Production and characterization of an extracellular thermostable lipase from a thermophilic bacillus sp

Abstract

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 HI, which exhibits the highest lipase activity, was chosen for further characterization. Strain HI was a spore forming rod, capable of growing at 65 °C and was assigned as a Bacillus sp. Optimal lipase production was on medium containing 1% Tween 80. Lipase HI was partially purified by acetone precipitation, anion exchange chromatography and gel filtration. The enzyme has a molecular weight of 20,000 (based on gel filtration) and is most active at pH 7.0 at 70°C with a half-life of 50h at 60°C. Lipase HI 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 β-naphthyl caprylate as a substrate, the enzyme has a Kmof 0.02 mM. © 1994, Applied Microbiology, Molecular and Cellular Biosciences Research Foundation. All rights reserved.