Principles of Biochemistry (2+1)

3.3.4.4 Alginic Acids

Alginic acid is a linear copolymer with homopolymeric blocks of (1-4)-linked ß-D-mannuronate (M) and its C-5 epimer α-L-guluronate (G) residues, respectively, covalently linked together in different sequences or blocks.   It is (algine, alginate) is a viscous gum that is abundant in the cell walls of brown algae.  Brown Seaweeds are used for extraction of alginic acid. Commercial varieties of alginate are extracted from brown seaweed, including the giant kelp Macrocystis pyrifera, Ascophyllum nodosum and various types of Laminaria, Sargassum sp, Turbinaria ornata, Padina sp etc.

Uses: Alginic acid is used in the food industry, for thickening soups and drinks, ice cream, tinned meats and jellies. Alginate absorbs water quickly, which makes it useful as an additive in dehydrated products such as slimming aids, and in the manufacture of paper and textiles is used commercially for toothpastes, soaps, fabric printing, and a host of other applications. It forms a stable viscous gel in water, and its primary function in the above applications is as a binder, stabilizer, emulsifier, or moulding agent.  It is also used for waterproofing and fireproofing fabrics, as a gelling agent, and cosmetics, and as a detoxifier that can absorb poisonous metals from the blood. Alginate is also produced by certain bacteria, notably Azotobacter species.