The blue-green sustainable proteins of seaweed

… may soon be on your plate.

The protein in sea lettuce, a type of seaweed, is a promising complement to both meat and other current alternative protein sources. Seaweed also contains many other important nutrients, and is grown without needing to be watered, fertilised or sprayed with insecticides. However, the proteins are often tightly bound, and their full potential has not yet been realised on our plates.  But now researchers at Chalmers University of Technology, in Sweden, have found a new way to extract these proteins three times more efficiently than before – and this progress paves the way for seaweed burgers and protein smoothies from the sea.

“It tastes like umami with a certain salty flavour, despite not containing such high levels of salt. I would say it’s a great flavour enhancer for seafood dishes and products, but the possibilities to explore are endless. Why not protein smoothies or ‘blue burgers’ from the sea?” says João Trigo, PhD in Food Science at Chalmers, about the dark green powder, which is a concentrate of proteins from sea lettuce, scientifically known as Ulva fenestrata. Sea lettuce is a type of macroalgae, commonly called seaweed, which grows on rocks in calm waters, or free-floating on the surface, and resembles ordinary lettuce leaves in appearance.

The so-called protein shift – switching from red meat to more sustainable and healthy protein sources – is a way to reduce the climate impact of food production while providing everyone with a nutritious diet. Many alternative protein sources, mainly based on pea, soy and mushroom, are common in our grocery stores. But all the vegetarian protein that is found under the sea is still an untapped source.

The CirkAlg-project, led by Chalmers University of Technology, has explored the possibilities of developing processes that can create a new, “blue-green” food industry in Sweden, and make use of seaweed as a promising source of protein. Within the framework of the project, a newly published scientific study shows a unique way of extracting proteins from sea lettuce, so that it is now possible to extract three times more protein from the seaweed than was possible with previous methods.

“Our method is an important breakthrough, as it brings us closer to making it more affordable to extract these proteins, something that is done with pea and soy proteins today,” says João Trigo.

Contains several essential nutrients

In addition to essential proteins, sea lettuce contains several other substances of great nutritional value for humans, such as vitamin B12 and the same kind of omega-3 fatty acids found in oily fish, like salmon. People who do not eat animal products are at risk of developing a deficiency of vitamin B12, which is necessary for the body to form red blood cells, among other things. And the cultivation of sea lettuce has several advantages compared to land-growing proteins – such as the fact that the seaweed does not need to be watered, fertilised or sprayed with insecticides. Sea lettuce is also hardy and grows well under many different conditions, such as different salinity and access to nitrogen.

“Humanity will need to find and combine the intake of many more diversified protein sources than we have available in our diet today, to meet sustainability and nutritional requirements. Algae is a good addition to many of the products already on the market. We need all these solutions and so far, the sea-based possibilities, the so-called blue proteins, have been overlooked,” says Ingrid Undeland, Professor of Food Science at Chalmers and coordinator of CirkAlg.

In addition to the newly published extraction method, the Chalmers researchers are working together with the University of Gothenburg to increase the actual protein content in the seaweed. By cultivating sea lettuce in process water from the seafood industry, the protein content can be increased significantly, while nutrients that would otherwise be lost are circulated back into the food chain. At Tjärnö Marine Laboratory (part of the University of Gothenburg) in northern Bohuslän in Sweden, a large number of successful cultivation experiments have been carried out within the CirkAlg-project, based on industrial water side currents.

“In the future, we also want to be able to make use of the parts of the algae that are not proteins, and that could be used in food, materials or for medical applications. The goal is that no molecules should go to waste, to achieve both sustainability and commercial opportunities,” says Ingrid Undeland.

More about the extraction method

In addition to proteins that are water-soluble, sea lettuce also contains plenty of fat-soluble so-called membrane proteins. This means that the seaweed proteins are more complex to extract than, for example, soy and pea protein. In a first-step of the new process, the cell membranes of the sea lettuce are opened up in order to access the fat-soluble proteins. The different types of proteins are then extracted with water adjusted to a high pH, and in the next step, by making the solution acidic, the proteins are precipitated into aggregates that could then be separated from the water and utilised as a protein-rich ingredient. It was also seen that the marine omega-3 fatty acids were enriched in the protein ingredient, and a follow-up study confirmed that the same was true for vitamin B12. The new algae protein ingredient can thus help meet a wider range of nutritional needs compared to soy protein.

The study) A new method for protein extraction from sea lettuce (Ulva fenestrata) via surfactants and alkaline aqueous solutions was published in Food Chemistry. The study’s authors are João Trigo, Sophie Steinhagen, Kristoffer Stedt, Annika Krona, Simone Verhagen, Henrik Pavia, Mehdi Abdollahi and Ingrid Undeland. At the time of the study, the researchers were active at Chalmers University of Technology, the University of Gothenburg and RISE – Research Institutes of Sweden.

For more information, please contact:

Ingrid Undeland, Professor, Division of Food and Nutrition Science, Department of Life Sciences, Chalmers University of Technology, +46 737 08 08 64, undeland@chalmers.se

João Trigo, PhD, Division of Food and Nutrition Science, Department of Life Sciences, Chalmers University of Technology, +46 739 78 74 16  trigo@chalmers.se

Ingrid Undeland speaks English and Swedish, João Trigo speaks English and Portuguese. They can be available for live and pre-recorded interviews. At Chalmers, we have podcast studios and film equipment on site and can assist with requests for TV, radio or podcast interviews.

Footage from seaweed being cultivated and harvested at Tjärnö Marine Laboratory in northern Bohuslän in Sweden can be downloaded here. 
Credit all footage: Chalmers | Lars Lanhed

Caption: Proteins from seaweed, such as sea lettuce, have the potential to become an important food component. However, the proteins are often tightly bound, but now researchers at Chalmers University of Technology, in Sweden, have found a new way to extract these proteins three times more efficiently than before. Here, sea lettuce is grown in tanks containing water that was previously used in the seafood industry. Through this cultivation, they take up nutrients that would otherwise have been discarded.
Credit: Sophie Steinhagen

Journal: Food Chemistry
DOI: 10.1016/j.foodchem.2024.141839
Method of Research: Experimental study
Subject of Research: Not applicable
Article Title: A new method for protein extraction from sea lettuce (Ulva fenestrata) via surfactants and alkaline aqueous solutions
Article Publication Date: 13-Nov-2024
COI Statement: The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: João P. Trigo, Ingrid Undeland, and Mehdi Abdollahi have a patent pending to Chalmers Ventures AB as a result of the work described in this article. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Media Contact

Karin Wik
Chalmers University of Technology
karin.wik@chalmers.se