Challenges Facing Biofuel, SAF, & Syngas Fermentation

Methods like bioethanol fermentation, alcohol-to-jet (ATJ) and biomass-to-liquid (BtL) require the breaking down or gasification of biomass utilizing biological agents to generate compounds of industrial interest. Traditional fermentation methods often struggle with poor gas solubility, limiting microbial activity, and slowing biofuel and SAF production.

Resulting in:

• Low yields
• Low gas solubility
• Poor reproducibility
• High production costs
• Low volumetric productivity

• Renewable PtL Systems
• Biomass Gasification Plants
• Industrial Waste Gas Capture
• CO₂-based biomanufacturing
• Pilot testing for next-gen biofuel R&D.
• Syngas fermentation for bioethanol production.
• CO₂, H₂, or CO fermentation for sustainable aviation fuel.

Objective: A research group investigating gas fermentation optimization methods wanted to achieve high concentrations of isopropanol using a genetically modified Cupriavidus necator to ferment gaseous feedstocks CO₂ and H₂.

Requirements: Utilizing a bench scale, parallel bioreactor (100 – 400 ml), the research group required an automated, safe, and highly configurable system to grow an engineered autotrophic strain, with 4 independent gas feeds, providing the ability to generate a high gas-mass transfer to reach high cell and isopropanol titres (g L^-1) from CO₂. Ensuring safety levels between 2-6% O₂ for efficient metabolism and avoiding explosive conditions was crucial.

Solution: Gases are notoriously difficult to dissolve into liquid. However, pressurized reactors can improve their solubility, increasing feedstock availability. Additionally, hydrogen is highly explosive in the presence of oxygen, so strict control of these gases was fundamental to achieve isopropanol efficiently and safely. The BioXplorer 400P was equipped with three sets of gas feeds: Air, CO₂ and H₂. A fourth gas feed (N₂) was installed as safety system. Various probes and feeds were integrated to monitor and automatically deliver adjustments to the reactor, providing optimal growth and safety conditions for their continuous fermentation.

Results: Isopropanol was produced at comparable levels to traditional methods using a cheaper and more sustainable source CO₂ and H₂ instead of fructose, decreasing feedstock-derived costs by up to 60%.