12 May 2026
Turning waste into valuable oils using microorganisms
Replacing fossil-based industries with sustainable biomanufacturing is a key challenge in the transition to a circular economy. In her doctoral thesis at Luleå University of Technology, Eleni Krikigianni shows how microorganisms can be used to convert waste streams into biofuels and other valuable products.
“Some microorganisms have a natural ability to store large amounts of oil inside their cells, which makes them useful for bio-based production,” says Eleni Krikigianni.
Microorganisms as cell factories
In the thesis Bioconversion Potential of Oleaginous Microorganisms, she investigates how different microorganisms, including yeasts, microalgae and marine species named thraustochytrids, can be used to produce valuable microbial oils and other bioproducts. The focus is on how microbial physiology, feedstock selection and cultivation conditions affect growth performance and product biosynthesis.
The study includes both refined raw materials and waste-derived feedstocks, such as by-products from breweries, plant-based biomass and used cooking oil. These materials contain different carbon-rich compounds that influence how microorganisms grow, which makes the process more complex.
“By adjusting the process conditions and selecting the right microbial host, we can control how carbon is used inside the cell and influence which products are formed,” she explains.
Different pathways lead to different products
The results show that microorganism-specific pathways are activated when different feedstocks and cultivation strategies are used, leading to different types of fatty acids and bioproducts. Under some conditions, oils suitable for biodiesel are produced, while other setups favour specialised fatty acids for nutraceutical applications, or protein-rich biomass.
Marine microorganisms were particularly effective at producing omega-3 fatty acids and degrading oily substrates.
From waste streams to bio-based products
The work shows that different types of waste-derived feedstocks can be used in bioprocesses and by tuning the cultivation conditions according to the metabolism of the selected microbial host we can produce oil with biofuel or nutraceutical value, or nutritional microalgal protein in a sustainable way.
“The goal is to use renewable waste streams and convert them into higher-value products using targeted bioprocess design,” says Eleni Krikigianni.
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