title: Biocatalysis in water-in-ionic liquid microemulsions: a case study with horseradish peroxidase.
abstract: In this article we report the first results on the enzymatic activity of horseradish peroxidase (HRP) microencapsulated in water-in-ionic liquid (w/IL) microemulsions using pyrogallol as the substrate. Toward this goal, the system used in this study was composed of anionic surfactant AOT (sodium bis(2-ethyl-1-hexyl)sulfosuccinate)/hydrophobic IL [C(8)mim][Tf(2)N] (1-octyl-3-methyl imidazolium bis(trifluoromethylsulfonyl)amide)/water/1-hexanol. In this system, the catalytic activity of HRP was measured as a function of substrate concentrations, W(0) (molar ratio of water to surfactant), pH, and 1-hexanol content. The curve of the activity-W(0) profile was found to be hyperbolic for the new microemulsion. The apparent Michaelis-Menten kinetic parameters (k(cat) and K(m)) were estimated and compared to those obtained from a conventional microemulsion. Apparently, it was found that HRP-catalyzed oxidation of pyrogallol by hydrogen peroxide in IL microemulsuions is much more effective than in a conventional AOT/water/isooctane microemulsion. The stability of HRP solubilized in the newly developed w/IL microemulsions was examined, and it was found that HRP retained almost 70% of its initial activity after incubation at 28 degrees C for 30 h.
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, and Center for Future Chemistry, Kyushu University, 744 Moto-oka, Fukuoka 819-0395, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Moniruzzaman
authors.forename: N
authors.initials: N
authors.lastname: Kamiya
authors.forename: M
authors.initials: M
authors.lastname: Goto
mesh_terms: D001567:Benzocycloheptenes / Q000138:chemical synthesis / Q000737:chemistry; D055162:Biocatalysis; D004143:Dioctyl Sulfosuccinic Acid / Q000737:chemistry; D004655:Emulsions; D004789:Enzyme Activation; D000441:Hexanols / Q000737:chemistry; D006735:Horseradish Peroxidase / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007093:Imidazoles / Q000737:chemistry*; D052578:Ionic Liquids / Q000737:chemistry*; D008698:Mesylates / Q000737:chemistry*; D015394:Molecular Structure; D010084:Oxidation-Reduction; D011748:Pyrogallol / Q000737:chemistry; D013501:Surface-Active Agents / Q000737:chemistry; D014867:Water / Q000737:chemistry*
chemical_list: C535265:1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide; D001567:Benzocycloheptenes; D004655:Emulsions; D000441:Hexanols; D007093:Imidazoles; D052578:Ionic Liquids; D008698:Mesylates; D013501:Surface-Active Agents; D011748:Pyrogallol; D014867:Water; D004143:Dioctyl Sulfosuccinic Acid; C036260:1-hexanol; D006861:Hydrogen Peroxide; D006735:Horseradish Peroxidase; C026133:purpurogallin