Studies on the preparation of water-insoluble derivatives of rennin and chymotrypsin and their use in the hydrolysis of casein and the clotting of milk.

1. Enzymically active insoluble derivatives of chymotrypsin and rennin were prepared by coupling each enzyme to agarose as described by Porath, Axén & Ernback (1967) and rennin to aminoethylcellulose by the method of Habeeb (1967). 2. Agarose-chymotrypsin was stable over the range pH2-9, but agarose-rennin released active enzyme into solution at above pH2 and aminoethylcellulose-rennin was similarly unstable at certain pH values. 3. Each derivative appeared to catalyse the clotting of milk at 30 degrees , but this was probably entirely due to enzyme released into solution from the carrier. 4. The presence of a competitive inhibitor of chymotrypsin during its coupling to agarose had no effect on the activity or stability of the resulting derivative. 5. The characteristics of agarose and cellulose render them not entirely suitable for use in a continuous system with milk.