New research from the DTU National Food Institute and Aarhus University shows that microorganisms can be used to specifically alter the amino acid composition of plant-based foods, making them more nutritious and therefore healthier.
In practice, this means that researchers can extract greater nutritional value from the same quantity of plant-based foods or animal feed.
"Plant proteins do not contain the right amino acids in sufficient quantities to be an ideal source of nutrition for humans. Our solution is to use microorganisms to enrich plant-based foods with essential amino acids and important vitamins," says Associate Professor Christian Solem from the DTU National Food Institute.
Proteins are made up of amino acids. Humans need essential amino acids, which the body cannot produce itself. A protein is called 'complete' when it contains all nine essential amino acids in sufficient quantities.
Many plant proteins are relatively low in one or more essential amino acids.
Fermentation using specific microorganisms is the solution
The researchers have been working with a wide range of plant proteins which, through fermentation, can be effectively enriched with the essential amino acid lysine.
"The interesting thing is that we can use microorganisms to improve the amino acid profile of plant-based ingredients while also making plant proteins easier to digest by partially breaking them down. This is particularly beneficial because many crops contain antinutrients that make it harder for our bodies to absorb the nutrients found in plant-based foods, says Christian Solem, adding:
"We have demonstrated the principle using the essential amino acid lysine and will soon have solutions ready that will also allow us to enrich crops with two other essential amino acids."
The results form part of the NextOrganic project, which focuses on animal feed, but the technology developed can also be used to improve plant-based foods for human consumption.
The researchers believe that this method could help to alleviate malnutrition in low-income countries, which may be caused, for example, by a diet that is too heavily based on plants.
The researchers have mainly worked with faba beans and rapeseed press cake, which are produced in large quantities in Denmark and the rest of Northern Europe, but the technology has also been shown to work well with other plant crops.
Faba beans are a protein-rich crop used for both animal feed and human food. Rapeseed press cake is the protein-rich material left over once the oil has been pressed from rapeseed. Both can serve as alternatives to, for example, imported soya in animal feed.
Better animal feed
In animal feed, a deficiency of essential amino acids can mean that animals grow more slowly and become ill. In practice, the problem is solved either by feeding the animals more protein than they actually need, or by adding essential amino acids produced through fermentation.
"In organic pig and poultry production, it is not permitted to add synthetic amino acids to the feed, so overfeeding with protein is the only option. If the animals are given more protein than they can utilise, they excrete more nitrogen via urine and faeces, which places a strain on the environment," says Jan Værum Nørgaard, professor at the Department of Animal and Veterinary Sciences at Aarhus University.
If the composition of the protein can be improved, this can therefore both make the feed more efficient and reduce waste and nitrogen pollution.
How the researchers did it
The researchers employed a two-stage fermentation process.
First, they treated faba beans and rapeseed press cake with the bacterium Bacillus subtilis subsp. natto. This breaks down plant proteins into smaller components and releases various sources of nitrogen.
The researchers then added another microorganism, Corynebacterium glutamicum, which uses these nitrogen sources to produce lysine.
Lysine is one of the nine essential amino acids that humans must obtain through their diet.
Following fermentation, the lysine content had increased 3.4-fold in faba beans and 3.6-fold in rapeseed meal. The researchers measured 37.5 and 29 grams of lysine per kilogram of dry matter, respectively.
The researchers are currently working on solutions for two other essential amino acids.
Facts about the study
The study, originally titled 'A Novel and Simple Fermentation Approach for Adjusting the Amino Acid Composition in Plant Biomasses to Enhance Nutritional Value for Humans and Animals' has been published in the scientific journal "Journal of Agricultural and Food Chemistry".
The study was carried out in collaboration between the DTU National Food Institute and Aarhus University and forms part of the NextOrganic project, which has received funding from ICROFS under the Green Development and Demonstration Programme (GUDP).
