Algae as microscopic biorefineries

Some raw materials are limited and not available and recoverable all over the world – as we are now becoming acutely aware through the example of fossil fuels and rising energy prices. Renewable raw materials will therefore play an increasingly important role in the future as an energy source, but ideally also as a supplier of building blocks for more environmentally friendly chemicals and materials.

To use renewable raw materials, such as vegetable oils, for the production of chemicals, they must first be processed and in some cases chemically converted. In industry, this process is commonly referred to as refining. Until now, complex processes were required to extract and separate the biofeedstocks from the cells in which they were produced before the materials could be upgraded and further processed.

Expanding the natural machinery of cells

PhD researcher Natalie Schunck and Professor Stefan Mecking from the Chemistry Department of the University of Konstanz have now found a way to make the step towards upgrading sustainable raw materials much more efficient. They succeeded in introducing suitable synthetic catalysts, substances that trigger the desired upgrading reactions, into unicellular algae, especially at the place where they produce and store their lipids.

In their recent paper in Angewandte Chemie International Edition, the researchers describe how the catalysts were successfully transported to their destination. In addition, they provide evidence that the catalyst they use remains stable in the lipid storage compartments of the algal cells and fulfills the expected task there: the conversion of the unsaturated fatty acids of the algal cells into modified, long-chain building blocks suitable for the production of sustainable chemicals.

“By introducing the catalysts, we managed to add a chemical reaction to the algae machine that does not occur in nature, but is very relevant for the upgrading of oils and fats in the raw material processing industry – olefin metathesis. could thus be converted into small refineries,” says Mecking.

Binding Atmospheric Carbon Dioxide

The microalgae that Schunck chose are challenging, because they have a cell wall that must be overcome. To smuggle her catalyst to its destination, the researcher used a trick: She linked the catalyst to a dye normally used to color the lipid stores of algae cells. In this way she could ensure and also observe that the catalyst is reaching its target.

“Natalie Schunck succeeded in this very difficult experimental work because of her excellent research qualities. This project required extensive expertise in chemistry and a solid knowledge of biology, both of which she had acquired in her Life Science degree,” explains Mecking.

The decisive advantages of such algae are obvious: they are photo-autotrophic and use atmospheric carbon dioxide as a carbon source and sunlight as an energy source for the photosynthesis of complex chemical compounds, such as their fatty acids. This makes them promising candidates when it comes to finding renewable resource producers.

“By expanding the functional spectrum of algae, we are now one step closer to using it in the long term as a living microfactory for sustainable chemicals,” concludes Mecking.