Novel electron transfer pathways in Ralstonia eutropha

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The well-characterized Gram-negative bacterium Ralstonia eutropha is capable in utilizing a wide array of heterotrophic carbon sources, but it is renowned for its ability to fix CO2 under chemolithoautotrophic conditions. Due to its flexible metabolism and the increasing availability of tools for its genetic engineering, it receives rapidly growing interest for biotechnological application. In fact, metabolically engineered R. eutropha strains have already been shown to produce various chemicals and biopolymers under autotrophic conditions. Nevertheless, upscaling of H2/O2-based autotrophic cultivation is risky due to potential formation of explosive gas mixtures (oxyhydrogen, “Knallgas”), which results in rigorous safety requirements. Furthermore, the CO2 fixation efficiency is lower in the presence of O2, due to an oxygenase side reaction of the CO2-fixing enzyme RuBisCO. These issues can be circumvented by the use of alternative electron acceptors substituting O2. In this proposal, a bioelectrochemical system (BES) will be investigated with regard to its use as an extracellular electron acceptor. Furthermore, reversibility of the novel electron transfer systems will be explored for their potential to be exploited in cathode-driven electrosynthesis approaches. In this the project, the expertise of the Lenz/Frielingsdorf group (microbiology, molecular biology and biochemistry of R. eutropha) and the Holtmann group (biochemical and electrochemical engineering, electrobiotechnological production processes with R. eutropha) will be combined to connect the cellular redox metabolism of R. eutropha with suitable electrodes to establish a novel, safe, versatile, and highly efficient production platform.