Electro-Stimulated Dual-Species Catalysis Enables CO₂ Fixation Toward Selective 1,4-Butanedioic Acid Biosynthesis

Area of Science:

• Biotechnology and Bioengineering
• Synthetic Biology
• Sustainable Chemistry

Background:

• Succinic acid (SA) is a vital platform chemical, but its biocatalytic production faces challenges including redox imbalance, byproduct formation, and inefficient CO2 utilization.
• Existing methods for SA production are often limited by these constraints, hindering industrial scalability and sustainability.

Purpose of the Study:

• To overcome the limitations in SA biocatalytic production by developing an enhanced dual-species bioelectrocatalytic system.
• To improve SA yield, selectivity, and CO2 sequestration efficiency through synergistic microbial interactions and electro-fermentation.

Main Methods:

• Employed a dual-species co-culture system with Citrobacter amalonaticus (CA) and Bacillus subtilis (BS) in a bioelectrocatalytic setup.
• Utilized comprehensive gene-expression profiling to analyze metabolic pathway upregulation (PPC in CA, PYC in BS).
• Performed protein/structural modeling and docking to understand enzyme behavior under co-culture conditions. Assessed biogas composition and thermodynamic/electrochemical parameters.

Main Results:

• Achieved significantly enhanced SA production (0.6 g/g; 6 g/L) compared to monoculture systems.
• Demonstrated intensified carboxylation activity via the reductive tricarboxylic acid pathway, supported by upregulated PPC and PYC.
• Observed both extracellular and intracellular CO2 sequestration, evidenced by increased H2 in biogas and improved reactor stability/electron flow.

Conclusions:

• The developed hybrid bioelectrochemical strategy effectively leverages species-specific metabolic roles and electron-steering for high-yield, selective SA production.
• This approach offers a scalable and sustainable blueprint for carbon-based biomanufacturing, addressing key limitations of traditional biocatalysis.