An organic solvent-stable protease from organic solvent-tolerant Bacillus cereus WQ9-2: purification, biochemical properties, and potential application in peptide synthesis.

An extracellular solvent-stable protease producing bacterium WQ9-2 was isolated and identified taxonomically as Bacillus cereus. The protease from strain WQ9-2 was purified to homogeneity with an estimated molecular mass of 37 kDa. The purified protease showed maximum activity at 50 °C and pH 8.0. The protease may be classified as a metalloprotease since it was strongly inhibited by EDTA and 1,10-phenanthroline. The protease showed extreme activity and stability in the presence of both 50% (v/v) hydrophilic or hydrophobic solvents. The synthesis of the precursor (Cbz-Ala-Phe-NH₂) of a bitter dipeptide could be catalyzed by the protease in the presence of 50% dimethylsulfoxide with the product crystals separating directly. The protease displayed broad catalysis specificity for carboxyl component and different substrate preferences in various solvent media, thus confirming its potential application in peptide synthesis.