Beyond the farm: Making edible protein from CO₂ via hybrid bioinorganic electrosynthesis

Climate change and food shortage are two of the defining challenges in the coming decades. Considering that conventional approaches for protein production may associate with negative environmental impacts and greenhouse gas emissions, alternative protein sources that rely on inexhaustible substrates/energy should be pursued. In this proof-of-concept study, we propose a two-stage bioinorganic electrosynthesis process that can first convert CO₂ and excessive electricity into methane and then synthesize single-cell protein. 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. This process using renewable feedstocks was proved independent of conventional agriculture for protein production.