Ekstraher med Jawsamycin

Når disse bakterier fødes, skaber de et mærkeligt molekyle, der kan bruges til at lave flybrændstof

Ekstraher med Jawsamycin. Kredit: Pablo Morales-Cruz

Fly er afgørende i moderne tid til at transportere mennesker, levere varer og udføre militære operationer, men de petroleumsbaserede brændstoffer, der driver dem, er knappe. Forskere har nu opdaget en måde at skabe et alternativt jetbrændstof ved at høste et usædvanligt kulstofmolekyle produceret af den metaboliske proces af bakterier, der almindeligvis findes i jorden. Forskning udført af forskere ved Lawrence Berkeley Lab blev for nylig offentliggjort i tidsskriftet joule.

“I kemien frigiver alt, der kræver energi for at få det, energi, når det går i stykker,” siger hovedforfatter Pablo Cruz-Morales, mikrobiolog ved DTU Biosustain, en del af Danmarks Tekniske Universitet. Når petroleum jetbrændstof antændes, frigiver det en enorm mængde energi. Forskere ved Lawrence Berkeley Laboratory’s Keasling Lab mente, at der må være en måde at kopiere dette på uden at skulle vente millioner af år på, at nye fossile brændstoffer dannes.

En eksplosiv idé

For at se, om han kunne syntetisere et vanskeligt molekyle, der har potentialet til at producere masser af energi, Jay Keasling, en kemiingeniør ved[{” attribute=””>University of California, Berkeley, approached Cruz-Morales, who was a postdoctoral researcher in his lab at the time. “Keasling told me: it’s gonna be an explosive idea,” says Cruz-Morales.

Common Bacteria Streptomyces

The common bacteria streptomyces which makes the cyclopropane-containing molecules. Credit: Pablo Morales-Cruz

Keasling wanted to recreate a molecule called Jawsamycin, which is named after the movie “Jaws” because of its bite-like indentations. It is generated by the common bacteria streptomyces, an organism that Cruz-Morales had worked with in the past.

“The recipe already exists in nature,” says Cruz-Morales. The jagged molecule is produced by native metabolism of the bacteria as they munch away on glucose. “As they eat sugar or amino acids, they break them down and convert them into building blocks for carbon-to-carbon bonds,” he says. “You make fat in your body in the same way, with the same chemistry, but this bacterial process has some very interesting twists.”

These twists, which give the molecules their explosive properties, are the incorporation of cyclopropane rings – rings of three carbon atoms arranged in a triangular shape. “If you have bonds that are at a normal angle, an open chain of carbons, the carbons can be flexible and they get comfortable,” explains Cruz-Morales. “Let’s say you make them into a ring of six carbons – they can still move and dance a little bit. But the triangle shape makes the bonds bend, and that tension requires energy to make.”

After careful analysis, the research team determined that the enzymes that were responsible for the construction of these high-energy cyclopropane molecules were polyketide synthases. “Polyketide synthases are the ultimate biological tool to make organic chemistry,” says Cruz-Morales.

Making Fuel With Biology

Cruz-Morales explains that the fuel produced by the bacteria would work a lot like biodiesel. It would need to be treated so that it could ignite at a lower temperature than the temperature needed to burn a fatty acid. However, when ignited, it would be powerful enough to send a rocket into space. “If we can make this fuel with biology there’s no excuses to make it with oil,” says Cruz-Morales.  “It opens the possibility of making it sustainable.”

In the future, Cruz-Morales hopes that he and the team of Department of Energy researchers who worked on the project will be able to scale up this process so that their alternative fuel could actually be used in aircraft. “The problem right now is that fossil fuels are subsidized,” says Cruz-Morales. “This is something that is not only related to the technology, but the geopolitical and socio-political constitution of the planet right now. You can see this as a preparation for the moment because we are going to run out of fossil fuels, and there’s going to be a point, not far from now, when we will need alternative solutions.”

Reference: “Biosynthesis of polycyclopropanated high energy biofuels” by Pablo Cruz-Morales, Kevin Yin, Alexander Landera, John R. Cort, Robert P. Young, Jennifer E. Kyle, Robert Bertrand, Anthony T. Iavarone, Suneil Acharya, Aidan Cowan, Yan Chen, Jennifer W. Gin, Corinne D. Scown, Christopher J. Petzold, Carolina Araujo-Barcelos, Eric Sundstrom, Anthe George, Yuzhong Liu, Sarah Klass, Alberto A. Nava and Jay D. Keasling, 30 June 2022, Joule.
DOI: 10.1016/j.joule.2022.05.011

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