This is a miracle! Scientists produce renewable jet fuel from common soil bacteria
Recently, a team of researchers at Lawrence Berkeley National Laboratory have successfully harvested alternative jet fuel from commonly found soil bacteria species belonging to the genus streptomyces.
In 1999, American Petroleum Institute (APA) published a report that suggests that the Earth’s oil reserves could dry anytime between 2062 and 2094. In contrast, a 2019 study from Stanford University’s Millennium Alliance for Humanity and the Biosphere (MAHB) predicts that the world will run out of oil much sooner i.e. in 2054. Imagine a world in which planes don’t fly, jets don’t protect the national borders, goods don’t get shipped, and rockets cannot leave Earth because there is no oil.
Since the global aviation, shipping, and aerospace industries run on oil, its depletion could lead to worldwide chaos. Forget depletion; the oil shortage is already causing an unprecedented increase in fuel prices across the globe. Recently, gas prices in the various states of the US crossed the mark of $5 a gallon, a new all-time high.
This is why many industries and scientists are constantly looking for renewable energy sources that could serve as alternatives to fossil fuels, especially oil (as it is likely to end foremost). An important step taken in this direction is the bacteria-driven production of renewable jet fuel by scientists at the Lawrence lab.
How did scientists produce jet fuel from streptomyces?
When fossil fuels like aviation kerosene (fuel used in jets and airplanes), petrol, or diesel are burnt, energy is produced in large amounts, and this energy powers a vehicle's engine. One of the many problems with fossil fuels is that it takes millions of years to form beneath the Earth's surface. The research team at Berkley was trying to create a fuel for which they don’t have to wait for millions of years to form again.
At that time, Jay Keasling, a professor of chemical engineering at the University of California, connected with researcher Pablo Cruz Morales (lead author of the study and project scientist at Lawrence lab) and asked him if he and his team could produce a molecule named Jawsamycin. Pablo had previously worked with streptomyces bacteria, so he knew that Jawsamycin is a molecule naturally produced due to the metabolic reactions in the body of streptomyces bacteria.
Keasling told Pablo that the molecule has the potential to release enormous amounts of energy, and “it's gonna be an explosive idea.” Listening to this, Pablo and his team started working on the idea. They engineered the Streptomyces coelicolor bacteria in a culture broth with sugars, salts, and some amino acids. Then, they harvested the bacteria, broke them, and separated the oily fractions (containing molecules similar to Jawsamycin) produced in their body. Finally, they decided to esterify the oils and a new kind of biofuel was ready.
The lab synthesized molecules that function similarly to Jawsamycin are referred to as “fuelimycin” by Pablo and his colleagues. When asked about the advantages and disadvantages of their biofuel over conventional fuel, Pablo told IE, “our fuel can be made using renewable processes, while the traditional fuels are derived from petroleum. The POP-FAMEs (Ours) can store more energy too so they may be more efficient if produced at scale.”
He further added, “the disadvantage is that we still need to develop a large-scale production method that is economically viable, and it's hard to compete with fossil fuels as they are subsidized, and the global economy is built around them. But this will change, the climate of our planet is changing and we need to stop using fossil fuels to slow down this process.”
The powerful chemistry of fuelimycin
Natural Jawsamycin is a molecule that is produced in the body of streptomyces when the bacteria feeds on sugar or amino acids and then converts those into molecules made of cyclopropane rings (triangular-shaped three carbon rings) during digestion. According to the researchers, the process of Jawsamycin formation is similar to how fat is formed in the human body. Still, it is the high-energy cyclopropane rings that make the difference.
Fat is formed as a result of the accumulation of excessive glucose (a six-carbon molecule) in the body as glycogen. Compared to six carbon molecules, triangular-shaped three-carbon molecules demand more energy for their formation. Explaining this further, Pablo wrote, “If you have bonds that are at a normal angle, an open chain of carbons, the carbons can be flexible and they get comfortable. 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.”
The construction of Jawsamycin and fuelimycin molecules is facilitated by an enzyme called polyketide synthases. Polyketide synthases are multi-enzymatic complexes that resemble fatty acid synthases that produce oily compounds in the bodies of humans and many other organisms. During their study, the researchers realized that the action of polyketide synthases enzyme forms the high-energy cyclopropane ring.
They believe that their biofuel could power jets, airplanes, and even rocket fuel in the future, but to make this possible, more research is required. When asked about their future plans related to their biofuel study, Pablo said, “The next steps are to make the bacteria produce more of this product and further modify the product so that it can be used for a wider range of applications such as shipping, rocketry, and aeronautics.”
The study is published in the journal Joule.
Freeing the global economy from its dependance on petroleum is key to slow down the pace of climate change. Energy-demanding applications like rocketry, aviation, and shipping are fueled with petroleum-derived hydrocarbons that are difficult to replace. These fuels are rich in cyclic molecules with strained bond angles allowing them to store more energy than non-cyclic molecules. The highest amount of energy can be stored in cyclopropanes, but these molecules are hard to produce via organic synthesis.
We produced polycyclopropanated fatty acid methyl ester (POP-FAME) fuels in bacteria. The POP-FAMEs can have energy densities of more than 50 MJ/L, which is larger than the energy of the most widely used rocket and aviation fuels. Although the next step is to scale up their production until the process is commercially viable, the availability of a biobased production method opens the possibility to replace fossil fuels in a very constrained sector.
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