Direct CO<sub>2</sub> Transformation to Malate via Bioelectrosynthesis upon Engineered <i>Shewanella oneidensis</i>
Yixin Li, Dong Xia, Yinuo Xie, Rong Dong, Mingfeng Cao, Qingbiao Li, Yuanpeng Wang
Abstract
Microbial electrosynthesis (MES) offers a sustainable and low-carbon approach for CO 2 valorization, with Shewanella oneidensis ( S. oneidensis ) MR-1 identified as an ideal microbe for MES. However, no prior research has demonstrated that S. oneidensis MR-1 can directly metabolize CO 2 into multicarbon (C 2+ ) products due to its inability to perform the intracellular formate assimilation pathway. Here, we provide initial proof-of-concept evidence of direct bioelectrochemical CO 2 reduction to the C 4 product of malate. Specifically, the transformation of CO 2 to malate attains a notable production concentration of 1.18 mmol·L –1, marking the first instance of direct C 4 compound bioelectrosynthesis. Such remarkable CO 2 -to-C 4 conversion performances are attributed to the successful implementation of dual-plasmid systems in S. oneidensis MR-1, which facilitate the overexpression of the reductive glycine pathway (Plasmid I) for assimilating CO 2 -derived formate and the alternative malate biosynthetic pathway (Plasmid II) to channel metabolic intermediates toward the biosynthesis of malate. Advancing CO 2 valorization toward carbon-negative C 2+ bioproducts, our sophisticated dual-plasmid systems engineered in microbes can be further refined for scalable CO 2 bioelectrolysis with the objective of facilitating industrial applications.