Crayfish, exoskeleton

As an alternative to the chemical process, the fermentation process has been studied for decades for various crustacean shells including crab shells (Jung et al. 2006, 2007, Oh et al. 2007, Jo et al. 2008), shrimp waste (Cira et al. 2002, Xu et al. 2008), crayfish exoskeleton (Bautista et al. 2001, Cremades et al. 2001), scampi waste (Zakaria et al. 1998), and prawn waste (Fagbenro 1996, Shirai et al. 1998). On fermentation of crustaceans, two main portions of protein and organic acid salts are recovered for feed, fertilizer, and chemical reagent purposes. 

Bierkens J, Vangenechten JHD, Van Puymbroeck S, et al. 1986. Effect of Al and humic acids on the 241Am adsorption on the exoskeleton of the crayfish Astacus leptodactylus eschscholtz. Health Phys 50(2) 277-280. 

Sugawara, A., Nishimura, T., Yamamoto, Y., Inoue, H., Nagasawa, H. and Kato, T. (2006) Self-organization of oriented calcium carbonate/polymer composites effects of a matrix peptide isolated from the exoskeleton of a crayfish. Angewandte Chemie International Edition, 45, 2876-2879. 

Chitin is isolated from the exoskeletons of crustaceans (e.g., crabs, lobsters, crayfish, shrimp, krill, barnacles), molluscs or invertebrate animals (e.g., squid, octopus, cuttlefish, nautilus, chitons, clams, oysters, scallops. 

Travis, D.F., 1965. The deposition of skeletal structures in the Crustacea. 5. The histo-morphological and histochemical changes associated with the development and calcification of the branchial exoskeleton in the crayfish Orconectes virilis Hagen. Acta His-tochem., 20 193—222. 

For two freshwater species, the crayfish Pacifastacus leniusculus) and the snail Juga silicula) whole-body concentration ratios of 1.6 and 41, respectively, were obtained when 9.imTc04 was used as a tracer. Tissue distribution data showed that 79-100 % of the crayfish body burden was in the exoskeleton and digestive gland, whereas the soft tissues of the snails contained 82-96 % of the whole-body activity [70]. 

Chitin is a homopolymer of AT-acetyl-D-glucosamine residues and is a major structural component in the exoskeletons of crustaceans, mollusks, arthropods, and the cell walls of numerous fungi and algae. Owing to its widespread presence in both terrestrial and aquatic organisms, chitin is second only to cellulose as the most abundant biopolymer on the Earth (Shahidi and Abuzaytoun, 2005). On a dry weight basis, shrimp, crab, lobster, prawn, and crayfish have been reported to contain between 14% and 35% chitin, while deproteinized dry shell waste of Antarctic krill contains approximately 40% crude chitin (Haard et al, 1994). Crustaceans are the primary sources of chitin used in industry. Chitin can be extracted from shellfish and crustacean waste by mixing with a dilute add to induce demineralization, followed by a deproteini-zation step in a hot alkaline solution (Synowiecki and Al-Khateeb, 2003). 

There are numerous sources of chitin (Fig. 1) and chitosan is obtained by deacetylatmg chitin with a hot alkali solution. Chitin has been found in a wide array of natural sources, namely crustaceans, fungi, yeasts, insects, annelids, nematodes, mollusks, coelenterate, marine diatoms, squid pens, etc. [16-19]. However, chitosan is primarily manufactured from the exoskeleton of crustaceans (crab, shrimp, prawn, lobster, krill, and crayfish) because of its abundant availability as a by-product of food processing [20, 21]. 

In 1975, sulfuric acid was added to an experimental lake in Canada, causing the pH in the lake to drop from 6.8 to 5, which killed many fish species. Shrimp and minnows died at about pH 5.8, followed by the young trout. At pH 5.6, crayfish began to die as their exoskeletons lost their calcium and became infested with parasites. The sensitivities of aquatic organisms to the lowering of pH based on studies in Scandinavian lakes are summarized in Table 35.4. 

Fig. 6 SEM (a,b,e,f), optical microscopy (d), TEM (c) images of a variety of CaC03-based thin-film composites, (a-c) the thin film formed on the chitin matrix in the presence of calcification-associated peptide (CAP-1) extracted from the exoskeleton of a crayfish, (d-f) rodlike mesocrystals formed on the oriented chitin matrices in the presence of PAA. Reprinted with permission from Wiley-VCH. ...

Crustaceans include a range of species, both freshwater (such as crayfish) and marine (such as crabs, shrimps, prawns, and lobsters). These animals have a segmented body, a chitinous exoskeleton, and paired jointed limbs. The portions eaten are the muscular parts of the abdomen and the muscles of the claws of crabs and lobsters. The flesh is characteristically low in fat and high in minerals, with vitamin levels similar to those found in finfish. 

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