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Electro-biocatalytic conversion of carbon dioxide to alcohols using gas diffusion electrode

Srikanth, Sandipam, Singh, Dheer, Vanbroekhoven, K., Pant, Deepak, Kumar, Manoj, Puri, S.K., Ramakumar, S.S.V.
Bioresource technology 2018 v.265 pp. 45-51
acetic acids, biochemical pathways, butanol, butyric acid, carbon, carbon dioxide, electrodes, ethanol, mixed culture, pH, solubility, volatile fatty acids
Impact of gas diffusion electrodes (GDEs) was evaluated in enhancing the CO2 bio-availability for its transformation to C4-organics, especially to alcohols using selective mixed culture. Observed current density was more stable (9–11 A/m2) than submerged experiments reported and significantly varied with pH and respective CO2 solubility. Uncontrolled operating pH (starting with 8.0) showed its impact on shifting/triggering alternate metabolic pathways to increase the carbon length (butyric acid) as well as producing more reduced end products, i.e. alcohols. During the experiments, CO2 was transformed initially to a mixture of volatile fatty acids dominated with formic and acetic acids, and upon their accumulation, ethanol and butanol production was triggered. Overall, 21 g/l of alcohols and 13 g/l of organic acids were accumulated in 90 days with a coulombic efficiency (CE) of 49%. Ethanol and butanol occupied respectively about 45% and 16% of total products, indicating larger potential of this technology.