Upgrading Kolbe electrolysis. Highly efficient production of green fuels and solvents by coupling biosynthesis and electrosynthesis

The chemical industry is transitioning to more sustainable and biobased processes. One key element of this transition is coupling energy fluxes and feedstock utilization for optimizing processes, routes and efficiencies. Here, we show for the first time the coupling of the Kolbe electrolysis at the anode with a subsequent microbial conversion of the cathodically produced co-product hydrogen. Kolbe electrolysis of valeric acid yields the liquid drop-in fuel additive n-octane. Subsequently, the solvent isopropanol is produced by resting Cupriavidus necator cells using gaseous electrolysis products (esp. CO${}_2$ and H${}_2$). The resting microbial cells show carbon efficiencies of up to 41 % and Coulombic/Faradaic efficiencies of 60 % and 80 % for anodic and cathodic reactions, respectively. The implementation of a paired electrolyser resulted in superior process performances with overall efficiencies of up to 64.4 %. (© 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH)