Isolation and partial characterization of a thermostable extracellular protease of Bacillus polymyxa B-17

Bacillus polymyxa B-17, a sporeforming psychrotroph produced a thermostable protease. The protease was purified to homogeneity from cell free broth culture by precipitation with ammonium sulfate and gel filtration through Sephadex G-100. The enzyme had a temperature optimum at 50°C and shared significant activity at 70°C. The protease was also active over a wide range of pH, 5.5 to 10.0, and had optimum activity at pH 7.5. It was inhibited by metal chelating agents and has a molecular weight of 30 kDa.