Crab shell chitosan

Chitosan, a polymer of j8-(I 4)-linked 2-amino-2-deoxy-D-glucose residues, is formed on deacetylation of chitin. As pointed out already, this polysaccharide takes an extended conformation similar to that of cellulose. Deacetylation of chitin is very easily evaluated in view of the NMR spectra, as illustrated in Fig. 24.5. The three polymorphs of chitosan, ten-don-chitosan (from crab shell), L-2 (from shrimp shell), An-nealed (from crab shell chitosan annealed at 22°C in the presence of water) are easily distinguished, consistent with the data for the polymorphs as obtained by a powder X-ray diffraction data [38, 39]. The observed non-equivalence of two chitosan chains, as viewed from the splittings of the C-1 and C-... 

We now report crab shell chitosan and its derivatives can have a novel function as an activator of plant cells in (a) the callus formation of cabbage leaves, (b) the germination of soybean and Japanese radish seeds, and (c) the field cultivation of Japanese radish seeds. In addition, we will discuss a possible function of plant chitinase and chito-sanase in connection with the wide distribution of these enzymes in plants. 

Figure 8. A proposed model for the molecular interaction of the plant cells with a pathogen or an insect in nature, and artificial activation of plant cells with crab shell chitosan to enhance the plant production. See the text for details. 

Chitosan is the main structural component of crab and shrimp shells. Chitosan contains both reactive amino and hydroxyl groups, which can be used to chemically alter its properties under mild reaction conditions. Al-acyl chitosans were already reported as blood-compatible materials. UV irradiation grafting technique was utilized to introduce obutyrylchitosan (OBCS) onto the grafted SR film in the presence of the photosensitive heterobifunctional cross-linking agent. The platelet adhesion test revealed that films grafted on OBCS show excellent antiplatelet adhesion. 

D., University of Delaware, unpublished data). Since these experiments were carried out with chitosan obtained from crab shells, further experiments with chitosan isolated from Mucor rouxii (47) will prove whether microbially produced chitosans are more effective elicitors for the biosynthesis of certain phytochemicals than those obtained from marine organisms. 

Chitosan Natural (crab shells) Deacetylation of chitin Soluble in aqueous solutions (low pH), insoluble in organic solvents... 

FIGURE 2.10 XRPD patterns for (A) a-chitin from different sources (1) brown shrimp shells, (2) pink shrimp shells, (3) crabs shells, and (4) crayfish shells (B) the corresponding chitosan. 

In the area of renewable materials, bulk oxypropylation of chitin and chitosan has been performed. Chitin and chitosan are abundant natural polymers obtained from shellfish, such as crab shell or shrimp shell. This solvent free reaction yields viscous polyols. Unfortunately, propylene oxide homopolymer is formed as a by-product but is easily separated. It should be noted that care was taken to minimize the risk involved in the use of toxic, flammable propylene oxide (the reagent in this process). 

Coughlin, R.W., Deshaies, M.R., and Davis E.M., Chitosan in crab shell wastes purifies electroplating wastewater. Environ. Prog., 9, 35, 1990. 

Chitin A natural polysaccharide obtained from crab shells The chain is based on acetylated glucosamine units the natural polymer can be converted to the acid-soluble partially deacetylated product chitosan... 

Chitosan is a natural glucosamine polymer obtained from crab shells. The polymer retains Cu(II) more strongly than does cellulose. It was used in LEC of amino acids, peptides, and enzymes. 

The ultrasonic degradation of Chitosan (deacetochitin, found in crab shells) was studied by another research group [35], Chitosan was degraded in acetic acid at 60 °C under ultrasonic irradiation. The viscosity of the Chitosan decreased by 80% after irradiation for 15 h, compared with 55% decrease by reflux under acid condition for 24 h. This was taken as evidence that the degradation under sonication is faster, purer, and more complete than under conventional conditions. 

