Chitins water-soluble

In concentrated NaOH, chitin becomes alkali chitin which reacts with 2-chloroethanol to yield 0-(2-hydroxyethyl) chitin, known as glycol chitin this compoimd was probably the first derivative to find practical use (as the recommended substrate for lysozyme). Alkali chitin with sodium monochloroacetate yields the widely used water-soluble 0-carboxymethyl chitin sodium salt [118]. The latter is also particularly susceptible to lysozyme, and its oUgomers are degraded by N-acetylglucosaminidase, thus it is convenient for medical appHcations, including bone regeneration. 

Another polysaccharide system that has received considerable interest is the chitosans which are water soluble derivatives of chitin. These materials appear to be very biocompatible and degradable and so are potentially excellent candidates as polymeric drug systems (27). 

Poly(HASCL) depolymerases are able to bind to poly(3HB)-granules. This ability is specific because poly(3HB) depolymerases do not bind to chitin or to (crystalline) cellulose [56,57]. The poly(3HB)-binding ability is lost in truncated proteins which lack the C-terminal domain of about 60 amino acids, and these modified enzymes do not hydrolyze poly(3HB). However, the catalytic domain is unaffected since the activity with water-soluble oligomers of 3-hy-droxybutyrate or with artificial water-soluble substrates such as p-nitrophenyl-esters is unaffected [55, 56, 58, 59]. Obviously, the C-terminal domain of poly(3HB) depolymerases is responsible and sufficient for poly(3HB)-binding [poly(3HB)-binding domain]. These results are in agreement ... 

Chitosan is a polymer produced from hydrolysis of natural chitin. Chitosan is not readily soluble in aqueous solutions, but can be solubilized and is thus considered with other water soluble polymers. In the hydrophobic form, chitosan has been treated in a similar manner to other hydrophobic polymers with microparticles produced by emulsion and phase separation techniques. Microparticles can be taken up by the gastrointestinal lining in a manner similar to that discussed for other hydrophobic microparticles. 

There are also several water-soluble mixtures of polysaccharides, including those derived from seaweeds and marine animals, such as gum arabic, agar, algin, carrageenan, and chitin. These are hydrophilic. Their suspensions in water can be quite viscous and can readily form gels, and they can form viscous interfacial films around dispersed droplets and bubbles [821], They are used to stabilize suspensions, foams, and emulsions and are used in many different foods and medicines including, for example, ice cream [428,430], See also Ref. [822],... 

Chitin is the naturally occurring, insoluble acetylamino derivative of cellulose yielding the polycation chitosan when deacetylated (with concentrated NaOH and heat). Chitosan is water-soluble in proportion to the degree of deacetylation. 

Difficulties are encountered in carrying out controlled, partial hydrolyses of chitin because of the need to use concentrated acids to dissolve the polysaccharide. Chitosan (de-A -acetylated chitin), however, is water-soluble and amenable to controlled hydrolysis. Using ion-exchange chromatography, a chitosan hydrolyzate has been fractionated to give at least five saccharides, the first two of these having been characterized as 2-amino-2-deoxy-D-glucose hydrochloride and chitobiose hydrochloride. > Fractionation of chitosan hydrolyzates on oarbon-Celite was only successful after selective A-acetylation and then it yielded the first seven members of a series of chitin saccharides, the properties of which clearly indicate the... 

Chitosan is insoluble in water, concentrated acids, alkalis, alcohol, and acetone, but dissolves readily in dilute acids. Water-soluble salts of chitosan include the nitrate and the perchlorate. As described on p. 377, formation of chitosan sulfate and the color reaction of chitosan with iodine have been widely used as qualitative tests for the detection of chitin. Nitration of chitosan with a mixture of acetic and nitric acids or with absolute nitric acid enabled both the free ester and its nitrate salt to be isolated. The perchlorate salt of this ester was also prepared, but it was unstable. Chitosan can be W-acetylated to give products similar to chitin except for their greatly reduced chain-length W-formyl-, iV-propionyl-, JV-butyryl-, and iV-benzoyl-chitosan were also prepared. ... 

Carboxymethyl-chitin (CM-chitin), as a water-soluble anionic polymer, is the second most studied derivative of chitin after chitosan. The carbox-ymethylation of chitin is imdertaken in a similar manner to that of... 

Storage/metabolic carbohydrate (cold and hot water soluble) 22 7 13 35 1-2 5-30 8 60 (chitin)... 

Smoke condensates are obtained by condensing smoke in water or another solvent. They may be further fractionated, purified or concentrated. The fractionation steps have two purposes to obtain products of interesting olfactory properties and to reduce the concentration of undesirable by-products from the smoke. Only the water-soluble fraction is used. The organic phase will be abandoned because a work up of the tar fraction is too expensive. The smoke solution will be filtered in order to remove polycyclic aromatic hydrocarbons (PAHs). According to a Russian patent [18] it is also possible to use 2% chitin and 0.5% chitosan for removing PAHs almost quantitatively. Afterwards the components of the smoke solution may be concentrated by distillation. The resulting product will be processed into smoke flavouring preparations. 

Many water-soluble polysaccharides can be induced to orient themselves in a single direction by annealing and pulling spun fibres in a certain direction, and many natural linear polymers (such as cellulose or chitin) are biosynthesised partly crystalline. 

The solubility problems associated with chitin and chitosan may limit their use in physiological and functional foods. The intestines of most animals lack the ability to produce chitinase and chitosanase. These two enzymes have the ability to hydrolyze chitin and chitosan, respectively. Therefore, they will be excreted unchanged in the feces. On the other hand, chitin and chitosan oligomers are considered to have more physiological functions because they are water soluble and their solutions are less viscous, so they are readily absorbed in the human intestine (Jeon et al., 2000). 

Heux et al. (2000) found that after partial deacetylation (<50%), the product of chitin becomes soluble in acidified water. Therefore, chitosan is characterized by its DA, which is the average mole fraction/percentage of A-acetyl-D-glucosaminc units within the macromolecular chain (Desbrieres, 2002). Alternatively, Heux et al. (2000) calculated DA by measuring all carbonyl or methyl groups divided by the integral of all the carbon atoms in the backbones. The DD may be determined by a titration method in which chitosan is dissolved in 0.1% acetic acid to form a 0.01% solution. This is followed by titration with 0.0025 N poly (vinyl sulfate) potassium salt (PVSK) with 1% toluidine blue (TBO) as an indicator. The acetyl content of... 

Suzuki, S. 1996. Studies on biological effects of water soluble lower homologous oligosaccharides of chitin and chitosan. Fragrance J. 15, 61-68. 

Tokura et al.49 synthesized a polyamide of the Perlon type (40) starting from a 6-O-carboxymethyl-D-glucosamine derivative as monomer.This compound was obtained by carboxylmethylation of chitin with monochloroacetic acid, followed by hydrolysis of the glycosidic linkage. Hie molecular weight (Mw 15,000) of the resulting water-soluble polyamide 40 was determined by gel-permeation chromatography and electrophoresis (Scheme 11). 

The synthesis of chitin was increased by the addition of water-soluble chitodextrins to the reaction mixture the cellodextrins of highest degree of polymerization had the greatest effect. These oligosaccharides were shown to function as acceptors for the 2-acetamido-2-deoxy-D-gluco-pyranosyl groups. The reaction may, therefore, be expressed as follows. 

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