Bioelectrochemistry

Electron transfer as opposed to hydrogen transfer was demonstrated to be involved in the oxidation-reduction of the flavoprotein enzyme system. A bioelectrochemical investigation of glucose oxidase (EC 1.1.3.4), d-amino acid oxidase (EC 1.4.3.3), and yeast alcohol dehydrogenase (EC 1.1.1.1) systems was conducted in an attempt to utilize the electron-transferring process as a potential anodic reaction in a biochemical fuel cell. Utilizing a bio-fuel cell constructed of plexiglass, platinum-foil electrodes, and an ion-exchange membrane for conduction between the anolyte and catholyte, the flavoprotein enzymes, both glucose oxidase and d-amino acid oxidase systems in conjunction with an O₂ cathode, generated 175–350 mV. In contrast, alcohol dehydrogenase (yeast), a pyridinoprotein enzyme which requires coenzyme I (NAD+), did not produce any electrical voltage. Elemental iron was found to potentiate the flavoprotein enzyme reaction yielding voltages ranging from 625 to 750 mV. The potentiating effect was probably due to a faster turnover rate of FADH to FAD+ coupled with the additional net oxidation potential of iron.