Cloning and enhanced expression of an extracellular alkaline protease from a soil isolate of Bacillus clausii in Bacillus subtilis

Alkaline proteases are of industrial importance, mainly in the detergent industry. In this study, the extracellular alkaline serine protease gene, aprE, from Bacillus clausii was amplified by PCR and further cloned into B. subtilis WB600 using the pWB980 expression vector. Measurement of protease activity in the recombinant B. subtilis WB600 harboring the pWB980-aprE showed a yield of 1020 enzyme units ml-1, approximately 3 folds higher than the native B. clausii. Characterization of the alkaline protease by SDS-PAGE and zymogram analyses indicated a molecular weight of 31 kDa for the cloned enzyme with biological activity. DNA sequence analysis and the deduced amino acid sequence revealed 98% homology with the extracellular alkaline serine protease from Bacillus clausii KSM-K16.