Improved esterification activity of Candida rugosa lipase in organic solvent by immobilization as Cross-linked enzyme aggregates (CLEAs)

Cross-linked enzyme aggregates (CLEA®s) were prepared from Candida rugosa lipase (CrL) using glutaraldehyde as the cross-linker. The optimum conditions of the immobilization process were determined (precipitant: ethanol, crosslinker concentration: 25 mM, enzyme concentration: 50 mg/ml, crosslinking time: 45 min.). CLEAs were shown to have several advantages compared to the free enzyme. They were more stable at 50 °C and 60 °C and had good reusability; retaining 40% of their initial activity after 15 recycles in aqueous media and remaining constant at that level thereafter, suggesting some initial leaching in water. The CLEAs catalyzed esterification reactions in cyclohexane, affording higher conversions than with the free enzyme, especially when longer fatty acids and alcohols were used as substrates.