Sources of Chitin and Chitosan

The molecular weight of chitosan is another important property that determines its suitability for a particular application. It determines the viscosity of its solution and the strength of chitosan fiber and film. The molecular weight of chitin and chitosan depends on its source and deacetylation conditions [time, temperature, and concentration of NaOH], respectively [1, 4]. Molecular weight of chitosan determined by various methods such as viscometry [28], gel permeation chromatography [29] and light scattering spectrophotometry [30]. 

The increasing relevance of chitin and chitosan as sources of a variety of remarkable mataials is highlighted in Chapter 25, dealing with these animal polysaccharides. The possibility of their transformation into liquid polyols arose a decade ago in the context of the search for a film forming polymer electrolyte [14]. Figure 12.6 gives the FTIR spectra of chitosan before and after oxypropylation. 

The degree of acetylation (or deacetylation) and the molecular mass are undoubtedly the most important parameters to establish the chemical and physical identity of chitin and chitosan. Both parameters vary with the biological source of the raw material and the preparation method. They also dictate the physicochemical, functional and biological properties of these polysaccharides, essential to fit an application or end product. Solubility, pK, viscosity, gelling capacity, among other properties, are all dependent on these parameters. 

Therefore, this article reviews the recent development of the production process of chitin and chitosan from insects, terrestrial crustaceans, and mushrooms. Moreover, the possibility for the large-scale production of chitin and chitosan from these sources are discussed. 

By studying the organic matrix of mushroom (Figure 1.3), it can be considered that the major problem in the extraction of chitosan from mushroom source is that chitin/chitosan is complexed or intertwined with glucan or other polysaccharides. Consequently, the extraction of chitin and chitosan from the resultant suspension is difficult and the yield of chitin and chitosan is very low. However, the knowledge in this area is very limited and it is necessary to solve more problems other than the particular problem mentioned above to reach the final goal of chitosan production from mushroom. 

Based on the present knowledge on this topic, the mycelium of basidiomycetes can be considered an alternative source for the production of chitin and chitosan that might be useful for some specific practical applications. Mushroom chitosans have a degree of deacetylation of 70%-90% that depends on mushroom species and treatment conditions, and average molecular weight about 1-2 x 10 Da (Crestini et al. 1996, Pochanavanich and Suntomsuk 2002, Yen and Mau 2007a, Mario et al. 2008). 

Abdou, E.S., Nagy, K.S.A., and Elsabee, M.Z. 2008. Extraction and characterization of chitin and chitosan from local sources. Bioresour Technol. 99 1359-1367. 

These two key production concerns of chitin and chitosan when managed properly can be the springboard for chitin and chitosan research to be set on a level playing field. This can only energize research interactions globally and establish chitin and chitosan as one biopolymer isolated solely from biological sources that can match synthetic polymers as biomaterials with defined purity characteristics. 

As stated above, the present biomedical products utilize only the base materials. Chanical derivatization is the way forward to realize the fuU potential of chitin and chitosan (Alves and Mano 2008). The well-known C6-earboxymethyl-chitin and ehitosan would be an ideal starting place (Raimunda and Campana-Filho 2008). However, this work again started with the alkali-chitin process that is known to be ineffieient and associated with inhomogeneity eoncems. Another recent work is the preparation of Af-hydroxyacryl-chitosan that utilizes ehitosan from a commercial source without further treatment (Maa et al. 2008). Phosphorylated chitins and ehitosans are another example of chemical derivatization that yields soluble compounds (Jayakumar et al. 2008). 

Written by 40 international contributors who arc leading experts in the field of natural biomaterials, this book provides an overview of the sources and production of chitin and chitosan derivatives. It also covers their... 

There are many standard operating procedures available for extraction of chitin and chitosan because of their wide ranges of sources [39-45]. Although lots of work... 

Keeping in mind the importance of chitosan, as well as its economic value as an industrial product, we must pay attention to its key physical parameter, i.e., turbidity. Depending on source, a marked difference is observed in aqueous solutions of chitosan and its derivatives in terms of their turbidity [33]. Turbid aqueous solutions of chitosan and chitosan-derived products greatly lose their commercial value. Such chitosan cannot be used as a commercial product and in some cases may have to be discarded. Therefore, the selection of source plays a pivotal role in the production of chitin and chitosan. Shepherd et al. [20] reported the production of chitosan from New Zealand Arrow squid Notodarus sloani) pens as well as the evaluation of the functional properties of this squid chitosan compared with chitosan extracted from crustacean sources. Squid pen chitin and chitosan were visibly cleaner than chitin and chitosan obtained from crab and crayfish. In addition, due to the lower mineral content of squid pen as compared to cmstacean shells, the demineralization process can be skipped to extract chitin, which also makes the production cheaper. As shown in Table 4, the squid pen chitosan is similar in... 

Because the properties of chitin straightforwardly and inherently depend on the source of chitin, it is necessary to characterize the properties of chitin before it is further utilized for a specific application. In fact, not every chitin or chitosan sample can be used for the same applications. That is why a complete characterization of the samples is mandatory. The physicochemical characteristics of chitin and chitosan and the determination methods are summarized in Table 8. 

Chitin and chitosan are natural products, commercially available from many sources as mentioned previously. It is usually found in the presence of proteins, calcium carbonate, and perhaps other polysaccharides. Thus, its quality ranges from crude extracts to high purity material. Many of the properties of chitin and chitosan are dependent on the degree of deacetylation. The distribution ofAT-acetyl groups in these polymers is also expected to have an influence on the properties. 

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