Chakree Thongraung

Organic Solvent and Laundry Detergent Stable Crude Protease from Nile Tilapia (Oreochromis niloticus) Viscera

The objective of this study was to explore the characteristic activity of crude protease extracted from Nile tilapia viscera. The optimal temperature and pH of the crude protease from Nile tilapia viscera were 60°C and 8.0, respectively. The enzyme was stable to heat treatment up to 45°C and over a pH range of 7–11 for 30–120 min. The protease was effectively inhibited by phenylmethylsulfonyl fluoride (PMSF) and soybean trypsin inhibitor (SBTI). It was activated by Ca2+ and Fe2+, while inhibited in order by Hg2+ > Fe3+ > Cu2+ > Mn2+. The protease showed great stability toward Tween 20, Tween 80, and Triton X-100 and moderate stability toward sodium dodecyl sulfate (SDS) and hydrogen peroxide (H2O2). Nevertheless, it showed excellent stability and compatibility with various solid and liquid laundry detergents at temperatures from 30 to 50°C. The protease showed not only an improved activity but also a satisfied stability in 25% (v/v) organic solvents for 7 days at 37°C. At higher concentrations (50–75%), the protease activity was decreased by hydrophilic solvents, except dimethyl sulfoxide (DMSO), whereas it was enhanced by hydrophobic solvents. Thus, the crude protease is an excellent candidate as a biocatalyst for detergents, foods, pharmaceuticals, and environmental applications.