PRODUCTION AND CHARACTERIZATION OF AN EXTRACELLULAR THERMOSTABLE LIPASE FROM A THERMOPHILIC BACILLUS SP

The objective of this study was to isolate and characterize thermostable microbial lipases. An enrichment culture technique was used to enrich for thermophiles capable of utilizing olive oil as a carbon source. Out of 44 initial isolates, strain H1, which exhibits the highest lipase activity, was chosen for further characterization. Strain Hf was a spore forming rod, capable of growing at 65 degrees C and was assigned as a Bacillus sp. Optimal lipase production was on medium containing 1% Tween 80. Lipase H1 was partially purified by acetone precipitation, anion exchange chromatography and gelfiltration. The enzyme has a molecular weight of 20,000 (based on gel filtration) and is most active at pH 7.0 at 70 degrees C with a half-life of 50h at 60 degrees C. Lipase H1 had no apparent requirement for cofactors and its activity was completely inhibited in the presence of 1 mM HgCl2. The best substrates for the enzyme were short-chain fatty acid esters. With beta-naphthyl caprylate as a substrate, the enzyme has a K-m of 0.02 mM.