ABSTRACT
The production of chitin in biomass has been evaluated to be as abundant as that of cellulose, with a yearly production within 1010-1012 T (4,5). This polymer is present in most of the families of living species (5). Thus, it constitutes the structure polymer of the cuticles of all the arthropods and the endoskeletons of all the cephalopods. It is also very often present at the cell wall and in the extracellular matrix of most fungi. It is encountered in numerous microorganisms, in some algae, etc. Chitosan is much less present in living media and to date it has only been observed in some microorganisms, particularly of fungal nature (6). This lack of occurrence explains why the latter polymer, whose direct applications are much more important than that of the former, is essentially produced from chitin. It is noteworthy that both chitin and chitosan in their polymeric form are completely absent in numerous animals including mammals. Nevertheless, the N-acetylglucosamine unit is largely widespread in the chemical structure of the other GAGs and the glycoconjugates such as glycoproteins and glycolipids (7). On the other hand,
Figure 9.1 Chemical structure of chitin and chitosan.
