Bio-Electrocatalytically Regulated Selective Succinic Acid Production by Suppressing Pyruvate Channel Using Glycerol and CO2

Abstract

Succinic acid (SA), an important industrial chemical, is traditionally produced via petrochemicals, generating significant greenhouse gases. Thus, the transition to sustainable biomanufacturing is critical for reducing emissions. However, a major challenge in bio-based SA production at an industrial scale is the generation of acetic acid (AA) as a byproduct, which reduces the SA yield and process efficiency. In this study, we demonstrated the potential of electro-fermentation (EF) as an innovative method for selective SA from Citrobacter amalonaticus (IICTSVMSA1) in a nongenetic approach with glycerol (30 g/L), MgCO₃ (10 g/L) and CO₂ (0.093 L/100 mL) as feedstocks. By downregulating the pyruvate dehydrogenase (ace) gene (regulating the pyruvate channel) with an electrode assembly and poised potential (−0.6 V), the production of AA was reduced by 30%. This resulted in a higher SA titer (17.4 g/L; 0.58 g/g) compared to our control condition (7.4 g/L; 0.25 g/g). We further performed sustainability analysis and planetary boundaries assessment, which revealed that the petrochemical process for SA production emits 3 times more CO₂ (6.9 kg/eq) and has a more environmental impact compared to the biological route (glucose─2.9 kg/eq; glycerol─2.4 kg/eq). Our findings can underscore the potential of EF toward selective SA production, which can be used in the bio-based SA-producing industries where product selectivity and down-streaming are crucial challenges.