Immobilization of Penicillium citrinum lipase on ferromagnetic azide-dacron

Abstract

The immobilization of Penicillium citrinum lipase by covalent bond onto ferromagnetic azide-Dacron showed 73% of specific lipase activity retention with 7.3 mg protein/g support. There was no change in either optimal temperature (37°C) or pH (8.0-8.5) after immobilization. The thermal stability of ferromagnetic azide-Dacron-Penicillium citrinum lipase derivative was significant, retaining 86.8% of lipolytic activity while the soluble enzyme retained only 34.2% after 1 h at 45°C, this represented an improvement of 154% in the thermal stability. This lipase did not show inhibition by isopropanol Both soluble and immobilized Penicillium citrinum lipases showed a kinetic of Michaellis-Menten to hydrolysis of 4-nitrophenyl palmitate of (4NPP) at 37°C and pH 8.0. The values of KM were for soluble enzyme of 233 μM and immobilized derivative of 276 μM. This immobilized derivative showed a good operational stability keeping about 75% of initial activity after its reuse for 5 times. Also, it was stable to storage at 4°C in Tris-HCl buffer pH 7.2 with a half-life of 25 days. Immobilized Penicillium citrinum lipase was able to catalyse the synthesis of triolein using glycerol and olive oil as substrates free of organic solvent, with 80% of conversion after 20 h at 40°C. © 2006 Asian Network for Scientific Information.