Trader Joe's website that explains the three kinds of rennet, which are animal, vegetable, and microbial, the latter two of which are acceptable for lacto-vegetarians. Separation, or coagulation, of the milk requires two stages. First, bacterial cultures and enzymes are added to reduce the pH and prepare the milk for the addition of rennet.
Rennet is added after cultures and enzymes are used.
Rennet is the dried commercial extract of rennin, the enzyme that is responsible for most of the milk coagulation that takes place. Traditionally, rennet is derived from animals. However, some vegetable juices and extracts are used as rennin, and modern advances in science have enabled micro-organisms to produce enzymes that mimic animal rennet. All three types are found in Trader Joe's cheeses. This is a less common form of rennet, due to its expense, but some cheeses are traditionally made from this type of rennet.