Efficiency Estimates for Electromicrobial Production of Branched-chain Hydrocarbons

Abstract

Electromicrobial production is a process where microorganisms use electricity as a charge and energy source for the production of complex molecules, often from starting compounds as simple as CO2. The aviation industry is in need for sustainable fuel alternatives that can meet their requirements of high-altitude performance while also meeting 21stcentury carbon emissions standards. The electromicrobial production of jet fuel components with CO2-derived carbon provides a unique opportunity to generate jet fuel blends that are compatible with modern engines with net-neutral carbon emissions. In this study, we analyze the pathways necessary to generate single- and multi-branched-chain hydrocarbonsin vivoutilizing both extracellular electron uptake (EEU) and H2-oxidation as methods for electron delivery, the Calvin cycle for CO2-fixation and the ADO decarboxylation pathway. We find the maximum electrical-to-fuel energy conversion efficiencies for single- and multi-branched chain hydrocarbons areand. Utilizing this information, as well as previously collected predictions on straight-chain alkane and terpenoid biosynthesis, we calculate the efficiency of electromicrobial production of jet fuel blends containing straight-chain, branched-chain, and terpenoid components. Increasing the fraction of branched-chain alkanes in the blend from zero to 47% only lowers the electrical energy conversion efficiency fromto.