1. Introduction
Chitosan (CS), the fully or partially deacetylated derivative of chitin, is one of the abundant, renewable, biocompatible,biodegradable, and nontoxic carbohydrate polymers [1,2]. There-fore, CS has a variety of current and potential applications in pharmaceutics [3], biotechnology [4], and food science [5]. How-ever, due to the very strong intramolecular and intermolecular hydrogen bonds between hydroxyl groups and amino groups [6],CS has a major shortcoming of poor solubility. It is only soluble in acidic solution with pH