Shrimp Waste Contributes to Environmental Pollution

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Processing of large bulk of fish, shrimp and other aquatic organisms produces a corresponding large bulk of by-products and wastes. Much of these wastes are made into various value-added products, while considerable quantities are discharged as the processing effluents with large volume of waters used in processing. Fish and shrimp processing effluents are very high in biological oxygen demand, chemical oxygen demand, total suspended solids, fat-oil-grease, pathogenic and other microflora, organic matters and nutrients. Fish and shrimp processing effluents are, therefore, highly likely to produce adverse effects on the receiving coastal and marine environments. Although substantial reduction of the waste loads is possible through application of available simple techniques, due to lack of proper managerial and regulatory approaches this is not in practice in most part of the world. About 40% of the oyster shell waste is dumped in the coastal region causing serious environmental problems (Lee et al. 2005).

Chitinous waste produced commercially from sea food processing is a major environmental threat. Demineralisation and deproteination require large amounts of acid and soda and, thus, a lot of fresh water. The de-acetylation of chitin to generate chitosan requires even larger amounts of soda and, in addition, a lot of energy to heat the process. Alternative ways of chitin isolation and chitosan generation are required to extract these biopolymers without undue environmental stress. In the fishing industry, crab shells have always been treated as common waste, which, at best, was considered suitable for livestock feed or was used in agriculture as an inexpensive, natural nitrogen fertilizer. The effectiveness of crab shells as fertilizer has gained importance in present day agriculture due to the fact that the shells are broken down by enzymes, and the acetylglucosamine units of chitin hinder the development of fungi and nematodes in soil (Jaszkowski 2001). The possible utilization of chitin rich waste (Fig. 6.1) would fetch two major benefits in the countries where seafood is processed on an industrial scale. Apart from decreasing pollution, the chitooligosaccharides produced during the process contribute enormously to the field of biotechnology. However, the production of chitin and its hydrolyzed derivatives, such as acetylglucosamine and chitooligosaccharides from waste of the shellfish industry, has been limited due to the high cost of chitinase and expensive pretreatment processes of the shrimp and crab shell (Cosio et al. 1982). Therefore, the exploitation of chitinases produced by chitinolytic bacteria for efficient bioconversion of chitinous waste has gained tremendous importance. Soil bacteria are excellent sources of chitinases and could be used for catabolic conversion of chitinous waste into useful molecules for application in agriculture, biotechnology and medicine (Kishore et al. 2005b; Bhattacharya et al. 2007).

Chitin Application

Fig. 6.1 Schematic diagram showing the possible utilization of chitin waste for production of N-acetylglucosamine and chitooligosaccharides. Chitin waste could be deproteinized by treating with proteolytic enzymes to obtain raw chitin. Physical methods of pretreatment of chitinous waste enhances further enzymatic or chemical degradation. Raw chitin or shrimp/crab shells can be subjected to physical force such as grinding and milling in a converge mill (Nakagawa et al. 2011). In the enzymatic degradation, chitin degrading enzymes viz. exo- or endo-chitinases along with auxiliary helper proteins efficiently convert chitin waste to useful oligomers and dimers. Random cleavage of polymeric chitin by endochitinases gives mostly chitooligomers. while the action of exochitinases gives rise to dimers that are further cleaved by chitobiase resulting in monomers. End products of endo and exo enzymes (oligomers and N-acetylglucosamine) have wider applications in various industries as detailed in the text

Fig. 6.1 Schematic diagram showing the possible utilization of chitin waste for production of N-acetylglucosamine and chitooligosaccharides. Chitin waste could be deproteinized by treating with proteolytic enzymes to obtain raw chitin. Physical methods of pretreatment of chitinous waste enhances further enzymatic or chemical degradation. Raw chitin or shrimp/crab shells can be subjected to physical force such as grinding and milling in a converge mill (Nakagawa et al. 2011). In the enzymatic degradation, chitin degrading enzymes viz. exo- or endo-chitinases along with auxiliary helper proteins efficiently convert chitin waste to useful oligomers and dimers. Random cleavage of polymeric chitin by endochitinases gives mostly chitooligomers. while the action of exochitinases gives rise to dimers that are further cleaved by chitobiase resulting in monomers. End products of endo and exo enzymes (oligomers and N-acetylglucosamine) have wider applications in various industries as detailed in the text

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