Danish university researchers convert cooking oil into biofuel using rare algae enzyme

Researchers at Aarhus University in Denmark have discovered an unusual enzyme in microalgae that can be used to convert waste oils and fat into drop-in biofuels.

Supported by a grant of DKK 3 million (€0.4 million) from the Novo Nordisk Foundation, the research project at Aarhus University’s Department of Engineering aims to develop a system that converts organic waste into sustainable biofuels via natural processes.

The special light-dependent enzyme, which was first discovered around two years ago, exists in microalgae. It has the particular characteristic that, with light as the only source of energy, it can decarboxylate fatty acids into alkanes, and thereby synthesise biofuel.

"The project covers all stages of the process, from selection of the best mutant of the enzyme to development of the flow system itself, which, via photobiocatalysis, will convert organic waste oils and fats into different biofuels in a continuous flow," explained assistant professor Bekir Engin Eser.

The sustainable biofuel produced using this method can be used directly in existing engines, with petrol and diesel vehicles able to switch to run on the carbon-neutral green fuel.

Production has to be in a single, continuous flow in which waste stream is added at one end and, via enzymatic photobiocatalysis with the algae enzymes, is converted into fuel at the other end.

Numerous processes have to be linked together before the fuel is produced. Currently, the enzyme produces alkanes of different lengths; the goal is to develop variants of the enzyme through protein engineering, in order to adjust the individual production of alkanes to a kind of portfolio.

This is explained by associate professor Selin Kara, who is leading the project: "So far, no one has tried to specialise the enzyme to create the product portfolio we want. For this reason, part of this project is to build a mutation library of the enzyme, so that, using different systems, we can make either diesel, petrol or jet-fuel in one process.”

The research team plans to scale up the technology: "The system has to be very, very efficient, because enormous amounts have to be produced if we are to get industry interested in this transition," Kara added.