Chitin alkaline deacetylation

Chitosan, the most abundant marine mucopolysaccharide, is derived from chitin by alkaline deacetylation, and possesses versatile biological properties such as biocompatibility, biodegradability, and a non-toxic nature. Due to these characteristics, considerable attention has been given to its industrial applications in the food, pharmaceutical, agricultural, and environmental industries. Currently, chitosan can be considered as a potential marine nutraceutical because its remarkable biological activities have been investigated and reported, in order to exploit its nutraceutical... 

In the more abundant a chitin the chains in alternate sheets have opposite orientations,101102 possibly a result of hairpin folds in the strands. Native chitin exists as microfibrils of 7.25 nm diameter. These contain a 2.8-nm core consisting of 15-30 chitin chains surrounded by a sheath of 27-kDa protein subunits. The microfibrils pack in a hexagonal array, but the structure is not completely regular. Several proteins are present some of the glucosamine units of the polysaccharide are not acetylated and the chitin core is often calcified.103 The commercial product chitosan is a product of alkaline deacetylation of chitin but it also occurs naturally in some fungi.102 Chitin is also present in cell walls of yeasts and other fungi. It is covalently bonded to a P-l,3-linked glycan which may, in turn, be linked to a mannoprotein (see Section D,2)97... 

Figure 11. Relationship of carbon-to-nitrogen content of chitin subjected to alkaline hydrolysis for varying lengths of time, v, idealized chitin (0% deacetylation, N-aeetyl-D-glucosamine, M.W. = 203) a, idealized chitosan (100 deacetylation, glucosamine, M.W. = 161). (Reproduced with permission from Ref. 12 Copyright 1984, Academic Press.)...

Chitosan is a linear cationic polysaccharide made up of copolymers of glucosamine and A-acetylglucosaminc. It is commercially obtained by alkaline deacetylation of chitin [53, 68] and has been used for the nasal delivery of a number of drugs. The usefulness of chitosan in the enhancement of nasal absorption was reported first by Ilium [69]. Later, Ilium and his group also published experimental results indicating that solution formulations with 0.5% chitosan promoted the absorption of nasally administered insulin in rat and sheep [70]. 

We used the crosslinked chitosan fiber (hereafter called ChF) in this experimental study. ChF was fabricated by Fuji Spinning Co., Japan. Fig.l shows the unit molecular structure of chitosan which was transformed from chitin by deacetylation. Chitin is a natural biopolymer which is contained in the shell of arthropods. Chitosan was crosslinked to make an adsorbent with acid, alkaline, and chemical proofs. The fabrication method of ChF was presented elsewhere.[S,6]. 

Polysaccharide Containing Polymers. Chitosan (Table 7.3-1) is composed of 2-amino-2-deoxy p-D-glucan and is prepared from naturally occurring chitin via alkaline deacetylation. Unlike other cationic polymers chitosan is nontoxic and biodegradable, making it an ideal candidate for therapeutic applications. Although the density of positive charges of chitosan is lower than for other cationic polymers. 

Chitosan, a natural-based polymer obtained by alkaline deacetylation of chitin, is nontoxic, biocompatible, and biodegradable. These properties make chitosan a promising candidate for conventional and novel drug delivery systems. Because of the high affinity of chitosan for cell membranes, it has been used as a coating agent for liposome formulations [43-45]. 

Chitosan is a linear copolymer composed of N-acetyl-D-glucosamine and D-glucosamine units [Fig. 16.4). It is derived from alkaline deacetylation of chitin that is the second most abundant polysaccharide next to cellulose [Fig. 16.4) [Sloan, 1992). Chitin is the main component in the shells of crustaceans such as shrimp, crab, and lobster. It is also found in the exoskeleton of mollusks and insects, and the cell walls of some fungi [Rlnaudo, 2008 Raabe et al., 2007 Vincent and Wegst, 2000). 

