Production of synthetic polymers from algae oil

Algae are rich in valuable substances and can be grown easily, which makes them promising candidates for the sustainable production of raw materials. The work done by Prof. Dr. Stefan Mecking at the University of Konstanz in cooperation with plant physiologist Prof. Dr. Peter Kroth, confirms this. The two scientists have developed a method to transform algae oil into high-quality chemical raw materials which can, amongst other things, be used for the production of polymers. This opens up new possibilities for the use of algae as a raw material source beyond just a substitute for crude oil.

Algae are seen as a beacon of hope in the creation of a sustainable economy and they play an important role in virtually all areas of the bioeconomy. They can be used to produce a broad range of materials and products, including energy, food supplements or as a source for new medicines. What’s more, they are easy and quick to grow. “Like plants, algae cover their energy requirements with light and only need water and nutrient salts for growth,” explains Peter Kroth, Professor for Plant Ecophysiology at the University of Konstanz. Kroth’s research focuses on algae and their biotechnological application.

The advantages of algae for the bioeconomy are apparent: they do not need a large space in which to grow, they can be grown very quickly and efficiently and do not use land given over to agriculture, therefore they are not in competition with space needed for the production of food. In addition, algae oils have a much higher proportion of polyunsaturated fatty acids than conventional vegetable oils. This makes them attractive candidates for the sustainable supply of raw materials, an area that chemist Prof. Dr. Stefan Mecking from Konstanz is focused on.The idea is not just to use algae as a substitute for crude oil, but to transform them into high-quality chemical constituents for use as chemical raw materials. “We want to preserve the unique molecular structure of renewable raw materials using new catalytic methods. This helps us produce high-quality components directly without having to first make oil-like intermediaries,” says Kroth, explaining the principle of the method. The doctoral students who participated in the research project managed to do just this using a new method that enabled them to transform algae oil into chemical raw materials that can then be used to produce polymers and other materials.

A “dream reaction” leads to functional chemical components

The chemists from Konstanz succeeded in transforming algae oil into high-quality chemical raw materials using a process called isomerizing alkoxycarbonylation. This is a reaction in which the unsaturated fatty acids are transformed into linear diesters in the presence of carbon monoxide, methanol and a catalyst. “This conversion is achieved through what is known as a ‘dream reaction’, during which a functional group from the centre of the algae molecule is transformed into a functional group somewhere else in the molecule,” says Mecking, explaining the highly accurate procedure. A functional group from the centre of the molecule is transformed into an ester group at the end of the molecule. The new molecule then has two functional groups at its ends. “Such molecules can be easily linked together to create polymers, which is why they are attractive components for the production of plastics,” explains Mecking.

The researchers used unicellular Phaeodactylum tricornutum algae for the pilot experiments. The algae oil has a high proportion of polyunsaturated fatty acids that can be genetically modified to produce larger amounts of lipid. “In principle, the synthesis can also be performed with oils from other algae. The efficiency of the reaction depends on the quantity of lipids that the algae produce as well as on the fatty acid composition,” says Kroth.

Following their initial success, the researchers are now going on to optimize the extraction method. They have found out that ultrasonic treatment of the oil proved advantageous in terms of increasing the quantity of oil. “We are still working on the optimal extraction of algae oil,” says Mecking who is also hoping to find a way to link the extraction of the oil with other catalytic reactions.

Renewable and degradable – alternatives to crude oil

Mecking’s research group has already produced polymers from synthetic diester molecules, which might in future be used as components for mechanically robust, but degradable materials. “In addition to using algae oil for the production of materials, it can also be used for the production of surface active substances or lubricants,” says Mecking. There are many other possibilities than diesters for recovering chemical materials and Mecking still has a great deal of options to test. “In the long term, I hope to produce long-chain molecules with one or several different functional groups,” says Mecking, referring to their future plans.

However, he believes that despite the successes so far achieved, more than one raw material source will be used to replicate crude oil. “I believe that there will be several different, complementary solutions to replace crude oil,” he says. And algae products could well be one such solution. They have special properties, such as the ability to produce oils with a high proportion of polyunsaturated fatty acids. But the researchers do not believe that they will be in a position to use algae to replace fossil fuels as energy providers in the foreseeable future. “The cultivation of algae and the production of algae oil is not yet energy efficient, despite the ability of algae to carry out photosynthesis. More energy is required to produce one litre of algae oil than the energy contained in a litre of the actual oil,” says Kroth, who is nevertheless optimistic and believes that new methods will be found to overcome this obstacle.

 

Photo: The team of chemists and biologists at the University of Konstanz reflected in a bioreactor in which the algae are grown (from left to right): Julia Zimmerer, Philipp Roesle, Prof Dr. Peter G. Kroth, Angelika Eckert, Prof. Dr. Stefan Mecking, Florian Stempfle, Dr. Carolina Rio Bártulos, Sandra K. Heß (not on the photo: Dr. Bernard Lepetit). (© University of Konstanz)

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