Novel approach for the synthesis of ethyl isovalerate using surfactant coated Candida rugosa lipase immobilized in microemulsion based organogels

In our study Candida rugosa lipase coated with various surfactants viz. AOT, CTAB, and Tween 80 was immobilized in microemulsion based organogels (MBGs) and investigated for the production of ethyl isovalerate, a fruity flavor ester. Combinations of different surfactant coated lipase and the surfactant used for preparation of MBG were tried for esterification activity. Amongst various combinations used, CTAB coated lipase immobilized in AOT based MBGs exhibited maximum ethyl isovalerate synthesis (0.082 mol/L) in 9 days. The CTAB coated lipase immobilized in AOT based organogel showed eight-fold increase in the esterification activity as compared to the native lipase. We also found that, increase in the concentration of the CTAB led to the decrease in the catalytic activity of lipase immobilized in AOT based organogels. The AOT based organogels containing CTAB coated lipase could be reused five times, without significant loss in esterification activity. However, after fifth cycle the esterification activity decreased to 40% of the initial activity. The activation energy for catalytic activity of the untreated and surfactant coated lipase was found to be 29.8 and 9.15 kJ, respectively, which depicts some structural change in surfactant coated lipase. Thus, the surfactant coated lipase immobilized in MBGs exhibited significantly higher stability and activity in comparison to uncoated lipase immobilized in MBGs. This strategy seems to hold a good promise for the synthetic flavor industry.