Alkaline Proteases from Rose Snapper (Lutjanus guttatus): Evaluation of Their Stability to Chemical Denaturants and Potential Application to Hydrolyze Seafood Waste Proteins.

Large quantities of by-products are generated after processing of rose snapper (Lutjanus guttatus), such as viscera, head, tail, skin, and bones, which are considered a potential source of valuable molecules. Therefore, the aim of the present study was the biochemical characterization of alkaline proteases isolated from the intestines of L. guttatus and the evaluation of their stability against different chemical denaturants (salts, surfactants/reducing agents, organic solvents, and commercial detergent formulations). In addition, the efficiency to hydrolyze proteins from rose snapper wastes (head, tail, skin, and muscle trimmings) by Alcalase® and alkaline protease extract (APE) isolated from Lutjanus guttatus intestine was evaluated. The APE exhibited a maximum activity at pH 12 and 45 °C and high stability at pH and temperature ranges from 9 to 12 and 10 to 40 °C, respectively. Assays with specific protease inhibitors indicated that trypsin and chymotrypsin are the main types of proteases in APE. An 80% of the proteolytic activity was retained in the presence of 25% NaCl and was stable in the presence of the reducing agent DTT; however, it lost around 70% of proteolytic activity in the presence of 2-mercaptoethanol. The enzymatic activity of APE was maintained above 60% in methanol, ethanol, and propanol as well as in liquid commercial detergents. Alkaline proteases from rose snapper exhibited higher hydrolytic efficiency, compared to the microbial enzyme Alcalase when protein from L. guttatus wastes were hydrolyzed. According to these results, the integral exploitation of rose snapper could be reached by proper usage of its by-products, creating a baseline to promote circular economy.