Catalytic activities of fungal oxidases in hydrophobic ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate-based microemulsion

For hydrophobic ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]), an H2O-in-[BMIM][PF6] microemulsion could be formed in the presence of nonionic surfactant Triton X-100 (TX-100). In such a medium, both lignin peroxidase (LiP) and laccase could express their catalytic activity with the optimum molar ratio of H2O to TX-100 at 8.0 for LiP and >20 for laccase, and the optimum pH values at 3.2 for LiP and 4.2 for laccase, respectively. As compared with pure or water saturated [BMIM][PF6], in which the two oxidases had negligible catalytic activity due to the strong inactivating effect of [BMIM][PF6] on both enzymes, the use of the [BMIM][PF6]-based microemulsion had some advantages. Not only the catalytic activities of both fungal oxidases greatly enhanced, but also the apparent viscosity of the medium decreased.