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.