 It also occurs in some kinds of bacteria (such as lactobacilli) and some fungi.It is the type of bacteria that convert lactose into lactic acid in yogurt, giving it its sour taste.These lactic acid bacteria can carry out either homolactic fermentation, where the end-product is mostly lactic acid, or "heterolactic fermentation", where some lactate is further metabolized to ethanol and carbon dioxide (via the phosphoketolase pathway), acetate, or other metabolic products, e.g.