Partial purification and characterization of extracellular protease from a halophilic and thermotolerant strain Streptomyces pseudogrisiolus NRC-15.

An alkaline protease was purified from a halophilic and thermotolerant potent alkaline protease-producing strain Streptomyces pseudogrisiolus NRC-15 using ammonium sulphate precipitation and Sephadex G-100 column chromatography. The enzyme was purified to 77.24-folds with a yield of 91.8% and the specific activity was 112 U/mg of protein. The protease showed a single band on SDS-PAGE with its molecular mass at 20 kDa and exhibited a maximum relative activity of 100% using casein as a substrate and. The enzyme had an optimum pH of 9.5 and displayed optimum activity at 50°C. The enzyme activity was completely inhibited by the serine protease inhibitor PMSF, suggesting the presence of serine residue in the active site. The enzyme activity was increased by the metal ions Ca2+, Co2+, K+ and Mg2+. The enzyme significantly enhanced the removal of stains when used with wheel detergent, indicating the potential of the enzyme for using as a laundry detergent additive to improve the performance of heavy-duty laundry detergent.