The potential of CO2-based production cycles in biotechnology to fight the climate crisis

Abstract

Rising CO₂ emissions have pushed scientists to develop new technologies for a more sustainable bio-based economy. Microbial conversion of CO₂ and CO₂-derived carbon substrates into valuable compounds can contribute to carbon neutrality and sustainability. Here, we discuss the potential of C1 carbon sources as raw materials to produce energy, materials, and food and feed using microbial cell factories. We provide an overview of potential microbes, natural and synthetic C1 utilization pathways, and compare their metabolic driving forces. Finally, we sketch a future in which C1 substrates replace traditional feedstocks and we evaluate the costs associated with such an endeavor.

Fig. 1. Natural carbon fixation pathways.

XuMP Xylulose monophosphate, RuMP Ribulose monophosphate, G3P glyceraldehyde 3-phosphate, AcCoA acetyl CoA, PYR pyruvate, MeOH methanol, FA formate, FALD formaldehyde. Purple: methanol, formate, or formaldehyde fixing pathways, Blue: CO₂- fixing pathways, Yellow: linear pathways, Green: cyclic pathways. Note that the serine cycle and rGlycine pathway are mixed pathways that incorporate CO₂ in addition to methanol and formate.

Fig. 2. Potential and constraints for C1 feedstocks in the fuel, material, and food and feed sectors.

Each sector has a significant carbon fixing potential and is biotechnologically accessible. However, energy consumption and economic feasibility are viewed as hurdles for C1 feedstock implementation, as inexpensive resources have been utilized in all three sectors up to this point. Each sector’s carbon content is provided, indicating the possibility for carbon fixation. For that, the average carbon content was calculated of common fuels (methane, propane, butane, gasoline, diesel, kerosene, heavy fuel oil, ethanol and methanol) and of the six most common plastics (PET, HDPE, PVC, LDPE, PS, PP). In the case of food and feed, a default value for dry biomass was used. Using annual global production values for crude oil, plastics, food (at the consumers table, without any losses) and feed, an estimation of each carbon content is given for each sector in tons per year carbon (t/a C). Icons for illustrating each sector were provided by Freepik (Fuels), Smahicons (Materials) and FBJan (Food &Feed) at https://www.flaticon.com/.