Today, chitin and chitosan are being used in a wide range of areas. In medicine,
they are used as absorbent stitching fibers, ingredients in artificial skin, and wound
treatments. They are used in cosmetics for their outstanding hydration efforts; in
wastewater treatment as wastewater coagulants and heavy metal absorbents; in
health food to boost immunity and combat cancer; and in paper-making, textiles,
agriculture, and other industries.
The first industrial production of chitin and chitosan occurred in Japan in 1970.
In South Korea, an estimated 4 million tons are produced each year. On its own,
chitin has few uses; in most cases, it is used as an ingredient in the manufacturing of
chitosan. As seen in Fig. 8.29, many different chitin and chitosan lysates can be
produced, each of them with different physiological functions. Recent years have
seen the discovery of new functions in low-molecular-weight monosaccharides and
chitin and chitosan oligosaccharides obtained from chitin and chitosan hydrolysis.
These are performing a crucial role in maximizing use of as yet unexploited chitin
and chitosan (Prashanth and Tharanathan 2007).
Similarly, active research is also being conducted to use chitin-degrade enzymes
such as chitinase and chitosanase to produce molecules with low molecular weight.
This section will consider the chitin and chitosan obtained from the shells of crabs,
shrimp, and other crustaceans and the production and uses of their oligosaccharides (Kim 2018).
A. How Are Chitin and Chitosan Produced?
Chitin and chitosan are extracted from the shells of crabs and shrimp. These shells,
however, consist of proteins, lipids (pigments), carbohydrates (chitin), and minerals
(calcium carbonate), and carbohydrates extracted from them may be either chitin or
chitosan. Chitin and chitosan both consist solely of carbon (C), hydrogen (H),
oxygen (O), and nitrogen (O)—elements that bond with each other in the thousands
or tens of thousands according to specific rules.
To produce chitin alone from a crab shell, one must first remove the mineral
calcium carbonate (CaCO 3 ) component. Hydrochloric acid (HCl) is used to remove
it according to the following principle.
When combined with an acid such as hydrochloric acid, calcium carbonate (also
known as limestone) produces calcium chloride (CaCl 2 ) and carbonic acid
(H 2 CO 3 ). In this case, the calcium chloride and carbonic acid can be easily
removed, the former because it dissolves in water and latter because it is broken
down by the powerful hydrochloric acid and water and carbon dioxide. Once the
calcium carbonate is removed, the material can be immerse in thin sodium
hydroxide (NaOH) solution to break down the proteins and pigments; once these
are removed, chitin is produced (Fig. 8.29 (b)) (Lee et al. 2003).
After cellulose, chitin is one of the most quantitatively abundant materials in the
natural world. The fundamental reasons for our failure to take advantage of it
concerns the lack of solvents to readily dissolve it and its weak reactivity. Its use
has begun to increase with the discovery of numerous functions as chitosan is
produced from chitin and the substance is dissolved in weak organic acid obtains
greater reactivity. Chitosan is a form in which the N-acetyl group (CH 3 CO
− ) is
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8 Developing Functional Materials with Marine Organisms
they are used as absorbent stitching fibers, ingredients in artificial skin, and wound
treatments. They are used in cosmetics for their outstanding hydration efforts; in
wastewater treatment as wastewater coagulants and heavy metal absorbents; in
health food to boost immunity and combat cancer; and in paper-making, textiles,
agriculture, and other industries.
The first industrial production of chitin and chitosan occurred in Japan in 1970.
In South Korea, an estimated 4 million tons are produced each year. On its own,
chitin has few uses; in most cases, it is used as an ingredient in the manufacturing of
chitosan. As seen in Fig. 8.29, many different chitin and chitosan lysates can be
produced, each of them with different physiological functions. Recent years have
seen the discovery of new functions in low-molecular-weight monosaccharides and
chitin and chitosan oligosaccharides obtained from chitin and chitosan hydrolysis.
These are performing a crucial role in maximizing use of as yet unexploited chitin
and chitosan (Prashanth and Tharanathan 2007).
Similarly, active research is also being conducted to use chitin-degrade enzymes
such as chitinase and chitosanase to produce molecules with low molecular weight.
This section will consider the chitin and chitosan obtained from the shells of crabs,
shrimp, and other crustaceans and the production and uses of their oligosaccharides (Kim 2018).
A. How Are Chitin and Chitosan Produced?
Chitin and chitosan are extracted from the shells of crabs and shrimp. These shells,
however, consist of proteins, lipids (pigments), carbohydrates (chitin), and minerals
(calcium carbonate), and carbohydrates extracted from them may be either chitin or
chitosan. Chitin and chitosan both consist solely of carbon (C), hydrogen (H),
oxygen (O), and nitrogen (O)—elements that bond with each other in the thousands
or tens of thousands according to specific rules.
To produce chitin alone from a crab shell, one must first remove the mineral
calcium carbonate (CaCO 3 ) component. Hydrochloric acid (HCl) is used to remove
it according to the following principle.
When combined with an acid such as hydrochloric acid, calcium carbonate (also
known as limestone) produces calcium chloride (CaCl 2 ) and carbonic acid
(H 2 CO 3 ). In this case, the calcium chloride and carbonic acid can be easily
removed, the former because it dissolves in water and latter because it is broken
down by the powerful hydrochloric acid and water and carbon dioxide. Once the
calcium carbonate is removed, the material can be immerse in thin sodium
hydroxide (NaOH) solution to break down the proteins and pigments; once these
are removed, chitin is produced (Fig. 8.29 (b)) (Lee et al. 2003).
After cellulose, chitin is one of the most quantitatively abundant materials in the
natural world. The fundamental reasons for our failure to take advantage of it
concerns the lack of solvents to readily dissolve it and its weak reactivity. Its use
has begun to increase with the discovery of numerous functions as chitosan is
produced from chitin and the substance is dissolved in weak organic acid obtains
greater reactivity. Chitosan is a form in which the N-acetyl group (CH 3 CO
− ) is
278
8 Developing Functional Materials with Marine Organisms