Production of Lactic Acid Directly from CO₂ by a Bioelectro-Hybrid System

Electrochemical CO2 reduction (ECO2R) is a pivotal strategy for addressing global carbon emissions while producing valuable chemicals. Despite their promise, conventional ECO2R processes are limited to simple C1 and C2 compounds. In this study, we present a bioelectro-hybrid system for the direct conversion of gaseous CO2 into l-lactic acid (l-LA), a versatile precursor for biodegradable polylactic acid. This system integrates a CO2 electrolyzer with metabolically engineered Escherichia coli, enabling the efficient bioconversion of formic acid (FA), derived from CO2, into l-LA under ambient conditions. A physiologically compatible catholyte was employed to facilitate continuous FA production while also serving as a medium for the engineered microbes' viability. By optimizing the catholyte composition, pH, nitrogen sources, and current density of the electrolyzer, l-LA was produced efficiently. Operating at optimal current density ensured a stable FA supply and maximized microbial conversion efficiency. This work presents the potential of a scalable platform for sustainable CO2 utilization into high-value chemicals, advancing bioelectro-hybrid technologies for biorefinery applications.