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.
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).
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