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

Succinic acid (SA)/1,4‐Butanedioic acid is a key platform‐chemical with broad industrial relevance, yet its biocatalytic production is constrained by redox imbalance, by‐product accumulation, and limited CO 2 sequestration. This study overcomes the above limitations and enhanced the SA production (0.6 g g −1 ; 6 g L −1 ) by dual‐species catalysis using Citrobacter amalonaticus (NCIM 5782, CA) and Bacillus subtilis (BS, NCIM 5781), in a bioelectrocatalytic system. Comprehensive gene‐expression‐profiling revealed upregulation of phosphoenolpyruvate carboxylase ( ppc /PPC) in CA and pyruvate carboxylase ( pyc /PYC) in BS, reflecting intensified carboxylation activity via the reductive tricarboxylic acid pathway. Protein/structural modeling/docking of PPC and PYC demonstrated enhanced catalytic‐site exposure under electro‐fermentative co‐culture conditions, correlating with greater carboxylation efficacy. Notably, beyond extracellular‐CO 2 fixation, intracellular‐CO 2 sequestration is also evident, as indicated by a marked enrichment of H 2 in the biogas produced during dual‐species‐catalysis compared to monoculture systems. Thermodynamic and electrochemical evaluation indicated greater stability and electron flow in co‐culture reactors (R9:ΔG = −42.29 kJ) compared to monocultures. Collectively, this study presents a scalable hybrid bioelectrochemical strategy leveraging species‐specific metabolic roles and electron‐steering to facilitate high‐yield, selective SA production, offering a promising blueprint for sustainable carbon‐based biomanufacturing.