Again (also SecondCircle Bio), a biotech company founded in Denmark in 2020, develops a gas fermentation technology that uses thermophilic bacteria in a bioreactor to transform carbon dioxide (COâ‚‚) from flue gasses into biofuels like acetate, acetone, and ethanol. This process not only cuts down on COâ‚‚ emissions, but it also makes green, sustainable fuels that can replace chemicals made from traditional fossil fuels.
Challenges
Carbon emissions and COâ‚‚ capture
Industrial carbon emissions contribute significantly to climate change. Apart from the traditional approach of carbon capture and storage from industrial flue gas, emerging technologies, such as Direct Air Capture (DAC), enhanced weathering, and Direct Ocean Capture, can remove excessive atmospheric CO₂. However, storing captured CO₂ underground has long-term ecological risks and a lack of economic viability, thus being increasingly viewed as an unsustainable way. However, converting captured CO₂ to value-added chemicals or sustainable fuels, instead of geological storage, is attracting more attention. Among technologies of carbon neutral fuels, microbial fermentation offers a circular solution.
Moorella thermoacetica for COâ‚‚ fixation
Acetogenic bacteria grow by consuming gaseous CO₂ (or CO). The process fixes CO₂. Thermophilic bacteria for CO₂ fixation at typical temperatures between 45 ºC and 80 ºC are of particular interest because they reduce risk of contamination with unwanted microorganisms, use less energy for cooling the fermentation system, have a faster production rate due to the advantageous thermodynamics, and lower capital and operational expenditures.
Moorella thermoacetica is a type of thermophilic bacteria that can turn COâ‚‚ gas into acetone and other useful chemicals. So, they have attracted significant interest in the applications in clean technology, renewable energy, and the production of fuels and other valuable chemicals.
Moorella thermoacetica is very good at fixing CO₂, but its growth rate is slow, which makes it less effective at fixing CO₂. Moorella thermoacetica is also sensitive to fluctuations in the gas supply and gradients in the industrial production bioreactor. If there aren’t enough nutrients or CO₂ gas in the bioreactor, Moorella thermoacetica can die or sporulate. This makes subcultures inactive and decreases the overall efficiency significantly.
Again Technology
Again has developed a biotechnology to increase the growth of a Moorella thermoacetica by deleting SpoOA gene and/or introducing genes to express a variant of SinR in the bacterium. This gene modification has increased the growth rates and decreased the lag phase duration of the Moorella thermoacetica, increasing their COâ‚‚ fixation and biochemical production efficiency. Through the optimization of trace elements in the fermentation medium and operational steps, Again uses Moorella thermoacetica for anaerobic microbial fermentation to efficiently convert COâ‚‚ into organic chemicals, transforming emissions into marketable products like biofuels or bioplastics.
