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. Graphic Abstract