Induced-fit binding of laccase to gold and carbon electrodes for the biological fuel cell applications

Analogues of laccase natural substrates (syringic, veratric, ferulic, vanillic, isovanillic, 3,5-dimethoxybenzoic aldehydes) were employed to bind and orient laccase molecules in a way which facilitates adsorption of the catalyst molecules and their electrical connection with the conductive support. Laccase was bound efficiently to these substrates both on gold and carbon electrodes forming, respectively, 2D and 3D films sensitive to oxygen. Gold electrodes were used for the surface plasmon resonance evaluation of the extent of laccase binding. Glassy carbon electrodes covered with single-wall carbon nanotubes (SWCNTs) covalently modified with laccase were shown to lead to higher catalytic reduction currents than the bare carbon nanotubes deposited in a similar film at the electrode. SWCNTs with ferulic group chosen for the practical application of the biocathode in the air-zinc biobattery allowed to improve its performance both in terms of power and stability in time. The open circuit potential of the cell was 1.71 ± 0.05 V and the maximum power density achieved was 5.1 mW/cm2 at 0.6 V.

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