*4.1.3 Chitosan*

After cellulose, chitosan is the world's second most abundant polysaccharide. Because this biopolymer is primarily derived from waste products in the shellfish industry, commercial supplies are currently plentiful, and as a result, it is reasonably priced. Chitosan is a biocompatible, biodegradable, and nontoxic material that is ideal for packaging films. Chitosan is more versatile than chitin due to its structural properties and the ability to create films with different properties and barriers [55]. This biopolymer has been demonstrated to have excellent film and coating properties, as well as an inherent antimicrobial property. As a result, many chitosan-based films have been fabricated and applied in the food packaging industry. However, its high-water sensitivity causes a loss of barrier properties, limiting its industrial application for packaging. Blending this polysaccharide with other more water-resistant polymers has proven to be a viable solution to the solubility problem. Furthermore, it has been demonstrated that reinforcing this biopolymer with fillers can result in novel composites with improved physical properties, such as water resistance, without sacrificing biodegradability.
