Carbon-nanotube-caged microbial electrodes for bioelectrocatalysis.

Area of Science:

• Bioelectrochemistry
• Microbial fuel cells
• Nanomaterials in catalysis

Background:

• Developing stable and efficient microbial electrodes is crucial for bioelectrochemical systems.
• Immobilization techniques often face challenges with long-term stability and catalytic activity.
• Methylobacterium extorquens AM1 possesses formate dehydrogenase enzymes relevant for bioelectrocatalysis.

Purpose of the Study:

• To develop a method for stable microbial cell immobilization on electrode surfaces.
• To investigate the bioelectrocatalytic activity of immobilized Methylobacterium extorquens AM1.
• To assess the long-term stability of the developed microbial electrode.

Main Methods:

• Microbial cells (Methylobacterium extorquens AM1) were immobilized within multiwalled carbon nanotubes (MWNTs).
• The MeAM1-MWNTs mixture was dried onto electrode surfaces to form the microbial electrode.
• Bidirectional bioelectrocatalysis (formate oxidation and CO2 reduction) was measured using methyl viologen as a mediator.

Main Results:

• The MeAM1-MWNTs electrode exhibited stable and efficient bidirectional bioelectrocatalysis.
• Steady-state catalytic current densities of 0.6 ± 0.1 mA cm⁻² for formate oxidation and -0.8 ± 0.1 mA cm⁻² for CO2 reduction were achieved.
• The electrode maintained its catalytic signal stability for over one week of continuous operation under mild conditions (pH 7.0, 37°C).

Conclusions:

• Stable immobilization of microbial cells on electrodes is achievable using MWNTs as a caging material.
• The developed MeAM1-MWNTs electrode demonstrates significant potential for applications in bioelectrochemical systems.
• The method offers a robust platform for creating durable and active microbial electrodes for catalysis.