Chitin chemical structure

L. Cardenas, J. Dominguez, C. Quinto, 1. Lopez-Lara, B. Lugtenberg, H. Spaink, G. Radeniaker, J. Haverkamp, and J. Thomas-Oates, Isolation, chemical structures and biological activity of the lipo-chitin oligosaccharide nodulation signals from Rhizobium etii. Plant Mol. Biol. 29 453 (1995). 

Bioconversion of Shellfish Chitin Waste. In the quest of finding ways to utilize tne nutrients m shellfish processing waste, another avenue has been discovered. A process has been developed which bioconverts shellfish chitin to yeast single-cell protein (96-98). The product of this process is a protein-rich material wRTcfT can be used as an animal and aquaculture feed supplement. Since chitin s chemical structure is nearly similar to cellulose, the concept of this process was inspired from the bioconversion... 

How does the chemical structure of chitin differ from that of cellulose and how does this affect structure and properties ... 

FIGURE 2.1 Chemical structure of chitin showing its monomer N-acetyl-D-glucosamine. 

There are many kinds of natural biodegradable polymers. They are classified into three types according to their chemical structures, i.e., polysaccharides, polypeptides/proteins and polynucleotides/nucleic acids. Among them, polysaccharides, such as cellulose, chitin/chitosan, hyaluronic acid and starch, and proteins, such as silk, wool, poly( y-glutamic acid), and poly(e-lysin), are well known and particularly important industrial polymeric materials. 

With the exception of cellulose and chitin, plant polysaccharides are usually hydrated. Hydration often occurs in the crystalline regions as well as in the amorphous areas. When water of hydration is found in the crystallites, it may or may not affect the conformation of the polysaccharide backbone and in most cases, it affects the unit-cell dimensions, while in a few cases, the water appears to have no effect on unit-cell dimensions. The structures of six hydrated neutral polysaccharides will be examined with regards to the state of water of hydration in the structure. It wi 11 be seen that water may occur as columns or as sheets in these structures. The structures that will be discussed are (1 4)-3-p-xylan, nigeran, amylose, galactomannan, (1 3)-3-p-gTucan and (1 3)-s-P-xy1 an. The chemical structures of these polysaccharides are shown in Figure 1. 

FIGURE 3 Chemical structures of important carbohydrates. Glucose (left), cellulose (upper right), and chitin (lower right). 

FIGURE 53.6 Chemical structure of (a) chitin and (b) chitosan, where n stands for the whole numbers signifying the number of monomers present in the polymer. 

A similar position exists with most other polysaccharides. In general, the same chemical structures, produced by prokaryotes and eukaryotes are unlikely to be related in terms of their biosynthesis. Within the eukaryotes, evolutionary relationships may well exist where similar polymers are found in species that are known, from other evidence, to be closely related. Likewise, the present-day pattern of occurrence of a polymer such as chitin may well suggest that a single t3q>e of mechanism exists for its synthesis and that this has persisted in some phyla, but has been lost during the evolution of others. Where a polysaccharide seems to reappear after an evolutionary gap, there is always a question as to whether this is a re-emergence of the old synthetic pathway, or the acquisition of a new one. It should not be forgotten that the relative simplicity of polysaccharide structure does make the latter quite possible, in principle at least. 

Fig. 3.1 Chemical structure of chitin and deacetylated chitin (chitosan)...

Gonzalez, V., Guerrero, C. and Ortiz, U. (2000) Chemical structure and compatibility of polyamide-chitin and chitosan blends. Journal of Applied Polymer Science, 78(4), 850-857. 

Biocomposites are very fascinating materials since they offer characteristics of two or more different materials, in order to have very specific features that would be practically impossible to obtain by every single material of biocomposite. Chitin is an abundant biopolymer obtained from shrimp, insects and some vegetal species. This material is capable to remove some contaminants like fluoride from water. Nevertheless, in order to improve the mechanical characteristics of chitin, in order to be applied in water treatment in real conditions, it must be supported. Polyurethane is a very versatile polymer due to its chemical structure. During its synthesis, interactions between functional groups take place in order to create the urethane group. The synthesis of biocomposite must bear in mind that interaction between compounds is essential to create a mechanical and chemical resistant material. FTIR with ATR analysis was carried out to characterize a biocomposite based on chitin and polyurethane, demonstrating that interaction between them occurs. 

Chitosan is a linear polysaccharide obtained by extensive deacetylation of chitin. It is mainly composed of two kinds of (3(1 — 4) linked structural units viz. 2-amino-2-deoxy-D-glucose andAi-acetyl-2-amino-2-deoxy-D-glucose. The chemical structure of a completely deacetylated chitosan is represented in Fig. 25.1(c). However, since it is virtually impossible to completely deacetylate chitin, what is usually known as chitosan is a family of chitins with different but always low degrees of acetylation. The capacity of chitosan to dissolve in dilute aqueous solutions is the commonly accepted criterion to differentiate it from chitin. 

Chitin, a linear polysaccharide of P-(1 4)-2-deoxy-2-acetamido-D-glucopyranose, is a major polysaccharide found in crustaceous shells and in cell walls of fungi. In its chemical structure, chitin is similar to cellulose, but it is different in that it has an acetamide group instead of a hydroxyl group... 

Uragami et al. 2001). Their properties are closely related to their chemical structures, composition, sequence, DA, and molecular size. An insight into the biological and physiological functions of chitin and chitosan at the molecular level require a precise knowledge on the primary and secondary structures. 

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