Lacticfermentation

Lactic fermentation is a catabolic process by which carbohydrates are converted into lactic acid. It occurs under anaerobic conditions when certain microorganisms, especially lactic acid bacteria, metabolize sugars to lactate while regenerating NAD+ to sustain glycolysis. The most common lactic acid bacteria belong to genera Lactobacillus, Lactococcus, Streptococcus, Leuconostoc and Pediococcus. Some microbes can also produce other organic acids and flavor compounds.

In terms of metabolic pathways, lactic fermentation can be homofermentative or heterofermentative. Homofermentative LAB convert hexose sugars almost exclusively to lactic acid, yielding up to two molecules of ATP per glucose. Heterofermentative LAB generate lactate along with carbon dioxide and either ethanol or acetate and formate, producing a broader range of end products and lower ATP yield.

Under practical conditions the process is used to preserve and ferment foods. By lowering pH through lactic acid accumulation, spoilage organisms are inhibited. Salt concentration, temperature and oxygen availability influence the microbial community and flavor outcomes. Lactic fermentation is central to many foods and beverages.

Common examples are yogurt, kefir and other cultured dairy products; sauerkraut, kimchi, pickles and other fermented vegetables; and sourdough bread, where lactic acid bacteria contribute tangy flavors and enhanced crumb structure alongside yeasts.