Biocatalysis in Water-in-Ionic Liquid Microemulsions: A Case Study with Horseradish Peroxidase

• Published in: Langmuir 2009-01, Vol.25 (2), p.977-982
• Main Authors: Moniruzzaman, M, Kamiya, N, Goto, M
• Format: Article
• Language: English
• Subjects: Benzocycloheptenes - chemical synthesis; Benzocycloheptenes - chemistry; Biocatalysis; Catalysis; Chemistry; Colloidal state and disperse state; Dioctyl Sulfosuccinic Acid - chemistry; Emulsions; Emulsions. Microemulsions. Foams; Enzyme Activation; Exact sciences and technology; General and physical chemistry; Hexanols - chemistry; Horseradish Peroxidase - metabolism; Hydrogen Peroxide - chemistry; Hydrogen-Ion Concentration; Imidazoles - chemistry; Interfaces: Adsorption, Reactions, Films, Forces; Ionic Liquids - chemistry; Mesylates - chemistry; Molecular Structure; Oxidation-Reduction; Pyrogallol - chemistry; Surface physical chemistry; Surface-Active Agents - chemistry; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Water - chemistry
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/la803118q

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 [C8mim][Tf2N] (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 °C for 30 h.