Bioelectrochemical Study of Thermostable Pycnoporus sanguineus CS43 Laccase Bioelectrodes Based on Pyrolytic Carbon Nanofibers for Bioelectrocatalytic O-2 Reduction

摘要

In this study, the bioelectrocatalytic reduction of molecular oxygen by two highly thermostable laccase isoforms from a native strain of Pycnoporus sanguineus CS43 were evaluated and compared to commercially available laccase from Trametes versicolor (TvL). The laccase isoforms (LAC1 and LAC2) and TvL laccase were immobilized by orientation onto anthracene-modified multiwalled carbon nanotubes (AC-MWCNT), which were subsequently immobilized onto carbon nanofiber mat electrodes fabricated using a carbon MEMS (C-MEMS) process. The performances of the isoforms were evaluated at differing pHs, temperatures, and with various inhibitors under hydrodynamic and hydrostatic conditions. Both LAC1 and LAC2 had onset potentials of over +650 mV vs Ag/AgCl at pH 4.0, which are among the highest reported to date for any laccase bioelectrode. High current densities were also obtained, producing 825 +/- 88 mu A/cm(2) and 1220 +/- 106 mu A/cm(2) with LAC1 and LAC2, respectively. The bioelectrodes also demonstrated remarkable operational ranges in pH and temperature as well as increased resistance to common laccase inhibitors. In both cases, they maintained over 70% of their maximum current densities after 12 h of continuous operation at 20 degrees C and over 20% of their maximum current densities after 6 h of continuous operation at 45 degrees C. In comparison, the TvL cathodes maintained 50% of their maximum current densities after 12 h at 20 degrees C and lost all catalytic activity after 2 h at 45 degrees C. The high stability, onset potential, current densities, and increased inhibitor resilience demonstrated by the results of this study make these isoforms very attractive for applications such as biofuel cell cathodes.