Systems-informed genome mining for electroautotrophic microbial production
Microbial electrosynthesis (MES) systems can store renewable energy and CO2 in many-carbon molecules inaccessible to abiotic electrochemistry. Here, we develop a multiphysics model to investigate the fundamental and practical limits of MES enabled by direct electron uptake and we identify organisms in which this biotechnological CO2-fixation strategy can be realized. Systematic model comparisons of microbial respiration and carbon fixation strategies revealed that, under aerobic conditions, the CO2 fixation rate is limited to <6 mol/cm2/hr by O2 mass transport despite efficient electron utilization. In contrast, anaerobic nitrate respiration enables CO2 fixation rates >50 mol/cm2/hr for microbes using the reductive tricarboxylic acid cycle. Phylogenetic analysis, validated by recapitulating experimental demonstrations of electroautotrophy, uncovered multiple probable electroautotrophic organisms and a significant number of genetically tractable strains that require heterologous expression of <5 proteins to gain electroautotrophic function. The model and analysis presented here will guide microbial engineering and reactor design for practical MES systems.