Purification and characterization of a Pseudomonas sp. lipase and its properties in non-aqueous media

An extracellular lipase from Pseudomonas sp. was purified to homogeneity by extraction, Bio-gel P-10 chromatography and Superose 12B chromatography, and a 37-fold purification was attained. The purified enzyme showed a single band when it was subjected to SDS/PAGE and isoelectric focusing. The SDS/PAGE electrophoresis indicated a molecular mass of 30 kDa for this lipase. Its isoelectric point was 4.5. The optimum pH and temperature for hydrolysis were 7.0-9.0 and 45-60°C, respectively. The enzyme was stable between pHs 6 and 12 and below 60°C. In the presence of Ca2+ and Bi3+, the lipase activity was dramatically enhanced by 250% and 154%, respectively. Fe3+, Fe2+, Al3+, Zn2+ and Mn2+ could inhibit this lipase, but Ag+ and Pb2+ showed no influence on hydrolysis activity. Properties of purified lipase for lactonization in organic solvent were also determined. The purified lipase displayed the characteristic of 'pH memory' in organic media. This lipase was also thermostable in organic solvent with an optimum temperature range from 45 to 60°C. Salt dramatically affected the lactonization activity of this lipase.