Introduction
Today, Atlantic salmon is Norway’s number two export in value, and the country wants to increase salmon production from 2 million tons today to 5 million tons by 2050. However, the industry faces multiple challenges, including a shortage of feed resources and high fish mortality due to exposure to multi-stressor conditions, such as sub-optimal nutrition, pathogens, environment, and handling stress, that need to be solved. To support further growth, we need to develop alternative feed ingredients from local underutilized natural resources that not only support high growth performance but also health and robustness of fish and that have low environmental impact. Microbial ingredients (MI) such as yeast and fungal proteins hold promise as alternatives; microbes have rapid growth rates, do not require agricultural land, use little fresh water, and can efficiently convert underutilized resources that do not compete with human food into high-quality proteins [1] . Thus, MI can meet the high protein demand of fish and they contain bioactive components with beneficial health effects. Foods of Norway , a Centre for Research-based Innovation at NMBU (foodsofnorway.net ) and related projects, including NordicFeed , ForestFeed and Resilient Salmon are developing novel MI from local resources from forest by-products, animal by-products and food waste by biorefinery processing. Functions and applicability of these MI are evaluated during critical life stages of fish, such as during seawater transfer.
Results
Our results have shown that C. jadinii yeast produced from Norway spruce tree sugars contains about 50-58% crude protein and has a favorable amino acid composition. In general, diets based on C. jadinii supported high growth performance and improved health and robustness of Atlantic salmon [1-2] . We have also shown promising results on growth performance, health and product quality of C. jadinii-based diets under field conditions during the grow-out phase in seawater. In the Resilient Salmon project we have evaluated the use of hydrolysed Debaryomyces hansenii- based products (LAN4 and LAN6) in functional feeds during multi-stressor conditions to develop nutritional programming and to improve health and robustness of Atlantic salmon. Results showed that after exposure to an acute hypoxia, fish fed LAN4 were able to prevent the secretion of plasma cortisol and IL-10, which are both biomarkers associated with immunosuppression. In the gills, differential gene expression of metabolic pathways associated with stress tolerance and oxidative regulation were found . In the intestine, goblet cells maintained higher levels of mucin proteins, involved in the protection of the intestinal tract [3] . Interestingly, after the M. viscosa outbreak in seawater, plasma specific IgM levels against the bacteria increased in fish fed LAN6, in addition to an upregulation of genes related to humoral immune response and complement activation in liver.
Foods of Norway has developed a life-cycle analysis model on C. jadinii from Norway spruce tree sugars, which shows that this yeast has a low environmental footprint. However, a techno-economic analysis of yeast production shows that the price of the sugars has the largest impact on cost due to greater demand for biofuel. Considering this , we are developing a fungal protein Paecilomyces variotii (PEKILO®) that can be produced from a range of cheaper input factors to reduce cost. The fungal protein has a higher crude protein content of 60-70%. Our recent results suggest that P. variotii supports high growth performance and has immunomodulating properties.
Conclusion
To help solve the raw material crisis, we need to further develop biotechnology processing that enables the use of a broader range of cheaper input factors from various waste streams and gasses to produce MI. This will facilitate upscaling and reduce costs to meet requirements of the aquaculture industry.
References : [1 ] Agboola, J.O., et al., 2021. Doi: 10.1038/s41598-021-83764-2. [2 ] Morales-Lange el al ., 2021. Doi: 10.3389/fimmu.2021.708747. [3 ] Morales-Lange el al ., 2022. Doi: 10.3389/fimmu.2021.708747.