Lactic acid fermentation is a type of fermentation where lactic acid is produced. This occurs is some bacteria and some fungi. Lactic acid fermentation breaks down a glucose molecule into two molecules of lactate, which combines with hydrogen ions to form lactic acid.

Lactic acid Fermentation

C₃H₄O₃ + 2H → C₃H₄O₃

The energy released is stored in two ATP molecules and several NADH molecules. However, since there is no oxygen available to run the electron transfer chain, the energy of NADH cannot be transferred to ATP. Like any form of fermentation this process is inferior to cellular respiration in generating energy. Bacteria digest lactose in the milk by lactic acid fermentation producing lactic acid which giving milk that sour taste after a person leaves milk out of for a while. Muscle cells in the human body also ferments, only if it can’t get oxygen, producing lactic acids. If the lactic acid builds up muscle cramps will occur.