BIOCONVERSIONS IN A WATER-IN-CO2 MICROEMULSION

In a previous communication (Langmuir 1997, 13, 6980-6984) we reported stabilization of water-in-CO2 (wic) microemulsions by fluorinated dic hained sulfosuccinate surfactant 'di-HCF4'. In this paper we present a study of enzyme-catalyzed reactions affected in this w/c microemulsio n 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 examine d. The activity of both the enzymes in the w/c microemulsion environme nt were essentially equivalent to that in a water-in-heptane microemul sion stabilized by Aerosol OT, a surfactant with the same headgroup as di-HCF4. The inherent condition of low pH of the water droplets in th e w/c microemulsion was improved using the buffer MES [2-(N-morpholino )ethanesulfonic acid] which was shown to fix the pH in the range 5-6 d epending on buffer concentration, pressure, and temperature.