Lactic acid fermentation
Lactic acid fermentation is how glucose or other monosaccharide sugars are converted into lactic acid and energy. There may also be other by-products of this fermentation. It also works with other sugars, such as  sucrose or lactose. Lactic acid bacteria use fermentation to get energy. Fungi, plants and animals will also use this it, if there is a lack of oxygen. As an example, it occurs in  muscle cells. With humans, it occurs if there's too little oxygen in the blood, known as Hypoxemia.