Crustaceans chitin from

Horst, M.N. 1981. The biosynthesis of crustacean chitin by a microsomal enzyme from larval brine shrimp. Jour. Biol. Chem. 256 1412-1419. 

Chitosan Chitosan has a molecular structure similar to cellulose. This material is produced from chitin, which is widely found in the exoskeleton of shellfish and crustaceans. Chitin is the second most abundant natural biopolymer after cellulose. Chitosan is a good adsorbent for all heavy metals. It has been estimated that chitosan can be produced from shellfish and crustaceans at a market price of 15.43 /kg. 

Shell wastes from shrimp, crab, and lobster processing industries are the traditional source of chitin. However, commercial production of chitosan by deacetylation of crustacean chitin with a strong alkali appears to have limited potential for industrial acceptance because of seasonal and limited supply, difficulties in processing, particularly with the large amount of waste of concentrated alkaline solution causing environmental pollution, and inconsistent physico-chemical properties (Chatterjee et ah, 2005). 

Chitosan and its derivatives are the most widely used cationic polymeric excipients. Chitosan consists of (31—>4 D-glucosamine units and is derived by the deacetylation of chitin from insects, crustaceans and fungi. It interacts ionically with the anionic substructures of sialic acid residues on the mucus layer. Chitosans are rapidly hydrated in a low pH environment like the gastric fluid and do not swell above pH levels of 6.5, exhibiting no more mucoadhesion. 

The normal procedure for preparation of chitin from crustacean shells includes the use of NaOH, HC1, and decoloring agents to remove the remaining proteins, calcium, and color, respectively. The chitin that is produced can then be deacetylated with sodium hydroxide to produce chitosan (Tsai et al., 2002). Jaworska and Konieczna (2001) reported that chitosan can be prepared via chemical means using concentrated hydroxides (40-50%) at high temperatures (100-130 °C). 

Carbohydrates, also referred to as saccharides, are polyhydroxyaldehydes or polyhydroxyketones or compounds that can be hydrolyzed to or derived from polyhydroxyaldehydes or polyhydroxyketones. Carbohydrates have many important biological functions— to store and generate energy in animals and plants (glucose, starch, glycogen), as supportive structures in plants (cellulose) and crustaceans (chitin), and as components of cell membranes and nucleic acids. 

Industrial chitin is obtained from marine food production waste, i.e., crustacean shells from shrimp, crab or krill [13,14]. The processing of shrimps for human consumption generates 40-50% of the total mass of marine food production waste, which is considered to be one of the main pollutants in coastal areas, as it is dumped into the sea [15]. A small part of the waste is dried and used as chicken feed [14].The major components (on dry mass basis) of shrimp waste are chitin, minerals, carotenoids and proteins thus, the utilisation of this shell food waste as an alternative source to produce chitin may help solve environmental problems related to waste generation. 

Acosta N., Jimenez C., Borau V., Hetas A., Extraction and characterization of chitin from crustaceans. Biomass Bioenergy, 5,1993,145-153. 

Several excellent reviews and research papers for the production of chitin and chitosan have appeared in various journals, international symposia, and conferences on chitin and chitosan. Most of the published papers emphasized the production of chitin and chitosan from aquatic crustaceans and from... 

A Enzymatic Production of Chitin from Crustacean Shell Waste... 

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]. 

Indeed, the use of biological treatment instead of chemical treatment for the isolation of chitin from crustacean shells as well as for production of chitosan will substantially reduce environmental pollution. The use of chitin deacetylase for the preparation of chitosan polymers and oligomers offers the possibility to develop an enzymatic process that could potentially overcome most of the drawbacks discussed earlier [59]. As shown in Fig. 4, chitin deacetylase (CDA EC 3.5.1.41) catalyzes the hydrolysis of A-acetamido bonds in chitin to produce chitosan. The presence of this enzyme has been reported in several fungi and insect species [60-68]. 

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],... 

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