Chitin mineralization

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. 

Pretreatment is the chemical extraction of material known or presumed to be from the original organism. It is necessary to remove contaminants that come from the environment, which might be of a very different age. In general, these methods work by purification of stable large molecules (cellulose, collagen, chitin), mineral complexes such as shell, or reduced carbon (in the form of charcoal). With the exception of... 

Chitosan scaffolds were reinforced with beta-tricalciiun phosphate and calcium phosphate invert glass [177]. Along the same line, composites of Loligo beta-chitin with octacalcium phosphate or hydroxyapatite were prepared by precipitation of the mineral into a chitin scaffold by means of a double diffusion system. The octacalciiun phosphate crystals with the usual form of 001 blades grew inside chitin layers preferentially oriented with the 100 faces parallel to the surface of the squid pen and were more stable to hy-... 

Kirchman, D. L., and J. White. 1999. Hydrolysis and mineralization of chitin in the Delaware Estuary. Aquatic Microbial Ecology 18 187-196. 

In the chiton tooth, the organic framework components are synthesized and secreted by the cells into the extracellular space, and there they self assemble. By the time mineralization is about to occur the cells are tens of micrometers away from many of the mineralization sites. They must therefore operate by remote control. The mineralization sites themselves are within a complex chitin framework, the dimensions of which are in the nanometer range. The sea urchin larval spicule represents the exact opposite situation. Mineralization occurs in a vacuole defined by a membrane, and the entire apparatus is within a consortium of fused cells (the syncytium). The membrane of the syncytium tightly surrounds the growing spicule [74], Therefore, it has been proposed that the cells directly control spicule formation. The mineralization vacuole is subdivided by framework proteins. Nothing is known about the structure of the one nucleation site per spicule in the larvae, but in the adult a well-defined location, enclosed within a framework, has been identified as the nucleation site [83]. Dentin formation is intermediate between the two. It is an extracellular process, and the distances between cells or cell processes and mineralization sites are in the range of tens of micrometers or several micrometers respectively. Nucleation occurs within the fibril or at its surface and is associated with a site on the fibril surface some 7 or 8 nm wide [54]. The space available for crystal growth within the fibril is even smaller in one of the dimensions, namely 2 or 3 nm wide. 

Carbonates The precipitation of carbonates by microorganisms is widespread suggesting that microbial carbonate precipitation coupled with silicate weathering could provide a potential sink for CO2 in terrestrial environments (Thompson Ferris, 1990 Verrecchia et al. 1990 Rivadeneyra et al. 1993 Bruand Duval, 1999 Folk Chafetz, 2000 Fujita et al. 2000 Merz-Preip, 2000 Riding, 2000 von Knorre Krumbein, 2000 Warren et al. 2001 Hammes Verstraete, 2002). Manoli et al. (1997) demonstrated that chitin is a substrate on which calcite will readily nucleate and grow. Fungal filaments mineralized with calcite... 

The crustacean cuticle is made of chitin and protein and has an outer tanned epicuticle within which lies a tanned and calcified exocuticle. The thickest layer is the inner endocuticle which is heavily calcified but contains no tanned problems. The inside of the exoskeleton is formed by a membranous layer which is neither tanned nor mineralized but which covers the cellular epidermis. This layer contains a variety of cell types including melanophores and epidermal cells but the secretion of the exoskeleton is mainly performed by the cuticle-secreting cells and the associated intra-epidermal or reserve cells. The exoskeleton is penetrated by tegumental ducts and by pore canals. The first of these carry secretions from glands through the thickness of the cuticle while the latter may consist of 50—90 fine protoplasmic extensions of each cuticle-secreting cell penetrating the exoskeleton at a density of about 4 X 10 pore canals mm". ... 

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