The Potential for ‘Next-Generation’, Microalgae-Based Feed Ingredients for Salmonid Aquaculture in Context of the Blue Revolution

Abstract

Microalgae-based ingredients have potential to ensure continued growth of salmonid a q u a c u l t u r ef o rg l o b a ls u s t a i n a b l ef o o ds e c u r i t yi nt h eb l u ee c o n o m y .A l g a lb i o r e f ineries must valorize the entire crop to grow profitable microalgae-based economies. With massive growth and demand for novel sustainable ingredients, farmed salmonid feed sectors are highly promising areas to focus on. Microalgae-based ingredients for salmonid feeds may have market advantages in terms of lower input costs, aerial footprint, wastewater remediation benefits and carbon credits for industrial CO 2 conversion. A handful of microalgae-based ingredients have been proposed as candidates to supply well-balanced nutrients and immunostimulatory compounds. However, technical gaps exist and need addressing before the industry could economically incorporate microalgae-based ingredients into commercial feeds. Current knowledge on comprehensive biochemical composition is incomplete, highly heterogeneous, and information on their nutritional value is scattered and/or inconsistent. The aim of this chapter is to consolidate relatively fragmented data on biochemical composition and nutritional value of microalgae-based ingredients focusing on farmed salmonid feeds. Presented are discussions on the potential for such 'next-generation' ingredients, opportunities/challenges for their use and a compendium of studies evaluating their performance in feeds for economically relevant farmed salmonids, including rainbow trout (Oncorhynchus mykiss), Arctic charr (Salvelinus alpinus) and Atlantic salmon (Salmo salar).

Projected declines in global DHA availability for human consumption as a result of global warming

“…Microalgae production is becoming popular as a source of DHA. There are several products now on the market that are rapidly being added as nutritional supplements and aquaculture feeds (Sprague et al 2017;Tibbetts 2018). Phototrophic production of microalgae (i.e., using light) results in slower production but yields a combination of EPA and DHA, while heterotrophic production has high yield, but only produces DHA.…”

“…The problem is that, in recent years, ruminants are more often fed grain-based diets (and which contain lower amounts of n-3 FA), due to increased forage prices and land use competition (Provenza et al 2019), which then lowers the DHA supply in meat for consumers. There have also been efforts to produce DHA by other means, such as microbial and microalgae production (Sprague et al 2017;Tibbetts 2018) and transgenic crops (Napier et al 2019), although there is uncertainty around the future development and availability of these sources. However, overall, DHA is currently most effectively obtained by eating fish and seafood, and/or taking fish and/ or algal oil supplements (Arts et al 2001;Calder 2015).…”

Microalgal Aquafeeds As Part of a Circular Bioeconomy

“…Technically, aquafeeds within the above compositional ranges can be produced entirely from microalgae; however, other factors affecting the FCR to be considered include feed attractiveness (e.g., smell, taste), accessibility (e.g., cell/pellet size, buoyancy), and nutrient availability [34]. The high cell-wall recalcitrance of most microalgae is detrimental to digestibility and assimilation of intracellular nutrients, especially for carnivorous fish with a short digestion phase (e.g., salmon) [35]. Disruption of the cell wall of Chlorella vulgaris and Nannochloropsis gaditana has been reported to improve nutrient digestibility (especially for essential amino acids, carbohydrates, and starch) in Atlantic salmon (Salmo salar L.) [36] and protein and fat digestibility in Nile tilapia (Oreochromis niloticus) [37] but may cause the release of antinutritional compounds [38].…”

“…Given that algae are expensive to produce, their use as bulk ingredients for formulated feed production is likely to require improved production efficiency and further cost reduction through the use of biorefinery approaches [17]. However, the wide range of pigments, fatty acids, vitamins, minerals, and bioactives of microalgae make them excellent high-value nutrient additives and supplements to blend into a wide range of aquafeeds [35]. For instance, a 0.5-2.5% Spirulina sp.…”

Ameliorating process parameters for zeaxanthin yield in Arthrobacter gandavensis MTCC 25325

“…Zeaxanthin is a xanthophyll commonly found in corn, egg yolk, oranges, yellow fruits, flowers and vegetables. It imparts a yellow colour to skin and egg yolk of birds and skin colouration to swine and fish (Tibbetts 2018;Zaheer 2017) and is a well-known prophylactic agent that has been reported to exert preventive action against age-related macular degeneration and cancer (Hirahatake et al 2019). Other application includes its use as food/ feed additive and colourant (E161h) in cosmetics and food industries approved by the European Union (EU).…”