Bioeletrodo Cooperativo para Bioprodução e Oxidação de Etanol

The development of electrochemical devices based on biomolecules arose due to the great interest in its potential application in many areas, such as amperometric biosensors, implantable biodevices for power generation or biofuel cells [1,2]. In this work, we report the development of an electrode composed of flexible carbon fibers array that have both alcohol dehydrogenase (ADH) and Saccharomyces cerevisiae yeast adsorbed on it to apply as cooperative biocatalysts for oxidation of ethanol. The advantage of using Saccharomyces cerevisiae as biocatalyst is its ability to operate under aerobic and anaerobic conditions, since it is a microorganism with well understood metabolism and optimal biological condition at room temperature. The bioelectrocatalytic performance was evaluated during 24 hours of fermentation by cyclic voltammetry (CV), and the ethanol produced during this fermentation was quantified by gas chromatography (GC). First, samples were collected containing glucose and yeast in suspension for 24 hours of fermentation, which then underwent to chromatographic analysis in order to quantify the ethanol produced. Electrochemical studies demonstrated that enzyme and yeast operate as a cooperative biocatalyst during the indirect oxidation of glucose, in which ethanol is produced through alcoholic fermentation by glycolysis route and then is oxidized by the ADH immobilized on the electrode surface. This bioelectrode is able to oxidize ethanol which results in the oxidation of nicotinamide adenine dinucleotide, NADH, to the oxidized form, NAD+. Comparing the ethanol concentration obtained from GC and the current density from CV during the experiment, it was possible to observe a similar response. Thus, to better evaluate this behavior, we fitted these values using an exponential function to relate and analyze the profile of both curves. The results demonstrated a linear correlation between the ethanol concentration and current generated. Therefore, the biosystem proposed here has introduced a concept that enzyme and microorganisms can work cooperatively to produce a new class of bioelectrodes for biofuel cell applications with improved power outputs.