Bioanode with alcohol dehydrogenase undergoing a direct electron transfer on functionalized gold nanoparticles for an application in biofuel cells for glycerol conversion

In this paper we designed and investigated bioanode with alcohol dehydrogenase (ADH) catalysing oxidation of glycerol and glyceraldehyde. The most effective bioanode was fabricated when ADH was immobilized on gold nanoparticles (AuNPs) modified with 4-aminothiophenol. This electrode catalysed the oxidation of both glycerol and glyceraldehyde thus demonstrating a consecutive two-step process. The bioanode generated the current density of 510 mu A cm(-2) at pH 7.0 and 0 V vs. SCE. It was demonstrated that the electrode acted effectively due to the direct electron exchange between heme of ADH and modified AuNPs. The reversible oxidation and reduction of ADH heme proceeded at around -0.05 V vs. SCE. The turnover number of the immobilized enzyme was estimated to be 65 s(-1) which is the same as the catalytic number of the enzyme in solution. To the best of our knowledge those parameters are the highest currently reported for the alcohol dehydrogenase bioanodes operating utilizing a direct electron transfer. As a proof of biofuels cell conception, the bioanode was combined with AuNPs-lactase biocathode. The biofuel cell generated maximum power output of 130 mu W cm(-2) at 0.5 V and pH 7.0.