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Producing chemicals sustainably using microalgae

Many chemicals in lubricants and washing powder are produced from fossil fuel. However, as fossil fuel is limited and reserves are slowly but surely running out, finding suitable substitutes is essential. This is the only way to ensure that much needed working materials continue to be available in the future. Sandra Heß from the University of Konstanz is involved in an interdisciplinary PhD project that explores the production of plastics, lubricants and surfactants from algal oil.

The Department of Chemical Materials Science at the University of Konstanz has been researching renewable raw materials for many years. The researchers initially focused on vegetable oils produced from rapeseeds and sunflower seeds. Such oils have many unsaturated fatty acids that contain valuable double bonds. Using isomerisation-alkcoxycarbonylation, these fatty acids can be converted into linear di-esters that can be used along with a diol to produce a new fossil-oil-free plastic.

Unfortunately however, the production of rapeseed and sunflower oils requires agricultural land, which can often be in direct competition with food production. The researchers from Konstanz therefore decided to test whether isomerisation-alkcoxycarbonylation can also be applied to algal oil. To carry out the project, they decided to join forces with researchers from the Department of Ecophysiology. The major advantages of algal oil are that algae cultivation does not rely on agricultural land, there is less variation in annual cycles, and algae can grow very well in saltwater, so no freshwater is required. Algae also produce unique fatty acids that plants do not have.

Breaking up algae cells with ultrasound

Sandra Heß’ PhD thesis addresses the conversion of algae oil into usable chemicals. © Friederike Schütze

The algae studied at the University of Konstanz are frugal single-celled organisms. They carry out photosynthesis, meaning that algae cultivation also contributes to CO2 fixation. In addition, algal cells have a third more fat than rapeseed, which considerably increases their productivity. "Light, carbon dioxide and saltwater are all that is needed to cultivate algae," says Sandra Heß whose PhD project is specifically focused on algae, in particular on the marine microalgal species Phaeodactylum tricornutum which has a particularly high lipid content and rapid growth. Ph. tricornutum can be modified by changing simple parameters such as light conditions, temperature and salt content so that the cells have optimal fatty acid composition for the crude oil production.

The fatty acid compounds are harvested by centrifugation. In order to access the lipids in the cells, the algal cells are broken up using ultrasound and the algal oil is extracted with organic solvents. Algal oil not only contains lipids and fatty acids, but also chlorophyll, which explains the green colour of the newly discovered raw material. The resulting oil can be used for a broad range of different purposes.

Interdisciplinary research opens up new possibilities

The characteristic green colour of algae oil comes from chlorophyll. © Sandra Heß

Most research efforts so far have concentrated on finding out whether algal oil is suitable for the production of plastics. However, it can be used for much more than just this. "In my PhD project, I am trying to find out whether and how specific chemical reactions can expand the applicability of fatty acids," says Sandra Heß. The possibilities seem almost infinite, ranging from the production of surfactants to that of lubricants and dyes, all of which are currently made using fossil oil. Since fossil oil will one day run out, it is crucial to look for alternatives before this happens. The unique fatty acid structures of algae also make it possible to produce completely new compounds.

The Faculties of Chemistry and Biology at the University of Konstanz are therefore working closely together in order to deliver efficient results. The biologists cultivate the algae and they also carry out experiments to determine the optimal light and temperature conditions for algal growth. In addition, they develop genetically modified algal strains that produce higher than normal amounts of lipids. The chemists deal with harvesting and extracting the sought-after compounds as well as improving and modifying the processes by way of chemical reactions.

"I obtained my life sciences master's degree at the University of Konstanz. I therefore have good insights into both areas, and can focus on both the chemical and biological aspects, depending on what I am studying," says Sandra Heß, describing her way of working. The cooperation with researchers from different disciplines allows the young researcher to approach the matter from different angles, which is very positive for her work. "The possibilities with regard to the new raw material are endless. This is why I think that the topic of my PhD thesis is so beautiful and so diverse," says the PhD student with great enthusiasm.

A raw material for the future

The microalga Phaeodactylum tricornutum is a single-celled organism with a particularly high proportion of lipids. The dark-grey circled areas mark the fat droplets in the alga. © Sandra Heß

Research has shown that the composition of algal oil is unique. In contrast to other oils such as sunflower or rapeseed oil, algal oil contains fatty acid structures that are particularly suitable for producing high-quality chemical intermediates.

Microalgal oil yields are not yet comparable with those of fossil fuel. However, products like algal oil are becoming important alternatives to fossil oil in view of dwindling fossil fuel reserves . "Of course, we are working on making the production of algal oil more efficient, but we cannot replace fossil oil overnight. We are only at the start of the journey in terms of producing and using this renewable resource," concludes Sandra Heß.

Sandra Heß took her final school exams at the Mathilde-Weber School in Tübingen in 2008 and was awarded the 2008 MTZ®-BIOPRO Student Prize for her outstanding results.

The MTZ®-BIOPRO Student Prize is awarded jointly by the MTZ® Foundation and BIOPRO Baden-Württemberg to the best graduates at Baden-Württemberg grammar schools with a special focus on biotechnology.

 

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