High acetate titer obtained from CO2 by thermophilic microbial electrosynthesis with Thermoanaerobacter kivui

Abstract

Novel renewable platforms for production of organic molecules need to be developed and deployed to achieve a circular carbon economy. Microbial electrosynthesis (MES) is a promising technology to produce acetate from CO2 and renewable electricity. However, productivity and product titer improvements are needed for electroacetogenesis to compete with other production methods. Here, we report the production of high concentrations of acetic acid by Thermoanaerobacter kivui in a continuous, H2-mediated, and thermophilic microbial electrosynthesis process. Acetate titers correlated inversely with the production rate: 490 mM (29.4 g L−1) acetate were produced at a production rate of 5.66 mM h−1 (0.34 g L−1 h−1) whereas 390 mM (23.4 g L−1) acetate were produced at a production rate of 12.75 mM h−1 (0.76 g L−1 h−1). This indicates that electrosynthesis rates are limited by product inhibition rather than electron donor supply at high acetate concentrations.