Fig. 6

Overview of the implemented modification in the metabolism of E. coli. a The knock-out of the genes frdA-D, adhE, ldh, pta, and ack inhibits the regeneration of NAD⁺. Furthermore, the anaerobic catabolism is forced to stop at the stage of pyruvate. b Accumulated pyruvate is converted to acetoin by the acetolactate synthase (AlsS) and the acetolactate decarboxylase (AlsD), expressed from a pMAL vector. c The surplus of respiratory electrons in the form of NADH is transferred to a carbon electrode. The C-type cytochromes CymA, Stc, and MtrA from Shewanella oneidensis enable the export of electrons into the periplasm. The electrons, transported into the periplasm, are transferred onto methylene blue (MB), a membrane-diffusible redox shuttle. Reduced methylene blue is reoxidized at the carbon electrode, which serves as a non-depletable terminal electron acceptor