Alginate Fibers

Abstract

Alginates are polysaccharides found as the cell wall constituents in brown algae (Phaeophyceae) which is considered a seaweed. Although some quantities of alginate are found in most species of brown algae, certain species (Laminaria, Lessonia, Macrocystis, Sargassum) contain 30–45 % alginate by dry weight, and these species are used for extraction. In China, about 2 million tons of seaweeds are artificially cultured for alginate production. In 2009, about 27,000 tons of alginate with an estimated value of $318 million were reportedly produced. Alginates are extracted from raw seaweeds by treating with sodium hydroxide when the alginates in salt form are converted into the water-soluble sodium alginate [08Qin]. Chemically, alginates are linear polymers composed of 1,4,-β-d-mannuronic acid (M) and α-l-guluronic acid (G) residues. The amount of M and G residues and the proportion of the blocks of M and G residues vary between different species and are responsible for the variations in properties between the different alginates [08Qin]. Table 28.1 lists the percentage of M and G residues and the block structures found in commercially available alginates extracted from different types of Brown seaweeds.