Characterization of a thermostable esterase activity from the moderate thermophile Bacillus licheniformis

A new esterase activity from Bacillus licheniformis was characterized from an Escherichia coil recombinant strain. The protein was a single polypeptid e chain with a molecular mass of 81 kDa. The optimum pH for esterase activi ty was 8-8.5 and it was stable in the range 7-8.5. The optimum temperature for activity was 45 degrees C and the half-life was Ih at 64 degrees C. Max imum activity was observed on p-nitrophenyl caproate with little activity t oward long-chain fatty acid esters. The enzyme had a K-M of 0.52 mM for p-n itrophenyl caproate hydrolysis at pH 8 and 37 degrees C. The enzyme activit y was not affected by either metal ions or sulfydryl reagents. surprisingly , the enzyme was only slightly inhibited by PMSF. These characteristics cla ssified the new enzyme as a thermostable esterase that shared similarities with lipases. The esterase might be useful for biotechnological application s such as ester synthesis.