Cloning and Characterization of a Bacterial Cell-Bound Type B Carboxylesterase from Bacillus sp. BP-7

A clone producing halos on tributyrin plates was isolated from a genomic library of Bacillus sp. BP-7. The insert contained an open reading frame that coded for a protein of 487 amino acids with homology to carboxylesterases. The cloned enzyme showed clear preference for esters of short-chain fatty acids, being classified as an esterase. Maximum activity was found at 45 degrees C and pH 7.5. The enzyme displayed stability in the pH range from 6 to 9.5, and at temperatures from 4 degrees to 45 degrees C. Zymogram analysis of the protein revealed a molecular mass of 53 kDa and a pI of 5.1. The enzyme showed homology to members of the bacterial subclass of type B carboxylesterases, a set of proteins potentially useful for biotechnological applications.