PhysOrg reports that commercially produced microalgae could become a sustainable fish feed ingredient, a project from the National Food Institute, Technical University of Denmark, has shown. In the project, concepts have been developed to grow, harvest, dry and store two types of algae that are rich in protein, antioxidants and omega-3 fatty acids.

Traditionally fishmeal — which is an important ingredient in fish feed — has been made from industrial fish such as sprat and sand eel that are unfit for human consumption. As a result of the increasing production of fish feed for the growing aquaculture industry it is becoming both environmentally and economically unsustainable to continue this practice.

The hunt for sustainable fishmeal alternatives has, among other things, focused on microalgae because they contain almost all the nutrients fish need. However, commercial production of microalgae through photosynthesis has until now proved to be too expensive, so new methods are needed in order for microalgae to become a cost-effective fish feed ingredient.

In the project at the National Food Institute, researchers have extensively screened different microalgae species and have identified two types that have a high content of protein and/or omega-3 fatty acids, as well as antioxidants, which are suitable for growing under Danish conditions. They have also developed methods to harvest, dry and store the algae biomass, which ensure that valuable substances in the biomass deteriorate as little as possible.

Chlorella pyrenoidosa Image: www.healthbenefitsofeating.com

The two species (Nannochloropsis salina and Chlorella pyrenoidosa) are grown in industrial process water – a low-price growth medium rich in nutrients while being free from toxic compounds.

The new drying process is environmentally friendly. It uses 30% less energy than the spray drying techniques that are currently in use. In the new process, the microalgae are dried in a stream of air in a specially designed drying chamber. The drying process is far gentler on pigments and omega-3 fatty acids in the biomass than spray drying.

Researchers expect to be able to modify the new drying process so it can be used on other algae species and other types of biomass. The National Food Institute has a patent pending for the technology.

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