Episode Summary

Supercritical carbon dioxide and bacteria that can grow in it make a great combination for biofuel production!

Microbe of the episode

Flexibacter aggregans

Jesse's takeaways

Biofuels are an important part of humanity's move away from non-renewable resources. They have a higher energy density than batteries are yet able to achieve, giving them significant advantages for transportation purposes in which tapping into an electric grid isn't possible. Depending on the biofuel, they also have the advantage of existing infrastructure: we don't need to build a whole new system of charging or refueling stations, but can use the systems already in place.

However, biofuels as a collection of technologies still need some refinements. Yields for the more potentially sustainable approaches are low, and the lower the concentration of a soluble fuel, the more difficult it is to separate it from the non-fuel components of a fermentation. Microbial products also face the risk of contamination of a fermentation by unwanted organisms that use up the substrate without producing desirable products.

In this study, supercritical carbon dioxide is considered as a fix for both of these problems. The gas is pressurized to a point at which it is indistinguishable from liquid. A strain of Bacillus megaterium is specially selected as capable of growing and fermenting in this environment, while contaminants are inhibited. The solvent potential of supercritical carbon dioxide also serves as a way to extract the biofuel product—in this case, isobutanol—from the aqueous part of the culture medium. While it needs some development, this approach yields promising results.

Journal Paper

Boock JT, Freedman AJE, Tompsett GA, Muse SK, Allen AJ, Jackson LA, Castro-Dominguez B, Timko MT, Prather KLJ, Thompson JR. 2019. Engineered microbial biofuel production and recovery under supercritical carbon dioxide. Nat Commun 10:587.

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