ABSTRACT
Chitosan is a functional and basic linear polysaccharide prepared by N-deacetylation of chitin in the presence of alkaline. In general, deacetylation cannot be completely achieved even under harsh treatments. The degree of deacetylation usually ranges from 70% to 95%, depending on the method used. Thus, chitosan is available with various molecular weights and deacetylation degrees. Chitosan is insoluble in water, alkali, and organic solvents, but is soluble in most solutions of organic acids when the pH of the solution is below 6. The industrial production and application elds of chitosan have been steadily increasing since 1970s. Early applications of chitosan have been centered on the treatment of wastewater, heavy metal adsorption, food processing, immobilization of cells and enzymes, resin for chromatography, functional membrane in biotechnology, animal feed, and so on. The recent trend is toward producing high-valuable industrial products such as cosmetics, drug carriers, and pharmaceuticals. Chitin and chitosan are known to exhibit antitumor, antibacterial, hypocholesterolemic, and antihypertensive activity (Kim and Rajapakse 2005). The main motive for the development of new applications for chitosan lies in the fact that it is a very abundant polysaccharide, as well as nontoxic and biodegradable. Despite its functions and importance as a biomaterial, the applications of chitosan in food and biomedical industries are narrowed owing to its poor solubility, high molecular weight, and viscosity. There is evidence about the nonabsorption or indigent absorption of chitin and chitosan in the human intestine due to lack of enzymes to cleave the β-glucosidic linkage in chitosan. Since chitosan is a large water-insoluble biopolymer, it is dif- cult for the mammalian body to absorb it. In this respect, enzymatic hydrolysis of chitosan to obtain oligomers is of great interest recently (Jeon and Kim 2000).
