In 1811, prof.Henri Braconnot, Director of the biological garden at Nancy, France isolated a fibrous substance from certain type of mushroom. He further observed that this substance did not dissolve in aqueous acidic solution, e.g. sulfuric acid. A decade later, the same substance was found to be present in certain insects as well and in 1823 Ojear (sometimes Odier) named it ‘Chitin’ (from greek khiton meaning envelope) .In 1859, prof. C.Rouget subjected chitin to alkali treatment and observed that unlike chitin, the substance resulting after alkali treatment dissolved in acids; however, it was not until 1894 that this substance was named ‘Chitosan’ by Hoppe-Seyler. In thr mean time, in 1878, Ledderhose proposed chitin to be made of glucosamine and acetic acid.
Chitin and chitosan are described as a family of polyglucosamine consisting of various amounts of (1, 4) linked residues of N-acetyl-2-amino-2-deoxy-D-glucose and 2-amino-2-deoxy-D-glucose residues. Chitin sample have a low amount of deacetylated units and hence it is insoluble in acidic aqueous media (fig. 3). On the other hand, the amount of deacetylated units in chitosan samples is high enough to allow the amino sugar to dissolve in acidic aqueous media. Chitin is the second most abundant natural occurring compound in nature after cellulose and it is found in the structure of a wide number of invertebrates (crustaceans’ exoskeleton, insects’ cuticles) and the cell walls of fungi, among others. On the other hand, chitosan only occurs naturally in some fungi (Mucoraceae). (Austin et al., 1981, Muzzarelli et al., 1986).
When lactic acid is produced using the fungal strain Rhizopus oryzae, a considerable amount of fungal biomass whose cellular wall is primarily composed of chitin was concurrently produced (Yusof and Lim 2001). Chitin is considered to be the secon most abundant biopolymer in the biosphere. Chitin is a natural... [continues]
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