The lactic acid produced by a Gram-positive bacterium called Lactococcus lactis is needed in cheese formation, as well as the production of pickled vegetables, and other fermented foodstuffs.
Lactococcus lactis is a Gram-positive bacterium used extensively in the production of buttermilk and cheese, but has also become famous as the first genetically modified organism to be used alive for the treatment of human disease. The lactic acid produced by the bacterium curdles the milk that then separates to form curds, which are used to produce cheese. Other uses that have been reported for this bacterium include the production of pickled vegetables, beer or wine, some breads, and other fermented foodstuffs, such as soymilk kefir, buttermilk, and others. 
