Direct CO₂ Transformation to Malate via Bioelectrosynthesis upon Engineered Shewanella oneidensis

Area of Science:

• Synthetic Biology
• Electromicrobiology
• Biotechnology

Background:

• Microbial electrosynthesis (MES) utilizes microbes for sustainable CO2 valorization.
• Shewanella oneidensis MR-1 is a model organism for MES but cannot naturally metabolize CO2 into multicarbon products.
• Existing methods lack direct CO2 conversion to C2+ products.

Purpose of the Study:

• To demonstrate direct bioelectrochemical CO2 reduction to C4 products using engineered S. oneidensis MR-1.
• To overcome the natural metabolic limitations of S. oneidensis MR-1 for CO2 assimilation.
• To establish a proof-of-concept for producing malate from CO2 via MES.

Main Methods:

• Engineered S. oneidensis MR-1 with dual-plasmid systems.
• Plasmid I: Overexpression of the reductive glycine pathway for CO2-derived formate assimilation.
• Plasmid II: Overexpression of an alternative malate biosynthetic pathway for channeling intermediates.
• Bioelectrochemical reduction of CO2 to malate.

Main Results:

• Achieved direct bioelectrochemical CO2 reduction to the C4 product, malate.
• Attained a notable malate production concentration of 1.18 mmol·L-1.
• First instance of direct C4 compound bioelectrosynthesis reported.

Conclusions:

• Successfully engineered S. oneidensis MR-1 to directly convert CO2 to malate using dual-plasmid systems.
• Demonstrated the potential for advanced CO2 valorization toward carbon-negative C2+ bioproducts.
• Engineered microbial systems show promise for scalable CO2 bioelectrolysis and industrial applications.