Two-stage bioconversion of carbon monoxide to biopolymers via formate as an intermediate

Numerous industries discharge substantial amounts of carbon monoxide (CO) into the atmosphere as waste; utilizing CO-containing industrial waste gases to produce useful organic chemicals has recently attracted attention. Here, we constructed a two-stage biocatalytic CO-conversion system for producing poly-3-hydroxybutyrate (PHB), a promising degradable biopolymer. In the first stage, Acetobacterium woodii, an acetogenic bacterial strain containing CO dehydrogenase (CODH) and formate dehydrogenase (FDH), was used as a whole-cell biocatalyst to transform CO into formate independent of an external reducing agent, such as H₂. The conversion yield and specificity were close to 100% when the strain's energy metabolism was blocked to suppress acetate production. The resulting formate was fed to a second bioreactor, where it was converted to PHB by engineered Methylbacterium extorquens AM1. The two-stage bioconversion of CO to a valuable product via formate as an intermediate offers a novel and promising strategy for CO utilization.