Ethyl ester production using an immobilized lipase on CaCO₃ and entrapped in calcium alginate

Abstract

This study investigated the biodiesel production from purified palm oil and palm fatty acids by using free and immobilized lipases as biocatalysts. Three methods of lipase immobilizations were studied: 1) adsorption of lipase onto CaC0₃ (CRLA), 2) entrapment of lipase in Ca-alginate matrix (CRLE) and 3) entrapment of CaC0₃-lipase in Ca-alginate matrix (CRLAE). The hydrolytic activities- were compared with those of the free lipase. The preparation of CRLAE was by using of 5% lipase based on oil weight, mass ratio of enzyme/CaC0₃ at 1:2 and adsorption time of 90 min at 4°C. The condition for the bead formation was by using 1% (w/v) Na-alginate to form the bead with a diameter of 1.7 mm. The optimal temperature for lipase activity was 50°C. The immobilized enzyme in CRLE exhibited the highest activity. The immobilized lipase in CRLAE bead filled with the buffer showed approximately 10 time higher activity than that of the one without the buffer. For the biodiesel production, the optimal conditions were at the molar ratio of ethanol to purified palm oil of 9:1 or at the molar ratio of ethanol to palm fatty acid of 3:1, 5% wt (by oil) lipase, 50°C and 24 h o f reaction time, with the yields of ethyl ester from purified palm oil and palm fatty acid at 83% and 16%, respectively. In addition, the substitute of palm fatty acid as a substrate in the ratio of 30% of palms fatty acid: 70% of palm oil at the addition time of 24 h (the total reaction time of 48 h) yielded approximately 81.2%-84.1% ethyl ester by the free lipase, whereas the biodiesel production by the immobilized lipase in CRLE, CRLA and CRLAE resulted in ethyl ester yields of about 74.2%, 57.6% and 42.7%, respectively. The results from the reuse of the immobilized enzymes revealed the significantly reduction of ethyl ester yield from the 1st run to the 3rd run.