Environmental impacts of the filamentous fungi Paecilomyces variotii (PEKILO®) as a novel protein source in feeds for Atlantic salmon (Salmo salar)

The present study investigated environmental impacts associated with greenhouse gas (GHG) emission, economic Fish in Fish out ratio (eFIFO), waste outputs, and food-feed competition of feeding diets containing the filamentous fungus Paecilomyces variotii (PEKILO®) to Atlantic salmon (Salmo salar) pre-smolts. To achieve this, a feeding trial was conducted using four experimental diets. The control diet was based on fishmeal, soy protein concentrate, and wheat gluten meal. Diets 1, 2, and 3 were formulated so that P. variotii replaced 5, 10, and 20 % of the crude protein (CP) content of the control diet originating mainly from fishmeal, soy protein concentrate, and wheat gluten meal. Dietary inclusion of P. variotii affected simulated environmental indices such as GHG emission (P < 0.001); this index was P. variotii-dose-dependent, as illustrated by negative linear models (P < 0.001, adjusted R-squared = 0.96). Dietary inclusion of P. variotii was negatively correlated with eFIFO (P < 0.001, adjusted R-squared = 0.82). Dietary inclusion of P. variotii reduced food-competition feedstuff (FCF) in the diets (P < 0.001), as well as the amount of FCF to produce one kg of Atlantic salmon (P < 0.001). Relative to the control diet, solid nitrogen waste output, expressed as g kg⁻¹ fish produced, was increased (P < 0.0001) in fish fed Diet 3. Conversely, linear decreases in solid phosphorous, magnesium and potassium (P < 0.0001) wastes expressed as g kg⁻¹ fish produced were associated with increasing dietary inclusion of P. variotii. Likewise, linear decreases in dissolved nitrogen, magnesium, and potassium (P < 0.0001) wastes were observed with increasing replacement of the CP content of the control diet with P. variotii. Based on this assessment, P. variotii is a relevant alternative protein source with a low environmental footprint for use in Atlantic salmon feeds. Future novel feeds for Atlantic salmon should expand the use of alternative protein- and lipid-rich materials with a low ecological footprint that are produced according to a circular bioeconomy principle and utilize non-food-competing feedstuff (NFCF) such as P. variotii to move the industry towards sustainability.