This genetically modified / GM Kluyveromyces lactis yeast produces chymosin, an enzyme which coagulates milk to form into cheese.
The DNA for this chymosin producing yeast was originally isolated from a calfs stomach lining and inserted into Kluyveromyces lactis yeast. Identical chymosin was then produced by the yeast. This or other similar enzymes are used to create vegetarian cheese. The cheese itself is not labelled as genetically modified product as it does not include the yeast, and is not made using the yeast – it is a created by utilising the product from the yeast. The cheese itself is labeled as vegetarian or vegan if using non-dairy milk.