Improving the Direct Electron Transfer Efficiency in Laccase Electrodes for Biofuel Cell Cathodic Reactions

ITQB Seminar

Title: Improving the Direct Electron Transfer Efficiency in Laccase Electrodes for Biofuel Cell Cathodic Reactions

Speaker: Marcos Pita

Affiliation: Instituto de Catalisis y Petroleoquimica, CSIC, Madrid

Host: Inês Cardoso Pereira - Bacterial Energy Metabolism Lab

Abstract:

Fungal laccases are one of the best candidates for enzymatic biofuel cell cathodes due to its ability to reduce O2 directly to H2O at high potentials; laccases are also suitable for direct electron transfer when appropriately wired toward different electroactive surfaces such as gold or graphite.

However, laccase faces several hindering conditions when taking to many in  vivo-like environments, being the most relevant chloride inhibition and the functional pH. Chloride anions are a reversible inhibitor of laccase and are present in most biological fluids. Additionally, the typically acidic pH-optima for laccase performance take any laccase-modified electrode out of range for many natural fluids.

This presentation will show strategies to improve laccase performance under these nonfavoured environments. It has been shown that specific orientation of laccase for DET can reduce this inhibition source when immobilized on a low-density graphite (LDG) electrode1 and how to extend this immobilization method to gold planar electrodes2. We will show the improvement brought to current density and chloride resistance by combining a LDG electrode with gold nanoparticles. The limitations brought by the use of neutral pH can be addressed by generation of a local acidic pH environment. This has been achieved by inserting the laccase electrode in a  magnetic ring that allows the deposition of magnetic nanoparticles carrying another enzyme able to acidify the environment.3 For conceptual purposes we have used glucose oxidase (GOx) to produce a gluconic-acid environment, managing to lower pH 2 units while keeping the bulk pH neutral and therefore allowing laccase to work. Catalase was present for oxygen-regeneration purposes.

References:

1. Cristina Vaz-Dominguez, Susana Campuzano, Olaf Rüdiger, Marcos Pita, Marina Gorbacheva, Sergey Shleev, Victor M. Fernandez, Antonio L. De Lacey. Biosensors and Bioelectronics, 24, (2008), 531–537.
2. Marcos Pita, Cristina Gutierrez-Sanchez, David Olea, Marisela Velez, Cristina Garcia-Diego, Sergey Shleev, Victor M. Fernandez, Antonio L. De Lacey. Journal of Physical Chemistry C, 27, (2011), 13420- 13428.
3. Sylvain Clot, Cristina Gutierrez-Sanchez, Sergey Shleev, Antonio L. De Lacey, Marcos Pita. Electrochemistry Communications, 18, (2012), 37-40.