Hydroxyl groups are ubiquitous in polysaccharides structure and involved in most of the chemical modifications. The most useful functionalities are ester, ether, amide, amine and alkyl groups. The starting materials could be a natural or depolymerized polymers and the reaction considered with a regioselective point of view.
In this review, we will focus on chitin polysaccharide, which is extracted according to industrial processing from exoskeleton of several marine crustaceans. A subsequent deacylation provides chitosan. This marine polysaccharide is very similar to cellulose, a widespread fiber plant organic polymer, except for an amine group on the C2 position instead of a hydroxyl group. Furthermore, seaweeds provide the most abundant sources of polysaccharides: alginates, agar/agarose, carrageenans and fucoidans. In order to improve the original physicochemical and biochemical properties, we will highlight the chemical modifications involving the listed marine polysaccharides of interest.