*3.3. Preparation of PSC*

The extraction process of PSC was basically identical to the extraction of ASC except for slightly differences. The tilapia skins were extracted by 0.5 M of acetic acid containing 0.1% (*w*/*v*) pepsin

for 48 h with stirring. Then, the supernatant was dialyzed against 0.02 M of Na2HPO4 for 24 h with solution changed every eight hours before being dialyzed against 0.1 M of acetic acid.
