Novel Enzyme Boosts Production of Hydrocarbons From Feedstocks, Holds Key to Sustainable Aviation Fuels

Aviation is considered one of the most significant contributors to carbon dioxide emissions, and reducing its impact on the environment is achieved by using sustainable alternatives to traditional fossil fuels. Biofuels produced from plant oils have been explored as a potential alternative, but they also come with an expensive and inefficient production process.

Renewable Hydrocarbons for Aviation

Scientists from the Brazilian National Center for Research in Energy and Materials (CNPEM) conducted a study to improve the sustainable production of biofuels from renewable sources. After three and a half years of investigation, they identified an enzyme that can substitute the traditional catalysts used in thermochemical routes for producing aviation biokerosene.

Led by Brazilian Biorenewables National Laboratory (LNBR) head Letícia Zanphorlin, the team discovered the enzyme OleTPRN, a kind of polyunsaturated alkene-producing decarboxylase which belongs to the superfamily of cytochrome P450. The metalloenzyme was obtained from the bacteria species Rothia nasturtium. It shows potential in developing new biotechnological routes for producing sustainable hydrocarbons for aviation. These hydrocarbons are derived from various feedstocks like oleaginous biomass from soy, corn, and macaw palm and lignocellulosis biomass from straw, paper, and sugarcane bagasse.

Unlike the conventional catalysts, the new enzyme decarboxylates fatty acids with significant yields and is selective for various sizes and types of carbon chains. The process promotes deoxygenation, the trickiest part of generating sustainable aviation fuel.

Oxygen can damage the parts and engines of aircraft. According to Zanphorlin, biofuels like biodiesel and ethanol that are already mass-produced in Brazil are not used in the aviation industry, thus, the demand for new biocatalysts. Conventional catalysts in producing aviation fuel involve metals like nickel, palladium, cobalt, and platinum.

The metallic catalysts must be subjected to severe conditions, such as high temperature and pressure, to conduct the deoxygenation reaction. The process can harm the environment and produce technological waste, which could lead to financial losses.

Zanphorlin and her team evaluated teach amino acid's position in the enzyme's atomic structure and recorded its intermolecular interactions with fatty acids. The researchers noted that the results demonstrated all the possible applications of the discovery.

To implement the novel technology, biofuel production facilities should be adapted, but the distribution infrastructure used by traditional fuels can be shared by renewable sources that will act as drop-in fuels. These will serve as alternatives for petroleum-derived hydrocarbons without requiring the adaptation of fuel systems, engines, or distribution networks.

Role of Catalyst in Biofuel Production

The concerns about the depletion of fossil fuels have increased the awareness to look for alternative sources for fuel production. Over recent years, the production of biofuels has shown great promise as a substitute for petro-diesel fuel.

In producing biofuels, transesterification is used where oil or fat reacts with alcohol in the presence of a catalyst to form alkyl ester and glycerol. Catalysts refer to a substance that increases the rate of a chemical reaction without undergoing permanent chemical change. Three categories of catalysts are used in producing biofuels: acids, alkalis, and enzymes.

Free enzyme catalysts offer many advantages over chemical catalysts in biological catalyst systems. Enzymes naturally comply with all the principles of green chemistry due to their biological origin, biodegradability, and specific mode of action.