**4. Chitosan parameters**

*Chitin and Chitosan - Physicochemical Properties and Industrial Applications*

is mechanical grinding of the raw chitin, and subsequent process of removing proteins, color compounds and inorganic salts takes place. The deproteinization process is usually performed with a dilute aqueous solution of sodium hydroxide at an elevated temperature [4, 5]. For protein removing also proteolytic enzymes were used [39, 40], but in the case of papain, trypsin and chymotrypsin, it was found that they did not completely remove the protein fraction. After deproteinization process, the residue is treated with dilute aqueous hydrochloric acid to dissolve the calcium carbonate. A similar effect can be obtained by using HCOOH, HNO3, H2SO4 or EDTA [5]. The decolorization process is based on extraction with ethanol, acetone or treatment with oxidizing reagents (KMnO4, NaOCl, H2O2). These activities allow to obtain chitin of required purity for its further transformation into chitosan. Chitosan from chitin obtained by chemical deacetylation is obtained at high temperature (above 100°C), under high pressure and in the presence of concentrated (40–50%) strong bases (usually NaOH). A typical industrial chitosan production process provides almost complete recovery of proteins, calcium oxide or calcium carbonate, carotenoid pigments and sodium acetate under the conditions of using sodium hydroxide as the deacetylating agent. However, this process has several disadvantages. It is not environmentally friendly as it consumes a large amount of energy and is also difficult to control leading to a heterogeneous product. The use of chitin deacetylase for the production of chitosan oligomers and polymers can potentially eliminate most of these drawbacks [41]. The advantages of enzymatic deacetylation are more pronounced in the processing of chitin oligomers, as these substrates are soluble in the aqueous medium and are therefore more susceptible to enzymes. The downside is the high cost of the enzyme and the requirement to use pre-processed chitin. The conditions of the chitin deacetylation process have a significant impact on the distribution of N-acetyl-D-glucosamine and D-glucosamine groups in the polysaccharide chain. Their location in the chain has a significant impact on the physicochemical properties of the material, such as crystallinity, solubility and susceptibility to degradation [3]. Depending on the final use, chitosan can be formed into a hydrogel, membranes, fibers, sponges and micro/

**142**

**Figure 9.**

*Chitosan formation from chitin by chitin deacetylation.*

nanoparticles [42].
