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Rotten gold?

Over the next three years, a project run from Denmark will investigate how to create value based on a foul-smelling nuisance on beaches: rotting seaweed. It turns out that seaweed is home to a small worm which may be of great value for fish farming if the optimal living conditions for the worm can be identified. The project recently received a DKK 2.3 million (EUR 0.3 million) grant from the Danish Council for Independent Research - Technology and Production Sciences.

Let’s put our cards on the table. This article is about something that may seem quite distant to many people: rotten seaweed. But while many of us steer clear of the strip of stinking seaweed on the beach, finding it a source of annoyance, for biologist Martin Holmstrup seaweed has become the basis of a project that may provide all of us with sufficient sustainable food in the future. You might say that this is a story of finding gold in dirt if you just look more closely.

The smelly nuisance is in fact a biosphere where the Enchytraeus albidus worm - also known as the white worm - lives. This small worm may prove to be a sustainable solution for one of the world's fastest growing industries: fish farming.

In Denmark, there is a great potential to boost exports of fish, but this requires access to sustainable high-protein feed for the fish. And this is where the challenge lies. The demand for protein-rich food is increasing as the world’s population grows. And food should not have the same high CO2footprint as in animal production, for example. Fish are a promising alternative, and currently, almost half of the fish consumed derives from fish farms. However, conventional animal feed for fish farming is not readily accessible, and alternative feed, such as insects, requires relatively comprehensive and costly production facilities.

"Insects are not optimal fish feed, because they don’t contain as much omega3 fatty acids as we would like," explains Martin Holmstrup. "So there’s a great interest worldwide to find promising alternatives. This is where the small white worm enters the picture."

An obvious idea

The white worm became the centre of attention because of Martin Holmstrup’s academic background. One of his usual areas of research is how animals survive cold weather, and the white worm, with its special physiology, caught the biologist's attention.

The worm can grow up to 4 cm long, and is found in huge numbers in nature, if you dig just a little into rotten seaweed on the beach, for example. The worm has a special survival mechanism that allows it to withstand being frozen: it develops high levels of long-chain omega3 fatty acid in its cell membranes in order to survive cold temperatures. This makes it ideal for fish feed, as fish feed has to contain as much omega3 fat as possible.

The Production of high quality fish feed from enchytreaid biomass project will run for three years, and the aim is to find the optimal conditions to breed and produce feed from the worm. The project will be carried out in collaboration with the Danish companies Aller Aqua A/S, and Fishlab - Venøsund Fisk og Skaldyr ApS.

The research will be conducted under the CBIO research centre at Aarhus University. CIBO works to develop new branches within the circular bioeconomy, for example manufacturing new high-value substances from innovative utilisation of by-products as a means of avoiding waste. Therefore, another aim of the project is to investigate whether other residual products can be used to breed the worms.

"Everybody will win if we succeed. First of all, we’ll be removing a waste product in the form of rotten seaweed, and we’ll be creating a product for an industry engaged in providing new food resources, thereby benefitting society. In the longer term, it may also turn out that the waste from juice or beer production, for example, can be used as a medium for breeding worms. In this way, waste such as seaweed or residual products such as pulp can be turned into products in an extended value chain. Now, together with our partners, we’re looking forward to exploring and developing this approach to protein feed for fish farming, and we hope to find new approaches to creating new value,” explains Martin Holmstrup.

Professor Martin Holmstrup,
Department of Bioscience.
Email: martin.holmstrup@bios.au.dk
Mobile: +45 3018 3152

Read more about the Centre for Circular Bioeconomy (CBIO) here.