African catfish (Clarias gariepinus) visceral protease: its specific activity and molecular weight at different purification stages

Abstract

The fish consumption has increased tremendously due to the dramatic increase in world population. Catfish, the most cultivated species worldwide, showed an increasing trend in global production from year to year. Hence, loads of fish by-products (FBP) were generated especially viscera, materials rich in digestive enzyme notably protease. FBP is often thrown away without any attempt of recovery leading to serious environmental pollution and disposal problems. However, the application of certain protease in either food or non-food industry has become a controversial issue with regards to religious belief (porcine-related product or unslaughtered animals without religious compliance) and health concerns (Bovine Spongiform Encephalopathy (BSE) diseases). Therefore, in this study, protease was extracted and purified from the visceral waste of African catfish (Clarias gariepinus). This study aimed to identify the specific activity and molecular weight of the purified protease at different purification stages. The crude protease was extracted and purified using 60% ammonium sulfate precipitation and dialysis. The study showed that the fresh viscera contained 5.9% protein. The specific activity of the protease indicated a gradual increase as it was further purified up to the dialysis stage (608.70 U/ mg) from the crude extract (263.82 U/mg) by 2.3 folds with half of the visceral protease managed to be recovered (61.43%). In SDS PAGE analysis, purified protease from the dialysis process portrayed unique features such as dimer with an apparent low molecular weight of 15 kDa and 16 kDa. It was obvious that the utilization of the visceral waste from a halal source such as catfish for the extraction of a beneficial protease would be a winwin situation in both environment and industry players from all sectors.