The use of chitosan as a means of controlling the release of amino-acids has been also investigated by Rhone-Poulenc (ref. 5). Chitosan (deacetylated chitin) is extracted from shrimp and crab shells. It is known as a non-toxic, biodegradable polymer (Fig. 5). It is insoluble in water at neutral pH and has the capacity to dissolve at low pH values. Chitosan solutions are prepared by dissolving the polymer in dilute acetic acid. Stearic acid and oleic acid are the hydrophobic constituents in the chitosan-based coatings. 

Chitosan, derived from crab shell chitin, is —80% deacetylated. It is dissolved in 1 M HO Ac (5 g/L) and freeze dried to yield a white, soft material. The chitosan is washed with 0.9 M A-methylmorpholine (NMM) in DMF followed by DMF. The Rink linker (0.4 mmol) is dissolved in 6 mL of DMF containing N-[(17/-benzotriazol-1 -yl)(dimethylamino)methylene]-A-methyl-methanaminium tetrafluoroborate A-oxide (TBTU) (0.3 M), HOBt (0.3 M), and NMM (0.4 M) and added to 150 mg (dry weight) of chitosan. The mixture is incubated at 45°C for 1 h, washed with DMF, and the chitosan capped with acetic anhydride-dry pyridine (1 1, v/v) for 1 h at 45°C. This procedure yields Fmoc-linker substituted chitin (Fig. 16). After drying in vacuo, the degree of substitution is determined by measuring the Fmoc released after treatment of a sample with piperidine-DMF (3 7) for 30 min at room temperature. Typically, chitosan substitution levels are 0.08-0.35 mmol/g. 

The underlying chitin matrix in the crab shell and its microfibrillar structure is shown in Fig. 3.4. This chitin is termed as a-chitin because of its crystal stmcture. Treatment of this chitin with 20 % NaOH for 1-3 h at 120 °C gives a 70 % deacetylated chitin (chitosan), which is soluble in many dilute acids. The detailed method is given in Sect. 3.4. The repetition of this step can give deacetylation... 

Yen, M., Yang, J., Mau, J. Physicochemical characterization of chitin and chitosan from crab shells Carbohydr. Polym. 75, 15-21 (2009)... 

After cellulose, it is the second most abundant natural polymer found in the nature. Figure 8.9 shows the exoskeleton structure of crab shells, where chitin was derived. Chitin can also be synthesized artificially through chitinase-catalyzed polymerization of a chitobiose oxazoline derivative. Chitosan, a very important derivative of chitin, is obtained... 

In bacterial fermentation for chitin and chitosan production, the most often applied strains are Lactobacillus sp., Bacillus sp., Pseudomonas sp and S. marcescens. The microbial DP process is little efficient, ranging between 50% and 85% DP rate depending on materials, used microorganism, fermentation type, and time. Rao et al. (2000) cultured shrimp biowaste with L. plantarum and achieved 75% DP. Bautista et al. (2001) achieved 81.5% DP from crayfish using Lactobacillus pentosus 4023. Fermentation of crab shell wastes with 10% S. marcescens FS-3 inoculum resulted in DP of 84% and DM of 47% at 7 days culture (Jo et al. 2008). Squid pen for the preparation of P-chitin were deproteinized by 73% for 3 days with Bacillus sp. TKU004 (Wang et al. 2006). Also, the shrimp shells were deproteinized by 75% and 87% at 30°C for 6 days with Candida parapsilosis and Pseudomonas maltophilia, respectively (Chen 2001). 

Chitosan is usually prepared by the deacetylation of chitin. The conditions used for deacetylation will determine the molecular weight and the degree of deacetylation. Chitin is found in the exoskeleton of some arthropods, insects, and fungi. Commercial sonrces of chitin are the shell wastes of crab, shrimp, lobster, etc. Proteins present in shrimp or crab shells are removed by alkaline treatment with 3%-5% NaOH (w/v) aqueous solution at room temperatnre overnight. Other inorganic constituents that remain in the products are removed by alkaline treatment with [3%-5% NaOH (w/v)]... 

Evans, J.R., Davids, W.G., MacRae, J.D., and Amirbahman, A. 2002. Kinetics of cadmium uptake by chitosan-based crab shells. Water Res. 36 3219-3226. 

---