Bioinorganic electrosynthesis of single-cell protein from CO2 and green electricity

Climate change and food shortage due to the growing world population are two of the biggest challenges for the transition to a low-carbon economy in the coming decades. In this study, we propose a promising two-stage bioinorganic electrosynthesis process that can first convert CO2 and renewable electricity into methane and then synthesize single-cell protein, as an alternative solution to address these challenges. With an external voltage of 3.5 V and a CO2 inflow rate of 50 mL·d-1, it was possible to produce methanotrophic biomass of 118.7 ± 9.2 mg·L-1 with an amino acids mass-content of 54.6 ± 8.3%, resulting in nitrogen assimilation and CO2 conversion efficiency of 91.0 ± 1.3% and 71.0%. The applied voltages, CO2 inflow rates, and O2 supply were found to affect the process significantly. The outcomes will lead to sustainable protein production, CO2 mitigation, and valorization of renewable electricity, which are perfectly in line with the United Nations Sustainable Development Goals (2, 6, 7, 8, 9, 13, 14, 15).