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

This study discusses the construction and operation of a membrane-less bioelectrochemical reactor that employs rotating working electrodes with a surface area of up to 1 m 2 . As a proof-of-principle for an aerobic microbial electrosynthesis process, Kyrpidia spormannii was cultivated in the reactor. Optical coherence tomography was used to examine the spatial distribution of the cathodic biofilm. After 24 days 87% of the cathode surface was covered with biofilm that was characterized by a radial increase in its biovolume towards the circumcenter of the electrodes reaching up to 92.13 μm 3 μm -2 . To demonstrate the versatility of the system, we further operated the reactor as a microbial electrolysis cell employing a co-culture of Shewanella oneidensis and Geobacter sulfurreducens . Anodic current densities of up to 130 μA cm -2 were measured during these batch experiments. This resulted in a maximum production rate of 0.43 liters of pure hydrogen per liter reactor volume and day. Graphical Abstract Highlights Construction of a 10 L membrane-less, pressurizable bioelectrochemical reactor Rotating working electrodes with up to 1 m 2 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