Sustainable Oxygen Reduction Catalyzed by Whole-Cell Electro-Mutualism

Area of Science:

• Microbiology
• Bioelectrochemistry
• Sustainable Energy

Background:

• Oxygen reduction reaction (ORR) is vital for cellular energy but limited for sustainable applications due to inefficient electron transfer.
• Current methods for ORR often rely on precious metal catalysts, posing sustainability challenges.

Purpose of the Study:

• To explore an interspecies cooperative mechanism for efficient extracellular ORR.
• To investigate the potential of using genetically unmodified bacteria for metal-free ORR catalysis.

Main Methods:

• Utilized electrotrophic bacteria *Acinetobacter venetianus* RAG-1 and *Shewanella oneidensis* MR-1 under cathodic polarization.
• Investigated inorganic carbon assimilation and metabolite exchange between species.
• Analyzed flavin-mediated electron transfer enhancement via the RnfB complex.

Main Results:

• Achieved the highest reported whole-cell ORR current density (20.9 A/m²) under aerobic, neutral-pH conditions.
• Demonstrated a synergistic effect where RAG-1 provides fuel and MR-1 enhances electron transfer.
• Showcased the universality of electro-mutualism by substituting MR-1 with *Bacillus subtilis*.

Conclusions:

• Electro-mutualism offers a novel, metal-free catalytic strategy for green energy conversion.
• This microbial cooperation significantly enhances transmembrane electron transfer for efficient ORR.
• The findings pave the way for sustainable bioelectrochemical systems using unmodified microorganisms.