Immobilization of lipase on amino-cyclodextrin functionalized carbon nanotubes for enzymatic catalysis at the ionic liquid–organic solvent interface

Amino-cyclodextrin was covalently attached to multiwalled carbon nanotubes (MWNTs). The functionalized MWNTs have a good dispersibility in water. The lipase was adsorbed onto the functionalized MWNTs. The immobilized lipase was utilized for the resolution of the model compound (R, S)-1-phenyl ethanol in heptane, the ionic liquid [Bmim]PF6 as well as the heptane/[Bmim]PF6 mixture. In the reaction media, the enzymatic activity of the immobilized lipase is much higher than that of the native lipase. In comparison to the catalysis in the ionic liquid and heptane, when using the mixture of heptane/[Bmim]PF6 as the reaction medium, the catalysis by the immobilized lipase at the heptane–ionic liquid interface exhibited a higher catalysis activity. This is due to two aspects: the continuous diffusion of substrate from the heptane phase to the ionic liquid phase; the simultaneous extraction of product from the ionic liquid phase. In addition, the interfacial enzymatic catalysis facilitates the reuse of the immobilized lipase and the ionic liquid.