Mitochondrial origin of extracelullar transferred electrons in yeast-based biofuel cells

• Yeast biofuel cell current generation is suppressed by rotenone and antimycin A.
• A decrease of 39% in the electric charge is obtained in the presence of antimycin A.
• This reduction fits the aerobic respiration share in the overall yeast catabolism.
• The decreased COX and NADH dehydrogenase activities show mitochondrial dysfunction.
• Methylene blue partially neutralizes the inhibition effect of the rotenone.

The influence of mitochondrial electron transport chain inhibitors on the electricity outputs of Candida melibiosica yeast-based biofuel cell was investigated. The addition of 30 μM rotenone or antimycin A to the yeast suspension results in a decrease in the current generation, corresponding to 25.7 ± 1.3%, respectively 38.8 ± 1.9% reduction in the electric charge passed through the bioelectrochemical system. The latter percentage coincides with the share of aerobic respiration in the yeast catabolic processes, determined by the decrease of the ethanol production during cultivation in the presence of oxygen compared with that obtained under strict anaerobic conditions. It was established that the presence of both inhibitors leads to almost complete mitochondrial dysfunction, expressed by inactivation of cytochrome c oxidase and NADH:ubiquinone oxidoreductase as well as reduced electrochemical activity of isolated yeast mitochondria. It was also found that methylene blue partially neutralized the rotenone poisoning, probably serving as alternative intracellular electron shuttle for by-passing the complex I blockage. Based on the obtained results, we suppose that electrons generated through the aerobic respiration processes in the mitochondria participate in the extracellular electron transfer from the yeast cells to the biofuel cell anode, which contributes to higher current outputs at aerobic conditions.

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