Abstract: Lipase of Penicillium notatum was purified to electrophoretic homogeneity by ammonium sulphate precipitation, ion-exchange, and hydrophobic interaction chromatography. The purified enzyme displayed a solitary band in the 46-kDa region on sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS–PAGE). The pH and temperature optima were found to be 9.5 and 40 °C, respectively. It showed stability over broad pH range (pH 6.0–12) and higher thermal tolerance with half-lives (t1/2) of 8.25, 3.2, 1.12, and 0.58 h at 40, 50, 60 and 70 °C, respectively. The Kmand Vmaxvalues for p-nitro phenyl palmitate (pNPP) hydrolysis were 3.33 mM and 232.6 µmol/mL min−1, respectively. The energy of activation for denaturation Ea(d)was 81.1 kJ/mol, whereas the entropy (ΔS*), enthalpy (ΔH*) and free energy (ΔG*) of thermal inactivation of lipase were recorded to be −0.083 Jmol−lK−l, 78.48 and 104.54 kJ/mol, respectively, at 40 °C. The enzymatic activity was substantially improved by Ca2+and Mg2+, and suppressed in the presence of Co2+,Cd2+, Pb2+and Fe3+ions to various levels. Exposure to hydrophobic environment did not affect the enzyme stability; however, protease solution deactivated the enzyme. Considering all these properties, this fungal lipase would be an interesting candidate for future organic synthesis application. Graphical Abstract: [Figure not available: see fulltext.]
Bibliographical noteFunding Information:
This work is a part of Ph.D. studies of Ms. Saima Rehman and was financially supported by Higher Education Commission (HEC), Pakistan under the Indigenous Ph.D. 5000 Scholarship Scheme. The authors are thankful to HEC for timely provision of funds.
© 2016, Springer Science+Business Media New York.
- Penicillium notatum