Researchers at the Hamburg University of Technology are investigating new processes that use enzymes to gently extract complex carbohydrates and high-quality proteins from aquatic plants in order to produce new products for the feed and food market.
You know them from a walk on the beach: washed-up algae often line the transition from the water to the beach. Whether green or brown, the aquatic plants found there come in a wide variety of colors. Scientists also refer to them as macroalgae to emphasize the contrast to unicellular microalgae. At the Hamburg University of Technology, Dr. Ana Malvis Romero and her project partners have been taking a very close look at various algae for three years: “Macroalgae are fantastic – they are full of valuable ingredients such as proteins and carbohydrates,” says the researcher. She has been working at the Institute for Technical Biocatalysis since 2020 and took over the leadership of the project “Novel products from marine resources”. Together with five students, she examined the potential of aquatic plants.
In the project, the scientists from the institute, led by Prof. Andreas Liese, and from the Institute for Environmental Engineering and Energy Economics, led by Prof. Martin Kaltschmitt, pursued a common goal: to identify particularly nutrient-rich types of algae and to develop an effective process for extracting the valuable ingredients. At the same time, the interdisciplinary approach helped the researchers to extract complex carbohydrates such as ulvan and alginate, as well as high-quality proteins, from the aquatic plants using different methods. Alginate is used in medicine to produce bandages because it can be used to make a gel that promotes wound healing. Ulvan can be used to enrich food.
Challenges in obtaining algae: from Rostock to Portugal
“We received our first algae samples from a company near Rostock that supported us as a partner from the very beginning. The employees collected the algae on the beach. But in the laboratory, we quickly realized that these plants were unsuitable for our investigations. The algae mass was mixed with mussels, for example,” explains Romero. So she looked for alternatives and found what she needed in Portugal after an internet search. She found a company that cultivates its algae under controlled conditions in water tanks in the countryside, exactly what they needed.
“This is a great advantage for our research. We source the algae directly from the manufacturer and know exactly which nutrients each type of algae contains from the product and ingredients information. This enabled me to order specific types of red, green and brown algae,” explains Romero. Each of these algae types differs not only in color but also in the concentration of its nutrients. “The red algae (Porphyra dioica) has a high protein content. The green algae (Ulva fenestrata) contains a high amount of ulvan and the brown algae (Phaeophyta Fucus vesiculosus) contains alginate – both valuable polysaccharides,” explains Ana Malvis Romero. Polysaccharides are complex carbohydrates that play an important role in the food market and in medicine.
In order to test the three selected types of algae under the same conditions in the laboratory, the algae first undergo a so-called pretreatment. It's a bit like processing plants in the kitchen – Romero uses powerful equipment that resembles kitchen utensils: “We get the algae delivered from Portugal in dried form, take the leaves out of the box and put them in a laboratory blender to pulverize them.” The finished algae powder is then doused with liquid nitrogen, which has a temperature of minus 196 degrees Celsius. The extreme cold breaks open the cell walls and the valuable ingredients of the algae cells are released. The cell walls are particularly resilient because the algae use them to protect themselves from the extreme environmental conditions in the sea. “We then crush the result with a mortar, as you would with spices, and voilà, the algae extract is ready for the next processing step,” explains the biotechnologist.
Success with enzymes
The researchers then tested three different methods of extracting the ingredients in the laboratory to find out which one was best suited for each selected type of algae. They used mechanical, hydrothermal and enzymatic methods: “For mechanical extraction, we add the algae extract to a water-filled glass container that contains an ultrasonic homogenizer – you can think of it as a bit like a blender. When in operation, it generates high-frequency vibrations. The resulting ultrasound releases the ingredients from the extract. “In the hydrothermal method, we place the extract in a laboratory microwave. The electromagnetic waves generate heat and are intended to release the ingredients,” says the algae expert.
Depending on the goal, the methods used were more or less effective for the different algae. In the enzymatic method, protease enzymes break down proteins into their smaller components. These are peptides, which in turn consist of amino acids. The individual peptides and amino acids are suitable for use in food supplements, for fortifying existing foods, or for the conception of entirely new plant-based products for the food and feed market.
“We see particular potential for a follow-up project in the enzymatic extraction of algal proteins, i.e. peptides and amino acids from the red alga Porphyra dioica. These could be processed in a variety of ways in the food and feed market – particularly as a high-quality protein source equivalent to animal protein,” says Ana Romero. The scientist has great faith in the potential of the aquatic plant, which is usually given little attention by beach-goers and sunbathers. She is passionate about algae research and can imagine many more projects: “There are inconceivably large quantities that we can utilize – when I walk on the beach, I see all the untapped potential that the oceans provide us with every day – we just have to use it effectively,” the researcher says confidently.
