Microbial raw materials as source for protein and EPA and DHA for use in aquafeed

Cultured microorganisms represent a sustainable feed resource that can satisfy the aquaculture industry's need for feed stocks with high content of EPA and DHA. In this project, marine microorganisms such as thraustocytides and photosynthetic microalgae have been produced with high levels of DHA and EPA. These two groups of organisms have different challenges for being sustainable sources of fish feed, and these challenges have been addressed in the project. For thraustocytes, the production technology is well established, but it needs improvements to increase the productivity of DHA by 50-100%, which have been the target of the project. For microalgae, productivity must be at least ten times higher than it is today, and there is also a need to optimize the culture conditions to increase lipid and EPA / DHA levels. Several attempts in this project have been made to address these challenges. The results show that the lipid and DHA productivity and lipid and fatty acid composition of thraustocytides are affected by the culture conditions (nutrient source). Also, the productivity of EPA and DHA in phototropic microalgae can be optimized by selecting strains and optimizing nutritional limitation. So far, most focus has been placed on the effect of nitrogen limitation on lipid productivity. The microbial biomass is used in feeding experiments of fish. Feeding trials were carried out on salmonids and European sea bass. the results showed that digestibility of the microorganisms varied somewhat and can be improved by pre-treatment such as breaking the cell wall. Several of the microorganisms studied had rigid cell walls, and breaking down the cell wall would have improved digestibility. The main result of the project show that thraustocytides and photosynthetic microalgae represent a possible source of lipid and protein for a future feed source.

Environmental impact of aquaculture: The project has positive effect on the environmental effects of aquaculture. New sustainable aquafeed resources is important for future increase in the aquaculture production. New resources for omega 3 fatty acids is important for avoiding over-fishing of marine fish stocks. Increase efficiency aquaculture production: Producing aquafeed from low trophic layers will increase the energetic efficiency of the aquaculture production. Develop frendly products from aquaculture: Aquafeed based on microbial raw material can be regarded as a friendly product of aquaculture. This has low environmental impacts, and aquafeed with high content of microalgae/microbial biomass can be marketed as friendly food. Open new markets: Green labelled fish products that are fed on microalge and microbial based feed can open new market possibilities in deifferent countries. Aquafeed from lower tropic layers can be an important selling argumet for new markets.

The aquaculture industry contributes with half of the global seafood consumption and this share is expected to increase (FAO, 2013). Limited availability of marine raw materials has created a need for new sustainable feed resources to cover the need for proteins and EPA/DHA to ensure the future growth. In this project we will explore the potential of cultured marine microorganisms to become a new sustainable feed source for aquaculture. Marine microorganisms are the natural source of essential fatty acids in the marine food web, and in additionthey provide proteins, carbohydrates, vitamins, minerals, pigments and antioxidants.We will focus on two groups: 1) the heterotrophic thraustochytrids, which accumulate high levels of DHA-rich lipids, and 2) phototrophic microalgae, rich in EPA and/or DHA. Both groups can be cultured based on sustainable carbon and energy sources (light/CO2 and organic waste) and have high protein contents. We will use biotechnological approaches to improve the production yield of omega-3 fatty acids in of both groups. The EPA/DHA-contents and the productivities will be increased byoptimization of the cultivation conditions to utilize the maximum physiological potential of the strains, and by applying selection pressures to enrich for improved strains. The last strategy can also be combinedwith a random mutagenesis. The microbial biomass will be evaluated in feeding experiments with salmonids, European seabass and tilapia, by analysing digestion, growth and functionality. The partners in the project are from Norway (NTNU, SINTEF Fisheries and Aquaculture, SINTEF Materials and Chemistry), Germany (ILU), Turkey (University of Ege and MEDFRI) and Iceland (MATIS).