Answer:
b. exoenzymes.
Step-by-step explanation:
Casein (Phosphoprotein) is found in milk of mammals like comprises 80% of cow milk. Some bacteria possess the ability to breakdown the casein they produce the clear zone around the growth area of the bacteria in the medium while other bacteria produce the opaque and white.
Casease is the enzyme that breakdown the casein by its proteolytic activity into some bacteria. It convert the casein protein into smaller polypeptides and amino acids.
Casease is an exoenzyme because it is secreted by the bacterial cell into environment and works outside the bacterial cell. While endoenzymes are those that works inside the cell.