lactic acid, a three-carbon organic acid produced by anaerobic respiration. L-lactic acid in muscle and blood is a product of glucose and glycogen metabolism; D-lactic acid is produced by the fermentation of dextrose by a species of micrococcus; a mixture of both D- and L-isomers is found in the stomach, in sour milk, and in certain foods prepared by bacterial fermentation, such as sauerkraut. Also called alpha-hydroxypropionic acid, 2-hydroxypropanoic acid. See also glycolysis.
