Enzyme encapsulation in microparticles composed of polymerized ionic liquids for highly active and reusable biocatalysts

Horseradish peroxidase (HRP) is encapsulated in polymerized ionic liquid microparticles (pIL-MP), which are prepared by polymerization of 1-vinyl-3-ethylimidazolium bromide in the presence of the crosslinker N,N′-methylenebis(acrylamide) in a concentrated water-in-oil (W/O) emulsion. pIL-MP encapsulating HRP chemically-modified with comb-shaped polyethylene glycol (PM₁₃-HRP) exhibit excellent activity for guaiacol oxidation in an aqueous solution. The PM₁₃-HRP in pIL-MP shows more than 2-fold higher activity than that of the enzyme encapsulated in a polyacrylamide microparticle. The catalytic activity declines with an increase in the crosslinker concentration of the pIL-MP, probably due to suppression of substrate diffusion. The activity of PM₁₃-HRP in pIL-MP depends on the external environment of the gel (i.e. pH and temperature). The pIL-MP are easily recovered from the reaction mixture by centrifugation, which makes it possible to recycle the biocatalyst for repeated oxidation reactions.