Electrosynthesis of Organic Compounds from Carbon Dioxide Is Catalyzed by a Diversity of Acetogenic Microorganisms

Abstract

ABSTRACTMicrobial electrosynthesis, a process in which microorganisms use electrons derived from electrodes to reduce carbon dioxide to multicarbon, extracellular organic compounds, is a potential strategy for capturing electrical energy in carbon-carbon bonds of readily stored and easily distributed products, such as transportation fuels. To date, only one organism, the acetogenSporomusa ovata, has been shown to be capable of electrosynthesis. The purpose of this study was to determine if a wider range of microorganisms is capable of this process. Several other acetogenic bacteria, including two otherSporomusaspecies,Clostridium ljungdahlii,Clostridium aceticum, andMoorella thermoacetica, consumed current with the production of organic acids. In general acetate was the primary product, but 2-oxobutyrate and formate also were formed, with 2-oxobutyrate being the predominant identified product of electrosynthesis byC. aceticum. S. sphaeroides,C. ljungdahlii, andM. thermoaceticahad high (>80%) efficiencies of electrons consumed and recovered in identified products. The acetogenAcetobacterium woodiiwas unable to consume current. These results expand the known range of microorganisms capable of electrosynthesis, providing multiple options for the further optimization of this process.