Abstract
Digestive alkaline proteinases from golden grey mullet (Liza aurata) were extracted and characterized. The crude alkaline protease showed optimum activity at pH 8.0 and 60 degrees C, and it was highly stable over a wide range of pH from 4.0 to 10.0, retaining more than 80% activity after incubation for 1 h at 4 degrees C. The alkaline proteases showed extreme stability toward nonionic and anionic surfactants after preincubation for 1 h at 25 degrees C and relative stability toward oxidizing agents. Additionally, the crude enzyme showed excellent stability and compatibility with various solid and liquid detergents. Further, proteases from golden grey mullet viscera were found to be effective in the deproteinization of shrimp wastes. The protein removal after 3 h at 45 degrees C with an enzyme/substrate (E/S) ratio of 10 U/mg protein was about 76%. The golden grey mullet proteases were also shown to be efficient in the production of antioxidant protein hydrolysate.