ABSTRACT
Approximately 70% of marine capture sheries are utilized for processing and a considerable quantity of the processed catch remains as wastes (Kim and Mendis 2006). Discards exceed 20 million tons per annum, which is the equivalent of 25% of the total annual production (FAOSTAT 2001). In crustaceans, waste makes up approximately 45% by weight of the shellsh and comprises discarded heads, thorax, claws, and shells (Subangsinghe 1994, Zakaria et al. 1998). These chitinous shellsh wastes are considered hazardous due to their high perishability and high polluting effect if disposed off-shore (Healy et al. 1994). In the sea, chitinous wastes rapidly lead to eutrophication and exert a high biochemical oxygen demand (BOD), while on land, the waste quickly becomes colonized by pathogens and spoilage organisms causing environmental and public health concerns (Islam et al. 2004, Beaney et al. 2005). The European Union, United States, Japan, and other countries have responded to these issues by setting specic maximum limits for biodegradable municipal wastes that may be disposed in landlls and at sea (Knorr 1984, Shahidi and
2.1 Introduction ............................................................................................................................ 11 2.2 Chitin, Chitosan, and Their Oligomers .................................................................................. 12 2.3 Methods of Extraction from Marine Sources ......................................................................... 14
2.3.1 Chemical Extraction ................................................................................................... 14 2.3.2 Enzymatic/Biotechnological Methods........................................................................ 16 2.3.3 Emerging Technologies .............................................................................................. 18
2.4 Conclusions ............................................................................................................................. 19 Acknowledgment ............................................................................................................................. 19 References ........................................................................................................................................ 19
Synowiecki 1991, Healy et al. 2003). This has led to the exploitation of sheries wastes in highvolume, low-value products such as shmeal and sh silage, pet foods, and fertilizers (Choudhury and Gogoi 1995, Choudhury and Bubliz 1996). Since crustacean and mollusk waste streams constitute a rich source of (higher) value-added products such as chitin, protein, pigments, and avor compounds, the full exploitation/bioconversion of this easily accessible resource has attracted much interest. However, the high costs of purication and the production of corrosive wastes associated with traditional industrial methods of extraction have proved problematic (Muzzarelli 1990, Wang and Hwang 2001, Hayes et al. 2008). Proportions of chitin from these sources may vary with season and species but in general, exoskeletons contain 15%–40% chitin, 20%–40% protein, and 20%–50% calcium carbonate, with other components such as pigments, lipids, and other metal salts present as minor components (No and Meyers 1995, Singer and Wooten 2003, Kurita 2006). A list of commercially exploited marine species and their chitin content is shown in Table 2.1. This overview discusses the fundamental aspects of chitin, chitosan, and chitin/chitosan oligosaccharide extraction from these marine sources through chemical, enzymatic, and emerging biotechnological isolation procedures.
