Reaction Processes of Lipid-coated Enzymes in Supercritical Fluids

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Supercritical fluids (scFs) have been attractive as media for enzymatic reactions, as well as other chemical reactions and media for extraction. Because their physical properties can be manipulated by small changes in pressure and temperature, and several of these properties (e.g., density, diffusiveness, and viscosity) are intermediate between those of gas and liquid. The larger diffusiveness in scF compared to a liquid can be expected to increase the reaction rate.In this report, we report the high catalytic activity of a lipid-coated b-galactosidase for transgalactosylation to alcohols in supercritical fluorofolm (scCHF3). Typical results are stummarized in the figure. A lipid-coated b-galactosidase can catalyse the transgalactosylation from p-nitrophenyl galactopyranoside to 5-phenylpentanol in sufficient efficiency in organic solvents, however the enzyme easily denatured and both the initial rate νo and the conversion decreased drastically in polar solvents above chloroform (the left figure). On the contrary, in the supercritical CHF3, the νo of the reaction increased 20 times compared with those in organic solvents (the right figure). The νo could be reversibly controlled by changing the pressure of supercritical fluid from 1 to 150 atm, and the conversion was almost constant, This means that the reactivity of a lipid-coated enzyme cam be reversibly controlled without denaturation in supercritical fluid by changing pressure (polarity). This is the first example to control enzyme reactions in supercritical fluids.