From "Cheesemaking Made Easy" by Vicki and Robert Carroll, Storey Books,
1996:
"Today, rennet is available as both animal and vegetable derivatives.
Vegetable rennet is an enzyme derived from the mold Mucor miehei, and is
marketed in liquid and tablet form."
We just started making our own cheese using a kit obtained locally. The
kit supplier's web site (http://www.cheesemaking.com/) offers three
kinds of rennet:
vegetable "No animals. We promise!"
animal "Moooooooooooooo"
Bio-engineered "Vegetable rennet for the new millennium"
We use the vegetable rennet. As far as I'm concerned, the
bio-engineered version can wait for another millennium.