A scalable, Rotating Disc Bioelectrochemical Reactor (RDBER) suitable for the cultivation of both cathodic and anodic biofilms

This study presents the construction and operation of a membrane-less reactor suitable for different bioelectrochemical applications. The system employs rotating graphite disks as working electrodes with a total surface area of 1 m2. Given the reactor volume of 10 L, this results in a surface-to-volume ratio of 100:1 m2 m-3. Moreover, this rotating disk bioelectrochemical reactor (RDBER) is fully autoclavable, pressurizable to at least 0.5 bars and an optical window allows for in vivo monitoring of biofilm development on the electrodes by means of optical coherence tomography (OCT). As a proof-of-principle for an aerobic microbial electrosynthesis process, we cultivated the thermoacidophilic, electroautotrophic bacterium Kyrpidia spormannii in the RDBER and investigated the spatial distribution of the cathodic biofilm on the rotating working electrode by OCT. Thereby, biofilm heights of more than 75 μm were achieved. To demonstrate the versatility of the system, we further operated the reactor anodically as a microbial electrolysis cell employing a co-culture of Shewanella oneidensis and Geobacter sulfurreducens. Finally, the cultivation experiments with different electroactive microorganisms not only prove the basic functionality of the RDBER, but also illustrate that the RDBER can satisfy a wide range of biotechnological requirements for pure culture applications. Graphical Abstract Highlights Construction of a 10 L membrane-less, pressurizable bioelectrochemical reactor Rotating working electrodes with up to 1 m2 electrode surface Electroautotrophic cultivation and quantification of K. spormannii biofilms Initial cell density crucial for successful K. spormannii biofilm formation Anodic operation as MEC with Shewanella / Geobacter coculture