3.2 Occurrence in Nature
33
species of fish. Similarly, the composition of chitin in other aquatic organisms varies
for the different species.
The major issue which is presently limiting a larger commercial exploitation of
the available chitosan resource is the environmental, technical and economics of
scale surrounding its production process. The chitin market is expected to be more
than triple in the next 9 years. The major drivers for this growth are expected to
be the numerous emerging applications of chitin derivatives, especially chitosan, in
the healthcare industry (Future Market Insights 2019). Researchers have presented
a plethora of ways to use chitin; however, the major challenge is the cost of chitin
production both financially and environmentally. There needs to be further research
into more economic yet environmentally friendly means of extracting chitin and
converting it into useful products, thus making the chitin industry an exciting one
in which new opportunities for researchers and businesses lie in the development of
new chitin-based products and discovering new sources of the second most abundant
polymer on the planet.
3.3 Chemistry of Chitin
3.3.1 Structure
The repeat unit of chitin is an acetylglucosamine structure linked by a beta 1-4
linkage between the monomer units. Chitin is a linear long-chain polymer with a
high molecular weight which varies largely depending on factors such as source,
extraction method and extraction conditions and from batch to batch. It is quite
similar to cellulose, except that one of the hydroxyl (–OH) groups of glucose as
seen in cellulose is replaced by an amine group (–NH 2 ) (Kaya et al. 2017). Chitin is
rather unreactive in its native form. However in its derivative forms, it becomes more
reactive and much more useful. One of the most important reactions that is often
required of chitin is the deacetylation reaction. Chitin in its pure form is about 90%
acetylated, and when it is deacetylated to over 60%, it can be classified as chitosan
(Kalut 2008). Thus although deacetylation of chitin results in chitosan, chitin also
has a level of acetylation. A chitosan polymer chain that has up to 10,000 repeating
units will have at least 6000 of these being glucosamine while the other 4000 will be
acetyl glucosamine. The level of acetylation affects the properties of the chitosan. At a
degree of deacetylation of over 98%, we begin to have a chitosan with good solubility
and minimal aggregation. Figure 3.2 shows the structure of a chitin repeating unit.
33
species of fish. Similarly, the composition of chitin in other aquatic organisms varies
for the different species.
The major issue which is presently limiting a larger commercial exploitation of
the available chitosan resource is the environmental, technical and economics of
scale surrounding its production process. The chitin market is expected to be more
than triple in the next 9 years. The major drivers for this growth are expected to
be the numerous emerging applications of chitin derivatives, especially chitosan, in
the healthcare industry (Future Market Insights 2019). Researchers have presented
a plethora of ways to use chitin; however, the major challenge is the cost of chitin
production both financially and environmentally. There needs to be further research
into more economic yet environmentally friendly means of extracting chitin and
converting it into useful products, thus making the chitin industry an exciting one
in which new opportunities for researchers and businesses lie in the development of
new chitin-based products and discovering new sources of the second most abundant
polymer on the planet.
3.3 Chemistry of Chitin
3.3.1 Structure
The repeat unit of chitin is an acetylglucosamine structure linked by a beta 1-4
linkage between the monomer units. Chitin is a linear long-chain polymer with a
high molecular weight which varies largely depending on factors such as source,
extraction method and extraction conditions and from batch to batch. It is quite
similar to cellulose, except that one of the hydroxyl (–OH) groups of glucose as
seen in cellulose is replaced by an amine group (–NH 2 ) (Kaya et al. 2017). Chitin is
rather unreactive in its native form. However in its derivative forms, it becomes more
reactive and much more useful. One of the most important reactions that is often
required of chitin is the deacetylation reaction. Chitin in its pure form is about 90%
acetylated, and when it is deacetylated to over 60%, it can be classified as chitosan
(Kalut 2008). Thus although deacetylation of chitin results in chitosan, chitin also
has a level of acetylation. A chitosan polymer chain that has up to 10,000 repeating
units will have at least 6000 of these being glucosamine while the other 4000 will be
acetyl glucosamine. The level of acetylation affects the properties of the chitosan. At a
degree of deacetylation of over 98%, we begin to have a chitosan with good solubility
and minimal aggregation. Figure 3.2 shows the structure of a chitin repeating unit.