How a bacterial enzyme could revolutionize aviation biofuels

The study, which was published in Proceedings of the National Academy of Sciences (PNAS), was conducted by scientists from the Brazilian Biorenewables National Laboratory (LNBR) at the Brazilian National Center for Research in Energy and Materials (CNPEM)

The researchers also revealed the molecular mechanisms involved in the enzyme’s action using synchrotron light, a type of high-flux high-brightness electromagnetic radiation that can show the three-dimensional structure of protein crystals.

The researchers analyzed the position of every amino acid in the enzyme’s atomic structure and mapped its intermolecular interactions with fatty acids. This helped them understand all the possible applications of the discovery.

The researchers also said that they identified an enzyme that can replace the traditional catalysts used in thermochemical routes for the production of aviation biokerosene after three and a half years of research.

Sustainable biofuels

The discovery could enhance the production of sustainable biofuels for aviation and maritime shipping from different sources, such as oleaginous biomass from soy, macaw palm, or corn, among others, and lignocellulosic biomass from sugarcane bagasse or straw and in the paper industry.

Along with this laboratory investigation, other teams at CNPEM worked on patent filings and on technical, economic and environmental analysis of the biological routes, the results of which will be published soon.

The researchers applied for a patent on the enzyme in 2021. They said that one of CNPEM’s key advantages is that they can develop a technological solution, implement a pilot project, ramp it up to an industrial scale, and perform the technical, economic and environmental assessments needed to detect any potential improvements in the innovation as it’s being developed.

The enzyme could open up new possibilities for making biofuels for airplanes. According to the researchers, Brazil produces about 150 million metric tons of waste from sugarcane every year. This is a type of lignocellulosic material that can be converted into biofuels. They said that this amount could be increased without harming the environment.

To use this technology, biofuel plants would need some changes, but they could use the same distribution system as fossil fuels. These biofuels would act as “drop-in” fuels, which means they can replace petroleum-based fuels without changing engines, fuel systems or distribution networks.

The researchers also said that this enzyme could be used in many other industries. It can make alkenes, which are chemicals that are used to make most of the products in the chemical industry, such as polymers and plastics. Alkenes are also important for the food, cosmetics, pharmaceutical, and transportation industries.

The study, which was published in Proceedings of the National Academy of Sciences (PNAS)

Study abstract:

The enzymatic decarboxylation of fatty acids (FAs) represents an advance toward the development of biological routes to produce drop-in hydrocarbons. The current mechanism for the P450-catalyzed decarboxylation has been largely established from the bacterial cytochrome P450 OleTJE. Herein, we describe OleTPRN, a poly-unsaturated alkene-producing decarboxylase that outrivals the functional properties of the model enzyme and exploits a distinct molecular mechanism for substrate binding and chemoselectivity. In addition to the high conversion rates into alkenes from a broad range of saturated FAs without dependence on high salt concentrations, OleTPRN can also efficiently produce alkenes from unsaturated (oleic and linoleic) acids, the most abundant FAs found in nature. OleTPRN performs carbon–carbon cleavage by a catalytic itinerary that involves hydrogen-atom transfer by the heme-ferryl intermediate Compound I and features a hydrophobic cradle at the distal region of the substrate-binding pocket, not found in OleTJE, which is proposed to play a role in the productive binding of long-chain FAs and favors the rapid release of products from the metabolism of short-chain FAs. Moreover, it is shown that the dimeric configuration of OleTPRN is involved in the stabilization of the A-A’ helical motif, a second-coordination sphere of the substrate, which contributes to the proper accommodation of the aliphatic tail in the distal and medial active-site pocket. These findings provide an alternative molecular mechanism for alkene production by P450 peroxygenases, creating new opportunities for biological production of renewable hydrocarbons.