Bioconversions in a water-in-CO₂ microemulsion

In a previous communication (Langmuir 1907, 13, 6080 6984) we reported stabilization of water-in* CO₂ (w/c) micromulsions by fluorinated dichained sulfosuccinate surfactant 'di-HCF4'. In this paper we present a study of enzyme-catalyzed reactions affected in this w/c microemulsion in which the enzyme is located within the dispersed water droplets. Two reactions, a lipase-catalyzed hydrolysis of p-nitrophenol butyrate and lipoxygenase-catalyzed peroxidation of linoleic acid were examined. The activity of both the enzymes in the w/c microemulsion enviroament were essentially equivalent to that in a water-in-heptane microemulsion stabilized by Aerosol OT, a surfactant with the same headgroup as di-HCF4. The inherent condition of low pH of the water droplets in the w/c microemolsion was improved using the buffer MES [2-(N-morpholino)ethanesulfonic acid] which was show to fix the pH in the range 5-6 depending on buffer concentration, pressure, and temperature.