<Tr> <Th> Main ingredients </Th> <Td> Milk </Td> </Tr> <Tr> <Td_colspan="2"> Cookbook: Soured milk Media: Soured milk </Td> </Tr> <P> Soured milk is a food product produced by the acidification of milk . Acidification, which gives the milk a tart taste, is achieved either through bacterial fermentation or through the addition of an acid, such as lemon juice or vinegar . The acid causes milk to coagulate and thicken, inhibiting the growth of harmful bacteria and improving the product's shelf life . </P> <P> Soured milk that is produced by bacterial fermentation is more specifically called fermented milk or cultured milk . Traditionally, soured milk was simply fresh milk that was left to ferment and sour by keeping it in a warm place for a day, often near a stove . Modern commercial soured milk may differ from milk that has become sour naturally . </P>

Which one of the following microbes causes acidification and curding of milk