Rennin is a
proteolytic (
protein-altering)
enzyme that is used to
curdle milk to make
cheese. It is also known as
chymosin.
Rennin is typically used in the form of rennet, a commercial preparation
taken from the abomasums of young calves, but because the demand for rennin is so great, the cheese industry is increasingly turning to rennin-producing microbes such as Mucor miehei and Mucor pusillus.
From the science dictionary at http://biotech.icmb.utexas.edu/