ABSTRACT
The high molecular weight of chitin and chitosan, which results in their poor solubility at neutral pH values, limits its potential uses in the elds of food, health, and agriculture. However, most of these limitations can be overcome by chitin and chitosan oligomer or monomer. In humans, chitin monomers are precursors of the disaccharide units in glycosaminoglycans (such as hyaluronic acid, chondroitin sulfate, and keratin sulfate), which are necessary to repair and maintain healthy cartilage and joint function. Chitosan oligomers in food and nutrition elds have the ability to improve food quality and human health progression. For large-scale production of chitin/ chitosan oligomers, acid hydrolysis is commonly used to cleave glycosidic linkages of chitin and chitosan. However, the resultant oligomers are generally not considered to serve as safe bioactive materials because of a possibility of contamination of toxic chemical compounds. As a result, the enzymatic hydrolysis of chitin and chitosan has been proposed as a preferred method for the production of bioactive chitin/chitosan oligomers during the past few decades. The hydrolytic enzymes include cellulase, protease, lipase, pepsin, chitinase, chitosanase, and lysozyme, although only chitinase, chitosanase, and lysozyme are believed to be specic. These chitinolytic and chitosanolytic enzymes produced by different kinds of organisms have different action mode and size specicity.
