LAUSR

Abstract In this study, crude alkaline proteases were recovered from rainbow trout (Oncorhynchus mykiss) viscera and partially purified by use of different saturation of ammonium sulfate. The enzyme exhibited highest yield, purity and activity when precipitated at a saturation of 40–60% compared to other ranges of saturation. Molecular weight for extracted protease was between 8-24 kDa. The protease had caseinolytic activity over a wide range of temperatures (30-55 °C) and pH (4-12). Soybean trypsin inhibitor and trypsin-chymotrypsin inhibitor strongly inhibited the enzyme activity but it was stable in the presence of surfactant, oxidizing reagents and organic solvents. The proteases had serine protease activity but no collagenase activity was detected. The current study showed that partially purified protease from the digestive tract of rainbow trout could be applicable in food and detergent industry because of its good activity over a wide temperature and pH range and its good thermal stability.