Chitin the precursor of chitosan, is a linear polymerof mainly -(1 → 4)-2-acetamido-2-deoxy-d-glucopyranose unitsand low amounts of -(1 → 4)-2-amino-2-deoxy-d-glucopyranoseresidues. The polymer is highly acetylated and is insoluble in water.It is one of the most abundant biological materials in the world andis after cellulose and next to lignin the most biosynthesized poly-mer. When the degree of N-acetylation (DA) is lower than 50% it isentitled chitosan