An electrified small-scale bioreactor for different cultivation modes and adaptive laboratory evolution of Cupriavidus necator

Electrobiotechnology is increasingly recognized as a key platform technology for sustainable production processes, as it allows direct coupling of renewable electricity with biocatalysis, driving selective chemical transformations. One remaining challenge is the development of suitable reactors fulfilling both electrochemical and biocatalysis requirements. Conventional setups, often used as proof-of-concept, often represent negative examples regarding scalability and industrial relevance. Scalable, electrified bioreactors are needed for screening purposes and for large-scale bioproduction. This study presents a small-scale, electrified bioreactor (V = 20 mL) that can facilitate a variety of electrochemical conditions and bioprocess modes. Two reactor configurations based on the commercial Pioreactor® were established: a two-electrode one-chamber system for electro-autotrophic growth via in situ hydrogen production, and a three-electrode two-chamber system for anodic respiration via mediated electron transfer. Additionally, it was used for electrochemical adaptive laboratory evolution (eALE). Under turbidostatic electro-autotrophic conditions with gradually increasing sodium sulphate concentrations, an osmo-tolerant strain was obtained within 10 d. The adapted variant exhibited improved growth at 300 mM sodium sulphate compared to the parental strain, including reduced lag-phase and a higher final optical density. Cupriavidus necator was used as a model organism. Overall, the results suggest that the system establishes a viable connection between microtiter plates and established liter-scale bioreactor operations.