Optimal immobilization condition of lipase from candida rugosa on amberlite XAD761 for biodiesel producton

Abstract

Recently, lipase catalyzed transesterification for the production of biodiesel has attracted more attention as it produces higher purity product and enables easy separation from the byproduct, glycerol. Candida rugosa lipase (CRL) is the enzyme mostly used for industries but the cost remains a barrier which can be indirectly solved through the immobilization . There are many available methods for immobilization depending on the nature of enzymes , supports and substrates. In this research, CRL was immobilized on hydrophobic support namely, Amberlite XAD761 by adsorption. 200 mg of crude CRL in 20 mM phosphate, pH 7.5 were mixed with 1 g of Amberlite XAD761 and stirred at 350 rpm for 5 hours. In order to obtain the high efficiency of the immobilization, various optimal conditions were determined. The results were as follows; pH at 6, ionic strength of 20 mM with 3 mg/ml of enzyme loading at 30oC for 3 hours. The activity of the immobilized CRL was 0.62 µmole/min/g-support. When this optimized CRL was used to catalyze the transesterification for the production of biodiesel using palm oil as the substrate at 40°C for 24 hours, the obtained conversion from the HPLC analysis was found to be approximately 35%. Then the optimal conditions for transesterification of the obtained immobilized enzymes for the production of biodiesel were investigated. The results were as follows: 7 steps of addition mode of methanol, 4 to 1 molar ratio of methanol to palm oil, 30% of oil by weight enzyme loading, reaction time of 24 hours at 40°C. The production of biodiesel obtained was increased to approximately 72%. The immobilized lipase was stable and retained 30% relative transesterification activity after two cycles. Overall results indicated that biodiesel could be produced by the Candida rugosa lipase immobilized on Amberlite XAD761.