A Comprehensive Modeling Analysis of Formate-Mediated Microbial Electrosynthesis*.

Mediated microbial electrosynthesis (MES) represents a promising strategy for the capture and conversion of CO into carbon-based products. We describe the development and application of a comprehensive multiphysics model to analyze a formate-mediated MES reactor. The model shows that this system can achieve a biomass productivity of ∼1.7 g L  h but is limited by a competitive trade-off between O gas/liquid mass transfer and CO transport to the cathode. Synthetic metabolic strategies are evaluated for formatotrophic growth, which can enable an energy efficiency of ∼21 %, a 30 % improvement over the Calvin cycle. However, carbon utilization efficiency is only ∼10 % in the best cases due to a futile CO cycle, so gas recycling will be necessary for greater efficiency. Finally, separating electrochemical and microbial processes into separate reactors enables a higher biomass productivity of ∼2.4 g L  h . The mediated MES model and analysis presented here can guide process design for conversion of CO into renewable chemical feedstocks.