Coupling of CO₂ Electrolysis with Parallel and Semi-Automated Biopolymer Synthesis - Ex-Cell and without Downstream...

Area of Science:

• Biotechnology
• Electrochemistry
• Chemical Engineering

Background:

• Developing sustainable methods for carbon dioxide (CO2) utilization is crucial for environmental remediation.
• Polyhydroxybutyrate (PHB) is a biodegradable polymer with diverse applications.
• Efficiently coupling CO2 reduction with microbial synthesis is a key challenge.

Purpose of the Study:

• To improve the integrated process of electrochemical CO2 reduction to formate and its microbial conversion to PHB.
• To optimize electrosynthesis parameters and microbial conversion for higher yields.
• To assess the scalability and potential for technical exploitation of the combined process.

Main Methods:

• Optimized Sn-based gas diffusion electrodes for CO2 electroreduction to formate.
• Developed a semi-automated system for formate feeding into bioreactors.
• Scaled up microbial conversion of formate to PHB by Cupriavidus necator from shake flasks to bioreactors.

Main Results:

• Achieved nearly 80% Faradaic efficiency for CO2 to formate conversion at 150 mA cm-2.
• Generated high-concentration formate feedstock (441±9 mmol L-1) without intermediate purification.
• Obtained a PHB to formate ratio of 16.5±4.0 mg g-1 and a PHB synthesis rate of 8.4±2.1 mg L-1 OD-1 h-1.
• Achieved an overall CO2 to PHB process yield of 22.3±5.5%, nearly doubling previous results.

Conclusions:

• The optimized integrated process significantly enhances CO2 to PHB conversion efficiency.
• The findings provide a robust basis for the technical application of CO2 valorization into bioplastics.
• This work demonstrates a promising pathway for sustainable biopolymer production from CO2.