Mixed lipases for efficient enzymatic synthesis of biodiesel from used palm oil and ethanol in a solvent-free system

The enzymatic synthesis of biodiesel from used palm oil and ethanol using immobilized lipases in a solvent-free system was attempted. Five immobilized lipases, Lipase AK from Pseudomonas fluorescens, Lipase PS from Pseudomonas cepacia, Lipase AY from Candida rugosa, Lipozyme TL IM from Thermomyces lanuginosa and Novozym 435 from Candida antarctica, were screened based on their catalytic activities on reactions involved in biodiesel synthesis. The combined use of Lipase AY and Lipase AK gave a higher yield of biodiesel than using Lipase AK alone. The optimal conditions for biodiesel synthesis using mixed lipases in a batch system were: 2% water content, 10% enzyme dosage and 3:1 molar ratio of ethanol to oil. The mixed lipases could be used in 15 replicates with retained relative activity higher than 50%. In a continuous system using mixed lipases packed in packed-bed reactor, >67% of biodiesel was achieved.