Chitin, a β-(1→4)-linked polymer of 2-acetamido-2-deoxy-d-glucose (N-acetyl-d-glucosamine), exists in the exoskeletons of insects, crustaceans and the cell walls of fungi and algae. Its N-deacetylated derivative, chitosan, can be obtained using concentrated alkali and high temperature. Recently, chitosan is receiving more and more attention since it can be widely used in many areas such as biomedical engineering, fiber industry, environmental protection, functional food and cosmetics.