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 and expressed in B. subtilis WB600 using the pWB980 expression vector. Protease activity of the recombinant B. subtilis WB600 harboring the plasmid pWB980/aprE reached up to 1020 U/ml, approximately 3-folds higher than the native B. clausii strain. Characterization of the recombinant alkaline protease by SDS-PAGE and zymogram analyses indicated a molecular weight of 31 kDa. DNA sequence analysis and the deduced amino acid sequence revealed 98% homology with the extracellular alkaline serine protease from B. clausii KSM-K16.