(228d) Electric Field Enabled Continuous Oxidation Catalyzed By Laccase

Liwei Ren; Diannan Lu*; Zheng Liu

Key lab of Industrial Biocatalysis, Ministry of Education

Department of Chemical Engineering, Tsinghua University, Beijing 100084, PR China.

E-mailï¼?ludiannan@mail.tsinghua.edu.cn

 ABSTRACT

Laccase is a kind of copper-containing oxidase found in plants and fungi. It is unique capability in catalysing oxidation of phenols using molecular oxygen attracted immense efforts in exploring its applications in textile, papermaking, wastewater treatment and so on. However the poor activity resulted from the lagged electron transfer among the cooper ions in the active site of laccase hinders the above mentioned applications of laccase.

Here we present a method using electric filed to enhance the intramolecular electron transfer of laccase. In the present study, laccase from Trametes versicolor (TvL) was adsorbed on a mesoporous carbon nitride (CN) matrix consisting pyridine and benzene rings interconnected by nitrogen atoms. The immobilized laccase was coated onto Au electrode using PVA as agglutinant, giving rise to a novel CN-Lac/PVA/Au electrode. It is shown that CN-Lac/PVA/Au was highly active for O₂ reduction, requiring an over-potential as low as 0.013 V to generate an current density of 103.1 μA/cm². The structural characterization indicates the protuberances at the CN internal surface acted as molecular wires to connect the active site of laccase and Au electrode.

To test of workability of the CN immobilized laccase in the electric field in the absence of oxygen, oxidization of 2,2â??-azinobis-(3-ethylbenzothiazoline-6-sulfonate) (ABTS) was performed at pH 5.5 and 25°C under anaerobic condition. While laccase catalysed oxidization of ABTS scarcely proceeded (<0.2% within 1800 s ) in the absence of electric field, the application of electric field enabled a continuous oxidation at a conversion rate of 32 μmol/min. Reproducible ABTS oxidation yield as well as cyclic voltammetry were obtained in 5 cycles. The continuous oxidation by laccase in the absence of oxygen, we believe, is attributed to the timely electron transfer by electricity to the active site of laccase through the nanowires inside the CN matrix and holds great promise for unprecedented applications.