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.