A novel water-in-ionic liquid microemulsion and its interfacial effect on the activity of laccase

It is of great significance to develop an appropriate water-in-ionic liquid (W/IL) microemulsion suitable for the expression of the catalytic activity of a given enzyme. In this paper, the phase diagram of a new AOT/Triton X-100/H2O/[Bmim][PF6] pseudo ternary system is presented. With the aid of nonionic surfactant Triton X-100, AOT could be dissolved in hydrophobic ionic liquid [Bmim][PF6], forming a large single phase microemulsion region. The water-in-[Bmim][PF6] (W/IL) microemulsion domain was identified electrochemically by using K3Fe(CN)6 as a probe. The existence of W/IL microemulsions was demonstrated spectrophotometrically by using CoCl2 as a probe. New evidences from the FTIR spectroscopic study, which was first introduced to the W/IL microemulsion by substituting D2O for H2O to eliminate the spectral interference, demonstrated that there existed bulk water at larger ω0 values (ω0 was defined as the molar ratio of water to the total surfactant) in the W/IL microemulsion, which had remained unclear before. In addition to the inorganic salts, biomacromolecule laccase could be solubilized in the W/IL microemulsion. The laccase hosted in the microemulsion exhibited a catalytic activity and the activity could be regulated by the composition of the interfacial membrane.