerkraut, and kimchi. These bacteria thrive in environments low in oxygen, converting sugars into lactic acid, which acts as a preservative and gives these foods their distinctive tangy flavor.