Redox mediator interaction with Cupriavidus necator – spectroelectrochemical online analysis

Bioelectrochemical systems with Cupriavidus necator present a viable solution for harnessing H2/CO2 mixtures as substrates, employing mediated electron transfer to an infinite electron acceptor in the form of an anode instead of O2. Fourteen redox mediators were spectroelectrochemically characterized, and their efficiency was evaluated through screening with C. necator in common cuvettes with screen printed electrodes (e-Cuvettes). Key performance indicators, including total turnover number, reduction rate, and growth, were analyzed. Ferricyanide emerged as highly effective for anodic respiration, reaching a total turnover number of 8.38 over 120 h of cultivation. On the other hand, phenazine methosulfate exhibited the highest reduction rate at 2.49 mM h−1 with a total of 5.16 turnovers. Contrary, growth impairment is reported for menadione, possibly leading to deficient anodic electron transfer. The utilization of a broad spectrum of these shuttle molecules highlights the potential for optimizing bioelectrochemical applications involving C. necator.