The reactor systems used for microbial electrosynthesis, i.e. bioelectrochemical systems for achieving bioproduction so far reported in literature are relatively small in scale and highly diverse in their architecture and modes of operation. The often diverging requirements of the electrochemical and the biological processes and the interdisciplinarity of the field make the engineering of these systems a special challenge. This has led to multiple, differently optimized approaches of reactor vessels, designs and operating conditions making standardization and normalization or even a systematic engineering almost impossible. Overcoming this lack of standardization, scalability and knowledge‐driven engineering is the driving force for this work introducing an upgrade kit for bioreactors transforming these reversibly to bioelectroreactors. The prototypes of the bioreactor upgrade kit were integrated with commercial bioreactor (fermentor) systems and performances compared to a classic, small‐scale bioelectrochemical glass cell system. The use of the upgrade kit allowed interfacing with the existing infrastructure of the conventional bioreactors for growing electroactive microorganisms in pure culture conditions, with the added electrochemical control and further process monitoring. The results of growing Shewanella oneidensis MR‐1 clearly show that these systems can be used to control, monitor, and scale microbial bioelectrochemical processes, providing better resolution of the data for the tested experimental conditions.

The fluctuation and decentralization of renewable energy have triggered the search for respective energy storage and utilization. At the same time, a sustainable bioeconomy calls for the exploitation of CO as feedstock. Secondary microbial electrochemical technologies (METs) allow both challenges to be tackled because the electrochemical reduction of CO can be coupled with microbial synthesis. Because this combination creates special challenges, the electrochemical reduction of CO was investigated under conditions allowing microbial conversions, that is, for their future use in secondary METs. A reproducible electrodeposition procedure of In on a graphite backbone allowed a systematic study of formate production from CO with a high number of replicates. Coulomb efficiencies and formate production rates of up to 64.6±6.8 % and 0.013±0.002 mmol h cm , respectively, were achieved. Electrode redeposition, reusability, and long-term performance were investigated. Furthermore, the effect of components used in microbial media, that is, yeast extract, trace elements, and phosphate salts, on the electrode performance was addressed. The results demonstrate that the integration of electrochemical reduction of CO in secondary METs can become technologically relevant.

The growth of anodic electroactive microbial biofilms from waste water inocula in a fed-batch reactor is demonstrated using a three-electrode setup controlled by a potentiostat. Thereby the use of potentiostats allows an exact adjustment of the electrode potential and ensures reproducible microbial culturing conditions. During growth the current production is monitored using chronoamperometry (CA). Based on these data the maximum current density (j max ) and the coulombic efficiency (CE) are discussed as measures for characterization of the bioelectrocatalytic performance. Cyclic voltammetry (CV), a nondestructive, i.e. noninvasive, method, is used to study the extracellular electron transfer (EET) of electroactive bacteria. CV measurements are performed on anodic biofilm electrodes in the presence of the microbial substrate, i.e. turnover conditions, and in the absence of the substrate, i.e. nonturnover conditions, using different scan rates. Subsequently, data analysis is exemplified and fundamental thermodynamic parameters of the microbial EET are derived and explained: peak potential (E p ), peak current density (j p ), formal potential (E f ) and peak separation (ΔE p ). Additionally the limits of the method and the state-of the art data analysis are addressed. Thereby this video-article shall provide a guide for the basic experimental steps and the fundamental data analysis.

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Primary microbial electrochemical technologies are utilizing the interfacing of microbial redox reactions and electrodes. Based on its exploitation as recognition element for bioelectrochemical glucose sensors and inspired by its biotechnological potential Gluconobacter oxydans was studied on its suitability for microbial electrosynthesis. It is demonstrated that in bioelectroreactors the conversion of glucose by G. oxydans based on mediated extracellular electron transfer is not related to electric current flow. Oxidation current can only be recorded after preceding aeration phase, but the response does strongly depend on the microbial activity status, pO2 and gas supply as well as the pH regime. It is proven that the electric current is derived from the microbial cells, but the mechanism still needs to be elucidated. The suitability of G. oxydans for microbial electrosynthesis but also for bioelectrochemical sensors is critically assessed.

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