Lipase from <i style="">Pseudomonas aeruginosa</i> MTCC 2488: Partial purification, characterization and calcium dependent thermostability

Abstract

<i style="">Psuedomonas aeruginosa</i> MTCC 2488 produced lipase on Rhodamine B agar plates containing olive oil. Extra-cellular lipase activity was analyzed spectrophotometrically using Tween-20 as well as olive oil as substrate. The semipurified enzyme, precipitated by 30% saturated ammonium sulphate, showed 20.79 fold increase in specific activity (U/mg) and reduction in carbohydrate content to 1.7% as compared to the crude enzyme. The enzyme hydrolyzed Tween-20 and -40 better than Tween-60 and -80. Lipase has been found to be thermostable with maximum activity at 55-60^oC but marked decrease was observed above this temperature. Ca²⁺ seemed to play an important role in the thermostability as 97% of enzyme activity was retained after 2 hr incubation at 65^oC and 1hr incubation at 70^oC in presence of 10 m<i style="">M</i> CaCl₂. However, thermostability of the enzyme was decreased considerably in presence of 5 m<i style="">M</i> EDTA, confirming the enzyme to be a metalloprotein. Lipase has been found to be stable in presence of 30% acetone, methanol and ethanol. While, the enzyme activity was decreased by 30-50% in presence of n propanol, 2 propanol, n methyl propanol, isooctane and hexane. Further, 30% butanol resulted in ~65% decrease in the enzyme activity. Lipase has been found to be stable in presence of nonionic detergents, whereas anionic detergent, SDS completely inactivated the enzyme.