Alginate Extraction

Alginates exist in seawater as insoluble mixed salts such as calcium, sodium, and magnesium salts. The properties of alginate vary from species to species, so choosing which algae to harvest depends on the availability of a particular species and the properties of the alginate they contain. Alginate is a vital polysaccharide widely used in the food, textile, printing, and pharmaceutical industries for its viscosity-increasing and gelling properties. The primary commercial sources of alginate are Ascophyllum, Durvillaea, Ecklonia, Laminaria, Lessonia, Macrocystis, Sargassum, and Turbinaria. The most important of these are kelp, Macrocystis, and Ascophyllum nodosum. Alginate biopolymers can represent up to 40% of brown seaweed dry matter. The amount and quality of alginate in brown seaweed depends on many factors, such as the algae, harvest season, tissue type, and age. The principle of extracting alginate from seaweed is to convert all alginate into sodium salt, dissolve it in water, and then filter to remove seaweed residue. The alginate must then be recovered from the aqueous solution.