Chemoorganotrophic electrofermentation by Cupriavidus necator using redox mediators

Area of Science:

• Microbiology
• Bioelectrochemistry
• Biotechnology

Background:

• Cupriavidus necator is a versatile bacterium used in bioprocesses, typically using oxygen as a terminal electron acceptor.
• Aeration in microbial processes presents challenges like foam, cost, and safety concerns, particularly with hydrogen and oxygen.
• Bioelectrochemical systems offer an alternative by using electrodes as terminal electron acceptors, mitigating aeration issues.

Purpose of the Study:

• To establish mediated electron transfer (anodic respiration) from C. necator to an electrode.
• To identify effective redox mediators for anodic respiration using fructose as the electron and carbon source.
• To evaluate the functionality and inhibitory effects of various redox mediators in a C. necator bioelectrochemical system.

Main Methods:

• Cultivation of Cupriavidus necator in a bioelectrochemical system.
• Testing 11 common biological and non-biological redox mediators for electron transfer.
• Measurement of current density and coulombic efficiency to assess mediator performance.

Main Results:

• Mediated electron transfer was successfully established between C. necator and the anode.
• Ferricyanide at 15 mM yielded the highest current density (260.75 µAcm⁻²).
• A coulombic efficiency of 64.1% was achieved with ferricyanide.

Conclusions:

• Redox mediators are essential for enabling anodic respiration in C. necator.
• Ferricyanide is a highly effective mediator for anodic electron transfer in this system.
• This study provides a foundation for optimizing bioelectrochemical processes with C. necator.