1. Macroalgal polysaccharides and their bioactive derivatives

1.1 Description of the various algal polysaccharides

Depending on the nature of their pigments, macroalgae are classified into three main divisions: green algae or Chlorophyceae, red algae or Rhodophyceae and brown algae or Phaeophyceae. Marine macroalgae synthesize a wide range of polysaccharides, which are essentially constituents of their cell walls (parietal polysaccharides) and differ according to their lineage. These wall constituents have functional properties for thickening or gelling aqueous systems. These thickening properties are the basis of their use in the phycocolloid industry, due to their very low cost of access (annual tonnage of 33,000 t for carrageenans and 30,000 t for alginates)