Casein Hydrolysis Test

Purpose:  To determine if an organism can produce the exoenzyme casesase.

Principle:  Casease is an exoenzyme that is produced by some bacteria in order to degrade casein. Casein is a large protein that is responsible for the white color of milk. This test is conducted on milk agar which is a complex media containing casien, peptone and beef extract. If an organism can produce casein, then there will be a zone of clearing around the bacterial growth.

The picture to the right illustrates two different casease positive organisms (A and B) and a casease negative organism (C).

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