Biocatalytic microreactor incorporating HRP anchored on micro-/nano-lithographic patterns for flow oxidation of phenols

A highly durable and versatile micro scale biocatalytic reactor has been designed and investigated in the heterogeneous enzyme-catalytic oxidation of phenols. It consisted of optical or electron beam lithographic gold deposited layer with different thickness from nano- to micro-scale on a semiconductor surface. Horseradish peroxidase (HRP) enzyme was immobilized on the gold-surface using two different approaches (i.e., physical adsorption and self-assembled monolayer). Characterization of those HRP-gold surfaces was made using AFM (atomic force microscopy) coupled with ellipsometry measurements, SEM (scanning electron microscopy), STM (scanning tunneling microscopy) and spectrophotometric technique. The catalytic performances of the developed structures were investigated after their incorporation in microreactors using a recycling-flow system dedicated to phenols oxidation. In order to optimize the efficiency of the oxidation process it was checked the effect of the successively addition of the reagent, the influence of the reaction time, the stability and the reuse of the biocatalytic micro-system. Maximum phenol conversion was of 35.1%. In addition to phenol the system has also been investigated in oxidation of other phenolic compounds such as cathecol, hydroquinone, rezorcine, β-naphtol, o/p-aminophenol and 4-metoxyphenol.