Electricity-driven CO₂-to-PHB conversion via enriched hydrogen-oxidizing bacterial consortia in a gas-lift bioreactor

Coupling water electrolysis with hydrogen-oxidizing bacteria (HOB) fermentation represents a promising strategy for sustainable polyhydroxybutyrate (PHB) production and CO₂ mitigation. In this study, a novel PHB-producing HOB consortium dominated by Acinetobacter was selectively enriched in a custom-designed gas-lift bioreactor supplied with electrolytic H₂ and O₂. The effects of nitrogen limitation, oxygen limitation, and combined nitrogen–oxygen dual limitation on PHB accumulation were systematically investigated. Results demonstrated that oxygen limitation more effectively promoted PHB accumulation compared to nitrogen limitation, while dual limitation yielded the highest PHB content (55.65% of CDW), comparable to pure cultures. Structural and compositional analyses verified successful PHB biosynthesis. Compared with reported pure and engineered strains, the enriched PHB-HOB community exhibited enhanced adaptability, lower cultivation costs, and promising scalability. These findings highlight the potential of mixed HOB consortia as an efficient and sustainable platform for PHB production from CO₂, offering valuable insights into electricity-driven carbon capture and biopolymer synthesis.