ANSWER

Lactic acid bacteria are commonly present in dairy products which ferment the simple sugars and produce the carbon dioxide gases. They are needed for their use in “starter” cultures and dairy fermentations (Cornell University Milk Quality Improvement Program, 2008).

Reference

Cornell University Milk Quality Improvement Program. (2008). Lactic Acid Bacteria – Homofermentative and Heterofermentative. Ithaca, New York: Cornell University.