Microbial electrosynthesis offers a promising route for converting CO₂ into biodegradable polymers; however, its practical application is often limited by inefficient gas–liquid mass transfer, high energy input, and stringent nutrient control. In this study, an in situ electrolysis-driven gas-lift bioreactor was developed to enhance polyhydroxybutyrate (PHB) production from CO₂ using a hydrogen-oxidizing mixed microbial consortium. In situ electrochemical generation of H₂ and O₂ significantly improved gas–liquid mass transfer, enabling stable autotrophic growth and efficient carbon fixation. The effects of ammonium nitrogen (NH₄⁺–N) concentration on biomass growth, PHB accumulation, gas consumption, energy demand, and acid supplementation were systematically investigated. Increasing NH₄⁺–N promoted biomass growth, whereas synchronized limitation of ammonium and oxygen triggered rapid intracellular PHB accumulation. An intermediate NH₄⁺–N concentration of 250 mg L⁻¹ provided the optimal balance between growth and storage metabolism, yielding a PHB content of 59.1% and a PHB concentration of 1.65 g L⁻¹. Microbial community analysis revealed an Ancylobacter -dominated consortium that ensured metabolic robustness across varying nitrogen regimes. This work demonstrates an energy-efficient and scalable electrobiological platform for sustainable PHB production from CO₂. • Electrolysis-driven gas-lift reactor enables efficient CO₂-to-PHB microbial electrosynthesis； • In situ H₂ generation enhances gas–liquid mass transfer； • Coupled ammonium and oxygen limitation maximizes PHB content and accumulation rate； • Mixed hydrogen-oxidizing consortium ensures robust and scalable PHB production
Zhao et al. (Fri,) studied this question.