Seaweed is more than the wrap that keeps rice together in sushi. Seaweed biomass is already used for a wide range of other products in food, including stabilising agents. Biorefineries with seaweed as feedstock are attracting worldwide interest and include low-volume, high value-added products and vice versa. Scientific research on bioactive compounds in seaweed usually takes place on just a few species and compounds. This paper reviews worldwide research on bioactive compounds, mainly of nine genera or species of seaweed, which are also available in European temperate Atlantic waters, i.e. Laminaria sp., Fucus sp., Ascophyllum nodosum, Chondrus crispus, Porphyra sp., Ulva sp., Sargassum sp., Gracilaria sp. and Palmaria palmata. In addition, Undaria pinnatifida is included in this review as this is globally one of the most commonly produced, investigated and available species. Fewer examples of other species abundant worldwide have also been included. This review will supply fundamental information for biorefineries in Atlantic Europe using seaweed as feedstock. Preliminary selection of one or several candidate seaweed species will be possible based on the summary tables and previous research described in this review. This applies either to the choice of high value-added bioactive products to be exploited in an available species or to the choice of seaweed species when a bioactive compound is desired. Data are presented in tables with species, effect and test organism (if present) with examples of uses to enhance comparisons. In addition, scientific experiments performed on seaweed used as animal feed are presented, and EU, US and Japanese legislation on functional foods is reviewed.

Bioactive compounds in seaweed: functional food applications and legislation

Sulfated fucans, frequently referred to simply as fucans, constitute a class of polysaccharides first isolated in 1913. For many years fucans were regarded only as a potential source of l-fucose, although their anticoagulant activity was known. Even as the potent effects of fucans on physiological systems have become better characterized, structural studies have lagged behind. Recently the search for new drugs has raised increased interest in sulfated fucans. In the past few years, several structures of algal and invertebrate fucans have been solved, and many aspects of their biological activity have been elucidated. From this work emerges a more interesting picture of this class of polysaccharides than was previously suspected. The availability of purified fucans and fucan fractions with simple, but varied structures, in conjunction with the development of new enzymatic tools, demonstrate that the biological properties of sulfated fucans are not only a simple function of their charge density but also are determined by detailed structural features.

Sulfated fucans, fresh perspectives : structures, functions, and biological properties of sulfated fucans and an overview of enzymes active toward this class of polysaccharide

The seasonal chemical profiling of kelp species has historically either being carried out on only a single species or the data dates back over 60 years. This research highlights a detailed chemical composition profile of the four kelp species Laminaria digitata, Laminaria hyperborea, Saccharina latissima and Alaria esculenta over a 14-month period. These kelp species were selected due to their identified potential for cultivation. They were chemically characterised to identify seasonal variations and predict best harvest times. Components of interest included the carbohydrates cellulose, laminarin, alginate and mannitol as well as proteins, ash, metals, moisture, polyphenolics, total carbon and nitrogen content. The highest yields of lamianrin and mannitol coincided with the lowest yields in ash, protein, moisture and polyphenols. The implications of these observations for use of kelp species as a fermentation substrate are discussed.

The seasonal variation in the chemical composition of the kelp species Laminaria digitata, Laminaria hyperborea, Saccharina latissima and Alaria esculenta

Brown seaweed fucoidan: biological activity and apoptosis, growth signaling mechanism in cancer.

Marine algae contain large amounts of polysaccharides, notably cell wall structural, but also mycopolysaccharides and storage polysaccharides (Kumar et al. 2008b; Murata and Nakazoe 2001). Polysaccharides are polymers of simple sugars (monosaccharides) linked together by glycosidic bonds, and they have numerous commercial applications in products such as stabilisers, thickeners, emulsifiers, food, feed, beverages etc. (McHugh 1987; Tseng 2001; Bixler and Porse, 2010). The total polysaccharide concentrations in the seaweed species of interest range from 4-76 % of the dry weight (Table 1). The highest contents are found in species such as Ascophyllum, Porphyra and Palmaria, however, green seaweed species such as Ulva also have a high content, up to 65 % of dry weight.

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Algal Polysaccharides, Novel Applications and Outlook

A new spectrophotometric procedure was developed for the quantitative determination of fucoidan and alginic acid and used for their analysis in extracts from biomass of 17 species of brown algae collected from coastal waters of the Kamchatka peninsula. In addition, neutral monosaccharides and mannitol were determined in the hydrolysis products of the alga biomass samples. The polysaccharide composition was shown to substantially depend on the algal species. The alginic acid content was maximal in the Alaria marginatablades; all the other representatives of the order Laminariales also are useful sources of this polysaccharide. At the same time, the fucoidan content is rather low in Laminariales. The highest content of fucoidan was found in Saundersella simplex, but Chordaria flagelliformisand Fucus evanescensare more practical fucoidan sources; the available supplies and the sugar composition make the latter alga the most suitable for the complex processing to prepare mannitol, fucoidan, and alginic acid.

Polysaccharides of Algae: 55. Polysaccharide Composition of Several Brown Algae from Kamchatka

Quantitative determination of mannitol, fucoidan and alginate in different parts of the thallus (the blade, the midrip, the sporophylls, and the stipe with rhizoids) of the brown alga Alaria fistulosa, collected from the coastal waters of Paramushir Island, was carried out. Sporophylls were shown to differ considerably in carbohydrate composition from all other parts of the plant. In particular, the fucoidan content in sporophylls is several times as high as that in the blade. Alginate preparations isolated from sporophylls and from blade have different proportions of monomers (mannuronic acid and guluronic acid residues) and different molecular masses. Fucoidan preparations isolated from these parts of the plant differ slightly in the sulfate content. Their specific feature is a rather high galactose content comparable with the content of fucose. The sporophylls of A. fistulosa may be regarded as a rich source for practical isolation of fucoidan.

N. G. Klochkova

Papers

Polysaccharides of Algae: 55. Polysaccharide Composition of Several Brown Algae from Kamchatka

Polysaccharides of Algae 58. The polysaccharide composition of the Pacific brown alga Alaria fistulosa P. et R. (Alariaceae, Laminariales)