Chitosan is a versatile polycationic biopolymer derived from alkaline deacetylation of chitin. It exhibits several valuable inherent properties such as antibacterial, antifungal, antiviral, antacidity, chelation, non-toxicity, and biodegradability as well as properties such as film formation. Further, due to its possession of hydroxyl and amino functional groups, chitosan can be fabricated to tailor... 

A CHT specimen (company Chimme , Russia) obtained by alkaline deacetylation of crab chitin was chosen as the object of investigation. To prepare CHT film specimens semi-diluted (2g/dl) solutions were made by dissolving a dry polymer weight at room temperature for 8-10 hr. Acetic acid with the concentration of 170 g/dl was used as the solvent. 

One of the most studied biosorbent is chitin, which is an abundant biopolymer found in crustaceans, insects and fungus. This biopolymer is commercially purified by alkaline deproteinization, acid demineralization and decoloration by organic solvents of crustaceans wastes (Pastor, 2004). An additional stronger alkaline treatment of chitin produces deacetylated chitin. If the acetylation degree (DA) decreases at 39% or less, the biopolymer is named chitosan. Hence, the DA of chitin is variable and depends on the process conditions (alkali concentration, contact time, temperature, etc.), which produces DA values from 100 to 0%. Because of this, chitin is known as the biopolymer which has a DA from 100 to 40% likewise, when the chitinous biopolymer has DA lower than 40%, the biopolymer is named chitosan. Chitosan is, therefore, a biopolymer with structure very similar to that of chitin (see Figure 2) however, chitosan solubility is much greater, especially in acid mediums. 

Another material that has been added to PVA to produce a composite cryogel is chitosan. Chitosan is obtained from chitin by alkaline deacetylation. It is a cationic polysaccharide, and has been proposed as a good material for addition to the PVA matrix for cryogel composite production in order to enhance protein absorption [79]. Due to the hydrophilicity of PVA, cell adhesion proteins are not able to absorb, preventing cell adhesion [79]. Because of this, work to create a more favorable environment for cell growth while still maintaining the beneficial mechanical properties of the PVA cryogel structure is important for certain applications. 

Chemically chitosan is obtained from the alkaline deacetylation of chitin from the exoskeleton of crustaceans (eg, crabs, shrimp.), forming a-l,4-linked 2-amino-2-deoxy-a-D-glucose (A-acetylglucosamine Fig. 10.3) [5]. 

Chitosan is a water-insoluble, nontoxic, edible, biodegradable polymer (polysaccharide) that is obtained commercially from chitin by alkaline deacetylation [103]. Chitosan is the second most abundant biopolymer in nature after cellulose. Since chitosan is a polycationic polymer, its high sensitivity to moisture limits its applications. One way to overcome this drawback is to blend the material with humidity resistant polymers such has PLA. Suyatma et al. [104] combined hydrophilic chitosan with hydrophobic PLA (92% L-lactide and 8% mesolactide, Mw = 49,000 Da) by solution and film mixing, resulting in improved water barrier properties and decreased water sensitivity of the chitosan films. However, testing of mechanical and thermal properties revealed that chitosan and PLA blends are incompatible. 

Broadly, the three different steps involved in the preparation of chitin from crustacean shells can be classified as demineralization, deproteinization and decoloration, which is then followed by its alkaline deacetylation for the synthesis of chitosan [10,11]. Briefly, the outer crustacean shells are initially removed from the shrimps and crabs and washed with cold water, dried in the sun and demineralized with 1.25 N HCl at room temperature. The shells are then washed with water to remove acid and calcium chloride. They are then deproteinated by boiling with 5% sodium hydroxide (NaOH) for 15 min. This process of deproteinization is repeated to completely remove the protein content from the shells and then washed with water to neutrality. It is then decolorized with acetone to remove the remaining pigments and the resultant product is chitin, which is then dried imder the sun [12,13],... 

LDPE 10803-020 (90,000 molecular weight, 53% crystallinity degree, and 0,917 g/sM density) and chitosan samples of Bioprogress Ltd. (Russia) obtained by alkaline deacetylation of crab chitin (deacetylation degree 84%), and 115,000 were used as components for producing biodegradable polymer films. 

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