This is a less common form of rennet, due to its expense, but some cheeses are traditionally made from this type of rennet. This type of rennet is acceptable to loacto-vegetarians. This is a common and less expensive rennet, made from micro-organisms through a process of fermentation. Common micro-organisms include fungi and bacteria. This type of rennet is also acceptable to lacto-vegetarians.
Milk is coagulated by the addition of rennet.
The usual source of rennet is the stomach of slaughtered newly born calves. Vegetarian cheeses are manufactured using rennet from either fungal or bacterial sources. Advances in genetic engineering processes means they may now also be made using chymosin produced by genetically altered micro-organisms. The exact processes in the making of cheese varies between different varieties. However, all cheeses are made by essentially the same method.