Never mind, I looked it up.
Rennet"The chief use of rennet is in the making of cheese, junket, and chocolate bars.
[ ... ]
Natural rennet is produced in the inner mucosa of the fourth stomach chamber
(the abomasum) of young ruminants.
[ ... ]
Because of the limited availability of proper stomachs for rennet production,
cheesemakers have always looked for other ways to coagulate the milk. Artificial
coagulants are a useful alternative, especially for cheap or lower-quality cheeses.
[ ... ]
Many plants have coagulating properties.
[ ... ]
Worldwide there is also no industrial production for vegetable rennet. Commercial
so-called vegetable rennets usually contain rennet from the mold
Mucor miehei -
see microbial rennet below.
[ ... ]
The flavour and taste of cheeses produced with microbial rennets tend towards some
bitterness, especially if longer maturation is wanted."