초록
The aim of this study was to purify and characterize the lipase produced by Burkholderia sp. EQ3, a bacterium isolated from the wastewater pond of a canned fish factory. The lipase was purified to homogeneity with a 70-fold increase in its activity by chilled acetone precipitation, Q-Sepharose Fast Flow and Sephadex G-50 column chromatography, respectively. The molecular mass of the purified lipase was 30.7kDa. The purified lipase showed optimal activity at pH 7.0-7.5 and 30<SUP>o</SUP>C. The enzyme was stable over the pH range of 5.0-8.0 and temperatures between 30 and 55<SUP>o</SUP>C for 1h. Its half-life was 2h at 55<SUP>o</SUP>C. The lipase activity was enhanced in the presence of Ca<SUP>2+</SUP>, Mg<SUP>2+</SUP> and K<SUP>+</SUP> while it was inactivated by Cu<SUP>2+</SUP>, Fe<SUP>2+</SUP> and Zn<SUP>2+</SUP>. It hydrolyzed the natural triglycerides with its highest activity on coconut oil (120%), olive oil (101%) and palm olein (100%). Gum arabic (1%) significantly increased the lipase activity whereas 1.0mM phenyl methyl sulphonyl fluoride strongly reduced the activity. The purified lipase EQ3 retained 80% activity in iso-propanol, but was inactivated by ethanol and iso-octane as well as other hydrophobic solvents. The lipase EQ3 was immobilized by adsorption with Accurel MP-100 and used for wax esters synthesis and compared with five commercial immobilized lipases (Lipozyme RM IM, Lipozyme TL IM, Novozyme 435, Lipase PS and Lipase AK). The transesterification reaction was carried out between coconut oil, palm olein and jatropha oil with oleyl alcohol by using 1U of enzyme, a substrate molar ratio of oil and oleyl alcohol of 1:3 in hexane at 37<SUP>o</SUP>C and 150rpm for 72h. The immobilized lipase EQ3 was most efficient in the synthesis of wax esters with 60.3, 49.6 and 50.1% wax esters from coconut oil, palm olein and jatropha oil, respectively. For the five commercial immobilized lipases, Lipozyme RM IM exhibited the highest wax esters synthesis with 49.2, 41.4 and 48.1% wax esters, respectively.