Algae as Microscopic Biorefineries

by University of Konstanz

Via microalgal biorefineries, renewable raw materials may play an increasingly important role in the future as energy sources, and ideally also as building blocks for more environmentally compatible chemicals and materials.

To use renewable raw materials, such as plant oils, to produce chemicals, they must first be processed and in some cases chemically converted. This process is commonly referred to as refining. Up to now, complex processes were required to extract and separate the bio-raw materials from the cells in which they were produced before the materials could be upgraded and further processed.

Expanding the natural machinery of cells

Doctoral researcher Natalie Schunck and Professor Stefan Mecking from the Department of Chemistry at the University of Konstanz have now found a way to make the step of upgrading sustainable raw materials much more efficient. They succeeded in introducing suitable synthetic catalysts — substances that bring about the desired upgrading reactions — into unicellular algae. Specifically, they are introduced at the site where the microalgae 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 used remained stable in the lipid storage compartments of the algae cells and fulfilled the anticipated task there. The task: conversion of the unsaturated fatty acids of the algae cells into modified, long-chain building blocks suitable for producing sustainable chemicals.

“By introducing the catalysts, we managed to add a chemical reaction to the algae’s machinery that does not occur in nature but is highly relevant to the upgrading of oils and fats in the feedstock processing industry — olefin metathesis. The algae cells could thus be turned into tiny refineries,” says Dr. Mecking.

Binding atmospheric carbon dioxide

The microalgae Ms. Schunck chose are challenging, because they possess a cell wall that needs to be overcome. To “smuggle” her catalyst to its destination, the researcher used a trick: She coupled the catalyst to a dye normally used to stain the lipid stores of algal cells. In this way she was able to ensure, and observe, that the catalyst reached its target.

The advantages of such algae are obvious: They are photoautotrophic, using 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 a step closer to using them in the long-term as living microfactories for sustainable chemicals,” Dr. Mecking said.