18th December

Seaweed - an untapped source of protein and bioactive compounds for aquaculture

Simon Faulkner, Ocean Harvest Technology

Seaweed is fast gaining a reputation as the ideal sustainable food source. Certainly, the nutritional properties of seaweeds are both unique and interesting, with some seaweeds having protein levels as high as 47%. Seaweed, therefore, represents an untapped source of protein and has great future potential.

As the global population continues to rise, the need for sustainable, alternative sources of protein also increases. In fact, it is estimated that the worldwide requirement for food will increase up to 50% by 2030, thus highlighting the absolute need for sustainable development.
Recently, Ocean Harvest Technology worked in collaboration with a number of research institutes to evaluate the use of different seaweeds as a sustainable protein source for aquaculture.

Seaweed found on Ireland's west coast

Seaweed found on Ireland's west coast

Why seaweed protein?
Protein is the most expensive constituent of fish feed whereby global expenditure exceeds €1bn per annum. Fishmeal is a high-protein animal feed used extensively in aquaculture but uses wild fish stocks to feed farmed fish and is an unsustainable feed resource.

 

The ability of fishmeal supply to meet future demand is a massive global concern - especially given that aquaculture production is growing at a rate of nearly 9% per annum.

As wild fish stocks decline, the aquaculture industry faces a massive challenge to identify cost-effective and environmentally-friendly alternatives to fishmeal on which it is so heavily reliant.

Seaweed protein has the potential to provide a solution to this problem as it is relatively underexploited, contains high amounts of protein and can be cultured in a sustainable, environmentally-friendly manner.

Essential nutrients
Proteins are an important source of energy, present in all cells and are an essential component of most biochemical processes. Proteins comprise one or more chains of various amino acids, organised in a specific manner that give the protein a specific structure. When ingested, proteins are broken down into amino acids or short chains of amino acids called peptides. These amino acids play key roles in important metabolic pathways associated with maintenance, growth, reproduction, and immunity.
Amino acids can be classified as either essential or non-essential. Essential amino acids cannot be produced by the animal and must be sourced solely from the diet. Most seaweed species contain all of the essential amino acids and are also rich in some non-essential amino acids such as aspartic and glutamic acid.

In general, the protein content of seaweed ranges from 3-47% and considerable differences exist in the protein content of brown, green and red seaweeds. In contrast to brown seaweeds, red seaweeds contain higher levels of protein which can be up to 47% (Porphyra sp.).

Brown seaweeds can have protein levels up to around 20% (Alaria esculenta) whereas the levels found in green seaweeds are as high as 29% (Ulva lactuca). Differences in season, species and environment can have a significant impact on the composition of amino acids and protein in seaweeds.

Bioactive proteins
Seaweed is a natural source of biologically active proteins, amino acids and peptides. Two groups of bioactive proteins – lectins and phycobiliproteins – are present in some seaweed. Lectins are a group of carbohydrate-binding proteins that display anti-bacterial, anti-cancer, anti-HIV and anti-inflammatory biological activity; lectins have been successfully isolated from a number of seaweeds including Eucheuma sp. and Codium fragile.

Another group of proteins – phycobiliproteins – exhibit antioxidant, anti-inflammatory, cholesterol-lowering and antiviral activities to name but a few and have been isolated from the red seaweed, Palmaria palmata.

A number of bioactive amino acids are also present in seaweed. One such example is taurine – a bioactive amino acid required for some biological functions. Other bioactive amino acids present in seaweeds include laminine, kainoids, and mycosporine-like amino acids. These amino acids have a wide range of biological properties including antioxidant, hypotensive, insecticidal, anthelmintic, and neuroexcitatory activity.

In addition to bioactive amino acids, some bioactive peptides have been isolated from seaweed. These include carnosine and glutathione both of which are antioxidant peptides that protect cells from damage caused by reactive oxygen species. Another bioactive peptide produced by seaweed is Kahalalide F which is a cyclic depsipeptide with anti-cancer activity and is also active in the treatment of AIDS.

Seaweed protein in aquafeed
The functional biological properties of seaweed protein make it an excellent candidate for a natural, sustainable alternative to fishmeal in aquaculture. The capacity for large- scale production of seaweeds in Ireland, together with high-purity seaweed protein extraction developed by Ocean Harvest Technology further enhances the future potential. The availability of such sustainable protein sources is a prerequisite for our ability to continually produce high-quality and safe products.

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