Production of biodiesel from transesterification catalyzed by immobilized candida rugosa lipase on amberlite XAD7 HP

Abstract

The production of biodiesel, a renewable energy, can be achieved through the transesterification using lipase as the catalyst. Recently, lipase from yeast, Candida rugosa (CRL) has been revealed as one of the most frequently used enzymes for industrial applications. Nevertheless, the high cost of the enzyme remains the barrier which can be indirectly addressed by the immobilization. In this work, the optimal conditions for the immobilization of CRL on hydrophobic polymeric resin, Amberlite XAD7HP by physical adsorption were obtained. 3 mg/ml of CRL in 20 mM phosphate buffer at pH 6 were immobilized on 1 g of Amberlite XAD7HP and continuously stirred at 20oC for 4 hours. The activity of the immobilized CRL was 1.64 µmole/min/g-support. When this immobilized CRL was used to catalyze the transesterification for the production of biodiesel using palm oil as the substrate at 40oC for 24 hours, the percentages of the obtained product from the analysis by high performance liquid chromatography were found to be approximately 50. Then, the optimal conditions for transesterification catalyzed by the obtained immobilized CRL for the production of biodiesel were later obtained. 3 to 1 mole ratio of methanol to palm oil with 4 steps of addition of methanol were catalyzed with 20% (of oil by weight) of immobilized CRL and continuously stirred at 40oC for 12 hours. The production of biodiesel obtained was found to increase to approximately 74%. The immobilized CRL on Amberlite XAD7HP was stable at 40oC and still retained 45% of relative transesterification activity after three reuses. In addition, to further reduce the cost, the production of biodiesel by continuous packed bed reactor (PBR) was investigated to compare with the batch operation. The conditions were 1 to 1 mole ratio of methanol to palm oil, flow rate 0.2 ml/min, 1 gram of CRL with 1 to 4 ratio weight by weight of amount of immobilized CRL to glass beads at 50°C for 48 hours. The biodiesel yield was obtained at approximately 10%. Overall results suggested that production of biodiesel could be accomplished by transesterification catalyzed by the immobilized CRL on Amberlite XAD7HP.