Chihuil Sea Catfish Bagre panamensis Viscera as a New Source of Serine Proteases: Semi-purification, Biochemical Characterization and Application for Protein Hydrolysates Production

The recovery of proteases from fish viscera could be a strategy to reduce environmental problems caused by inadequate disposal of fish by-products. This study reports the biochemical characterization of proteases isolated from chihuil sea catfish (Bagre panamensis) intestines and the evaluation of their stability to different physical and chemical factors. Protein hydrolysates from chihuil muscle and casein were produced using its semi-purified proteases extract (SPE) and alcalase. Assays with specific protease inhibitors indicate that trypsin and chymotrypsin are the main types of serine proteases in SPE. Semi-purified enzymes exhibited proteolytic activity at alkaline pH (9–12), and high stability at low/mild temperatures (10–40 °C). A 92% of SPE proteolytic activity was retained in the presence of 30% NaCl. The enzyme extract was stable in reducing agents (2-mercaptoethanol and DTT) but lost about 70% of proteolytic activity in anionic detergents like SDS and tween-80. Organic solvents did not affect the enzyme activity of SPE. Finally, maintaining a same E/S ratio for protein hydrolysates elaboration, chihuil serin proteases exhibited a higher hydrolytic efficiency compared to alcalase when casein and proteins from chihuil muscle were hydrolyzed. Thus, the semi-purification of serine proteases from chihuil viscera provided a low-cost source of enzymes with interesting catalytic features.