Chitin isolation

Chitin is classically a linear polymer of /3-d-(1 - 4)-linked 2-acetamido-2-deoxy-D-glucosyl residues. However, after comparing chitin isolated from different sources, it became evident that substantial variations in solubility, molecular weight, acetyl values, and specific rotation occur among samples. It would appear that chitin is not a single, polymeric entity, but rather, a family of closely related products derived from natural chitin-protein complexes.209... 

M. Zhang, A. Haga, H. Sekiguchi, S. Hirano, Structure of insect chitin isolated from beetle larva cuticle and silkworm (Bombyx mori) pupa exuvia, Int. J. Biol. Macromol. 27 (2000) 99-105. 

Figure 25.2 Schematic representation of the different steps involved in chitin/chitosan preparation procedures. In this diagram a second treatment with dilute NaOH is considered for chitin isolation in order to remove any residual protein.

Chitin isolation processes are generally performed through the following consecutive steps raw material conditioning, protein extraction (deproteinization), removal of inorganic components (demineralization) and decolouration. This sequence is preferred if the isolated protein is to be used as food additive for livestock feeding. Otherwise, demineralization can be carried out first [10]. A brief account of these processes will be given below. A more detailed description of chitin isolation (and chitosan preparation) can be found elsewhere [5, 8, 11]. 

Chen, H. C. 2001. Microbial deproteinization for chitin isolation. In T. Uragami, K. Kurita, and T. Fukamizo (eds.), Chitin and Chitosan, pp. 165-169. Kodansha Scientific Ltd. Tokyo, Japan. 

In the past, a small quantity of shell waste was utilized for animal feed or chitin isolation [19]. Thus, the processing of shellfish was a major concern for environmental pollution. Nowadays, this problem has been overcome to a certain extent... 

The absence of chitin in the endosternite (an internal skeletal support from prosomal muscles) of chelicerates has been noted. There is some evidence that chitin isolated from crayfish (Astacus fluviatilis) is bound covalently to protein. ... 

Soy protein chitin Isolated soy protein/chitin blends plasticized with glycerol chitin improved modulus and strength 1064... 

Keywords Chitin isolation, demineralization, deproteinization, natural whiskers. 

For a review of the isolation of chitin from natural sources and some of its uses see the November 1990 issue of the Journal of Chemical Education (pp 938-942)... 

Nikkomycins. The nikkomycins (141—159), isolated from S. tendae are nucleoside-peptide antibiotics (1,4,244,245) as shown in Table 8. Nikkomycins X and Z are stmcturaHy identical to neopolyoxins A and C, respectively. Compound (141) is a competitive inhibitor of chitin synthetase. Two new nikkomycins, nikkomycin pseudo-Z and pseudo-J (158, 159), contain a C-glycosidic bond between C-5 of uracil and C-1 of... 

Amino-sugars and Related Compounds. Part IV. Isolation and Properties of Oligosaccharides Obtained by Controlled Fragmentation of Chitin, S. A. Barker, A. B. Foster, M. Stacey, and J. M. Webber, J. Chem. Soc., (1958) 2218 - 2227. 

Isolated chitins are highly ordered copolymers of 2-acetamido-2-deoxy-/3-D-glucose and 2-amino-2-deoxy-j6-D-glucose. The occurrence of the latter is explained by the fact that in vivo chitin is covalently finked to proteins via the nitrogen atom of approximately one repeating unit out of ten, therefore upon isolation a degree of deacetylation close to 0.10 is found. Chito-biose, 0-(2-amino-2-deoxy-j6-D-glucopyranosyl)-(l 4)-2-amino-2-deoxy-... 

Many years ago chitin was seen as a scarcely appeahng natural polymer due to the variety of origins, isolation treatments and impurities, but the works of several analytical chemists and the endeavor of an increasing number of companies have qualified chitins and chitosans for sophisticated applications in the biosciences. Chemistry today offers a range of finely characterized modified chitosans for use in the biomedical sciences. Moreover, surprising roles of these polysaccharides and related enzymes are being unexpectedly discovered [351]. 

Fig. 2. Spectrum of anionic isoperoxidases isolated from potato (a) crude protein extract, (b) protein fraction not adsorbed on chitin, and (c) chitin-specific peroxidises. M - protein markers.

Therefore, the ability of certain POs to bind with chitin is a widespread phenomenon and -possibly - connected with the defence reactions of the organisms to pathogen attacks. Since it was shown that some biogenic molecules - such as chitooligosaccharides or salicylic acid -can activate an anionic POs, we might suggest that an application of these compounds optimises the process of anionic PO isolation with a chitin. 

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). 

This conclusion10 has been reached mainly from crystallographic studies on chitin and on acetylchitobiose obtained from chitin by acetoly-sis.107 The chitobiose was isolated in the form of its crystalline octa-acetate which could also be obtained108 by acetylation of the hydrolyzate produced by the action of fuming hydrochloric acid on chitin. A hen-decaaeetylchitotriose also was obtained by this procedure. 

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