Herzog, JanJanHerzogMook, AlexanderAlexanderMookGuhl, LottaLottaGuhlBäumler, MiriamMiriamBäumlerBeck, Matthias H.Matthias H.BeckWeuster-Botz, DirkDirkWeuster-BotzBengelsdorf, Frank R.Frank R.BengelsdorfZeng, An-PingAn-PingZeng2022-10-102022-10-102023-01Engineering in Life Sciences 23 (1): e2100169 (2023-01)http://hdl.handle.net/11420/13728Acetobacterium woodii is known to produce mainly acetate from CO₂ and H₂, but the production of higher value chemicals is desired for the bioeconomy. Using chain-elongating bacteria, synthetic co-cultures have the potential to produce longer-chained products such as caproic acid. In this study, we present first results for a successful autotrophic co-cultivation of A. woodii mutants and a Clostridium drakei wild-type strain in a stirred-tank bioreactor for the production of caproic acid from CO₂ and H₂ via the intermediate lactic acid. For autotrophic lactate production, a recombinant A. woodii strain with a deleted Lct-dehydrogenase complex, which is encoded by the lctBCD genes, and an inserted D-lactate dehydrogenase (LdhD) originating from Leuconostoc mesenteroides, was used. Hydrogen for the process was supplied using an All-in-One electrode for in situ water electrolysis. Lactate concentrations as high as 0.5 g L–1 were achieved with the AiO-electrode, whereas 8.1 g L–1 lactate were produced with direct H₂ sparging in a stirred-tank bioreactor. Hydrogen limitation was identified in the AiO process. However, with cathode surface area enlargement or numbering-up of the electrode and on-demand hydrogen generation, this process has great potential for a true carbon-negative production of value chemicals from CO₂.en1618-286320231Wiley-VCHhttps://creativecommons.org/licenses/by/4.0/bioelectrochemical systemcarbon fixationcell–cell interactionconstraint-based modelingin situ electrolysisTechnikJournal Article10.15480/882.503010.1002/elsc.20210016910.15480/882.5030Journal Article