Ethyl ester procuction from palm oil/palm fatty acid catalyzed by immobilized candida rugosa lipase

Abstract

Bacterial cellulose (BC) is a promising material to be applied as an enzyme-immobilizing support because of its unique physical and biological properties. In this study, the integration method of adsorption and entrapment was applied for lipase immobilization. Firstly, physical adsorption of soluble C. rugosa (CARL) on freeze dried BC-alginate support was performed. Secondly, the immobilized lipase on the BC-alginate support was entrapped within the matrix of calcium alginate (CARLE). The suitable conditions of the immobilization process were as follows: 10% (w/w) CARL to oil; the diameter of circular freeze dried BC-alginate piece of 1.20 cm with the thickness of 3 mm. Sodium alginate solution at 2% (w/v) was used to form gelling layer with a cross linking agent of 120 mM calcium chloride. The immobilized enzyme was applied to catalyze the reaction for biodiesel production from palm oil/ palm fatty acid with ethanol. In this research, the optimal conditions based on the enzymatic transesterification were at the molar ratio of palm oil to 95% (v/v) ethanol of 1:9, reaction temperature of 45 °C, shaking speed at 250 rpm, reaction time of 36 hours and 3 layers of calcium alginate coated on CARLE (CARLE-3L). The yield of the ester obtained by using free lipase (92.61%) was higher than that of CARLE-3L (82.82%), CARLE-4L (70.60%) and CARLE-2L (66.94%), respectively. However, the immobilized enzyme showed higher thermal, mechanical and acid resistance properties than the free enzyme. Besides, increasing of the entrapped layers with calcium alginate could prevent leaching and protect enzyme against violent conditions. It was found that the method of adding free fatty acid with interval time could be applied to decrease the deactivation of the biocatalyst from the acidity of the free fatty acid.