Chitin

CHITIN

Biological Source

It is a nitrogenous polysaccharide consisting of amino and acetyl group found in the exoskeleton of the tarantula. Its a tough semitransparent horny substance—the principal component of the exoskeletons of arthropods and the cell walls of certain fungi. This is the dense substance forming the indigestible outer skeleton of insects, and the material from which the walls of the mycelia are made. This product can be found in crustaceans, such as crabs, lobsters, and shrimp. It can also be found in insects, worms, and fungus or mushrooms. Depending upon the different place and different creatures the percentage of chitin content varies.

History

Chitin was first found in Mushrooms in 1811 by Professor Henri, which was later to be called Chitin. During 1830s, it was isolated from insects and named Chitin. The name chitin is derived from Greek meaning tunic or envelope. During 1850s, Professor C. Roughet discovered while experimenting with Chitin that it could be transferred into water-soluble form through some chemical reaction and in late 1870s name Chitin modified to Chitosan and later on much of the research was focused on these compounds.

Preparation

The shells are made into fine powder and treated with 5% hydrochloric acid for 24 h to remove the impurities and calcium present in the shell. The above extract is then treated with proteolytic enzyme like pepsin for the removal of protein from the shell. The product is then bleached with acidified hydrogen peroxide for 4–6 h. It is then deacetylated at 120°C with a mixture containing two parts of potassium hydroxide, one part of ethyl alcohol and one part of ethylene glycol. The process of deacetyla-tion is continued till the test for acetylisation gives report of minimum acetyl content. This deacetylated product is known as the chitosan.

Solubility

Insoluble in water, dilute acid, alcohol and organic solvents, Soluble in sulphuric acid and hydrochloric acid.

Chemical Constituents

Chitin mainly consists of the aminosugar N-acetylglu-cosamine, which is partially deacetylated. The mostly deacetylated form of chitin is called chitosan. Chitin is present in nature usually complexed with other polysaccharides and with proteins.

Chemical Test

A Chitosan is soaked in iodine solution and to it add 10% sulphuric acid. It gives deep violet colour.

Chitosan is dissolved in 50% nitric acid and crystallized for the formation of spherecrystals of chitosanitrate. The crystals when observed under polarized light using crossed nicol, a distinct cross is observed.

Uses

It is used in wound healing preparations, cuts and burns. It is in medicine that the bacteriostatic, immunologic, antitumoral, hemostatic and anticoagulant properties of chitin and its derivatives have been of the greatest use. Due to its biocompatibility with human body tissue, the cicatrizant properties of chitin has demonstrated their effectiveness for all forms of dressings-artificial skin, corneal bandages and suture thread in surgery, as well as for implants or gum cicatrization in bone repair or dental surgery. In dental creams, it keeps the paste healthy and regenerates gums that are in poor condition.

Chitin is also used as a sizing agent for rayon, cotton, wool and even for synthetic fibres. It has adhesivity to glass and plastics. Industrially chitin is used in the process of water treatment by separating organic compounds and heavy metals, and for treating sewage by precipitating certain anionic wastes and capturing pollutants such as DDT and PCBs (polychlorobenzene).