It is often converted into chitosan by deacetylation which renders selleck catalog it soluble in acids. The word ��chitosan�� is used for both partially and completely N-deacetylated chitosans. Commercial chitin and chitosan are copolymers of 2-acetamido-2-deoxy-D-glucose (N-acetyl glucosamine, GlcNAc: A-unit) and 2-amino-2-deoxy-D-glucose (glucosamine, GlcNH2: D-unit) with ��-D-(1 �� 4) glycoside linkages. The chemical structures of chitin and chitosan are illustrated in Figure 1.Figure 1Chemical structure of chitin and chitosan.Chitosan with vast and diverse interesting (antifungal, antibacterial, scavenging, and antioxidant activities; elicitation of plant defense; cholesterol lowering effect; wound healing; and film and fiber forming) properties has potential for applications in many areas such as food, medicine, and agriculture [1�C5].

It has been employed for various applications in food industries as an antimicrobial agent; as a feed supplement, food additive, and food preservative; purification agent for water and extends shelf life of fresh fruits and vegetables [2, 4, 6�C15]. The various properties and biological activity of chitosan and its derivatives appear to be dependent on their molecular weight; molecular weight distribution; and DA [16�C19]. Low molecular weight chitosans have been used as food coating materials [4, 17, 19]. Intermediate molecular weights of chitosan (100 < Mw < 500kDa) and chitosan-based polysaccharides have been used in food industry due to their film forming ability [4, 14].

The biological and antimicrobial activities and effectiveness of chitosan or its derivatives have been found to be dependent on its degree of acetylation (DA) and molecular weight in various applications [16�C20]. The use of chitosan in many applications is in the form of solution at moderate concentration and using intermediate molecular weights [21]. Large macromolecules of chitosans are less effective or develop high solution viscosities, which can cause practical problems in their applications. Development of an efficient process for fragmentation and reduction in molecular size of chitosan without altering its DA is interestingand a desirable goal. Chitosan can be fragmented by acid or enzymatic hydrolysis. Acid hydrolysis has an advantage over enzymatic hydrolysis, because enzymes are expensive.

Acid hydrolysis is a convenient way to obtain a wide range of fragments of different molecular weights by changing the reaction time and/or acid concentration. Acid hydrolysis of chitosan has been studied by several researchers. In most of the reports, studies were focused on depolymerization of oligomers Dacomitinib and/or depolymerization of chitosan for preparation of small macromolecules such as chitooligosaccharides [22�C25] using high concentration of acids (CHCl > 1N). These studies resulted in oligomers, monomers, or macromolecules having larger polydispersities compared to the original ones.