Solvent-stable digestive alkaline proteinases from striped seabream (Lithognathus mormyrus) viscera: characteristics, application in the deproteinization of shrimp waste, and evaluation in laundry commercial detergents.

Alkaline proteases from the viscera of the striped seabream (Lithognathus mormyrus) were extracted and characterized. Interestingly, the crude enzyme was active over a wide range of pH from 6.0 to 11.0, with an optimum pH at the range of 8.0-10.0. In addition, the crude protease was stable over a broad pH range (5.0-12.0). The optimum temperature for enzyme activity was 50 °C. The crude alkaline proteases showed stability towards various surfactants and bleach agents and compatibility with some commercial detergents. It was stable towards several organic solvents and retained more than 50% of its original activity after 30 days of incubation at 30 °C in the presence of 25% (v/v) dimethyl sulfoxide, N,N-dimethylformamide, diethyl ether, and hexane. The crude enzyme extract was also tested for shrimp waste deproteinization in the preparation of chitin. The protein removal with a ratio enzyme/substrate of 10 was about 79%.