Microbes to make new rocket fuel say it has ‘higher energy density than any petroleum product’

  Since 1903, humans have used rocket-propelled vehicles to explore the universe. With the continuous development of modern technology, human beings are no longer satisfied with near-earth exploration. China, the United States and other major countries have successively announced plans for deep space exploration.
  From near-earth exploration to deep space exploration, the flight speed and range of rockets need to be improved accordingly. Therefore, the design and preparation of high-energy-density fuels has received more and more attention from researchers at home and abroad.
  It is understood that under the condition of a certain volume of the aircraft, the higher the fuel density, the more fuel it can carry; and the higher the calorific value of combustion, the greater the energy provided by the unit volume of fuel, which is more beneficial for improving the performance of the aircraft.
  Recently, the Lawrence Berkeley National Laboratory of the U.S. Department of Energy announced the development of a new energy-intensive biofuel. The fuel is powerful enough to launch rockets, they say, and the biofuel is expected to have a higher energy density than any petroleum product, including leading aviation and rocket fuels JetA and RP-1.
  These fuel candidate molecules, known as polycyclopropane fatty acid methyl esters, derive their surprising energy potential from the basic chemistry of the structure.
  Polycyclopropane molecules contain multiple triangular three-carbon rings that make each carbon-carbon bond form a sharp 60-degree angle. The potential energy in this tension bond translates into more combustion energy than the larger ring structures or carbon-carbon chains commonly found in fuels. In addition, these structures keep fuel molecules tightly packed together in a small volume, increasing the mass of the fuel in any given tank, thereby increasing the overall energy.
  The project is led by synthetic biology pioneer Jay Keasling, CEO of the Department of Energy’s Joint Bioenergy Institute, and his team is led by JBEI (Office of Scientific Bioenergy Research Center) and ABPDU (Advanced Biofuel Process Demonstration Unit – Lawrence Berkeley National Laboratory) scientists.
  Jay Keasling, who has long been interested in the cyclopropane molecule, discovered that both currently known organic compounds with three carbon rings are naturally metabolized by Streptomyces sp.
  The team studied jasalomycin, one of the two organic compounds above. Discovered in 1990, palatine is so named because its unprecedented five cyclopropane rings give it the appearance of a jaw full of fangs.
  They studied the genes in the original strain that encode the enzyme that builds jalatomycin, as well as the genome of the related Streptomyces sp., hoping to remix existing bacterial machinery to create a new molecule with the properties of an instantly combustible fuel.
  They then found in the original strain that the enzyme responsible for building these high-energy cyclopropane molecules was polyketide synthase, which assembles all the necessary components to make polycyclopropane fatty acid methyl esters.
  The fatty acid produced by engineered Streptomyces contains up to seven cyclopropane ring chains on a carbon backbone, and is called fuelomycin, on top of which it can be used as a fuel with only one additional chemical processing step.
  The researchers also evaluated the energy density of the biofuel.
  On the one hand, polycyclopropane fatty acid methyl esters were analyzed using NMR spectroscopy, demonstrating the presence of the elusive cyclopropane ring; on the other hand, computer simulations were used to compare the performance of these compounds with conventional fuels.
  Simulation data show that the biofuel is safe and stable at room temperature, and its energy density value will exceed 50 megajoules per liter. Regular gasoline is 32 megajoules per liter, the most common jet fuel JetA and the popular kerosene-based rocket fuel RP1 are around 35 megajoules.
  Next, the optimization for polycyclopropane fatty acid methyl esters is divided into two directions.
  One is to help the biofuel further “offload” by removing two oxygen atoms from each molecule. Oxygen atoms add weight but no combustion benefit, and proper deoxygenation can further optimize PAFA.
  Second, efforts are made to increase bacterial production efficiency to produce sufficient fire tests. At present, the productivity of engineered Streptomyces species is limited to produce sufficient quantities of polycyclopropane fatty acid methyl esters. 10kg of fuel to test in a real rocket engine. The team is investigating how to modify the multienzyme production pathway to generate polycyclopropanated molecules of different lengths. Long chains of solid fuels will be used as some rocket fuels, short chains may be better for jet fuel, and the middle ones may be diesel replacement molecules.
  In addition to the ultra-high energy density, another advantage of this biofuel that cannot be ignored is its ecological advantages during production and use.
  In traditional production, this type of fuel can only be prepared from petroleum using a highly toxic synthesis process. Polycyclopropane fatty acid methyl esters are produced by bacteria that feed on plant matter, often from inedible agricultural residues and bushes removed to prevent wildfires. Compared to oil-based fuels, the use of these will significantly reduce the amount of greenhouse gases produced.

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