36
3 Chitin
For example, the degree of deacetylation of mollusks is different from that extracted
from crustaceans. Chitin properties vary even within the same species. For example,
different types of mushrooms produce chitin with varying fiber length (Ifuku et al.
2011).
3.3.5 Deacetylation
This is where some or all of the acetyl (COOCH 3 ) functional groups attached to the
N-acetylglucosamine units (2-acetamino-2 deoxy-β-D-glucopyranose) are replaced
with a hydrogen leaving behind an amine (–NH 2 ) end group of glucosamine (2amino-2-deoxy-β-d-glucopyranose). This occurs when chitin is reacted with 40–
50% w/v of sodium hydroxide (Kalut 2008). The extent to which this occurs within
the polymer chain is referred to as the degree of deacetylation (DDA).
3.3.6 Molecular Weight
Chitin from the same source can vary significantly in properties depending on the
batch. For example, a study reported molecular weight of chitin extracted from
chemical method as 33,400 g/mol while that from lactic acid fermentation was
967,000 g/mol (Castro et al. 2018). Although through methods such as gel permeation chromatography, chitosan can be separated into different molecular weights
such that high and low molecular weight chitosans are available in the market. Chitosan of high and low viscosity is also available since molecular weight is related to
viscosity.
The molecular weight of chitin plays a very important role in its applicability.
Molecular weight affects properties such as solubility, viscosity of the solution,
mechanical properties of the film or other products produced and its interaction
and reaction with other polymers and materials in either composite forms or reacted
forms and other forms. The higher the molecular weight of chitin and chitosan, the
lower the solubility. However, this ceases to apply at low molecular weight below
2.43 kDa when the short chain does not aid the formation of hydrogen bonding with
the solvent (Roy et al. 2017). Depolymerization of chitin to obtain lower molecular
weight oligomers can be achieved by acid or enzyme hydrolysis.
3.3.7 Depolymerization
Another important reaction of chitin is the depolymerization into monomers. Chitin
can be completely depolymerized into its monomeric form, acetyl glucosamine, or
deacetylated and depolymerized into glucosamine. Glucosamine has become another
3 Chitin
For example, the degree of deacetylation of mollusks is different from that extracted
from crustaceans. Chitin properties vary even within the same species. For example,
different types of mushrooms produce chitin with varying fiber length (Ifuku et al.
2011).
3.3.5 Deacetylation
This is where some or all of the acetyl (COOCH 3 ) functional groups attached to the
N-acetylglucosamine units (2-acetamino-2 deoxy-β-D-glucopyranose) are replaced
with a hydrogen leaving behind an amine (–NH 2 ) end group of glucosamine (2amino-2-deoxy-β-d-glucopyranose). This occurs when chitin is reacted with 40–
50% w/v of sodium hydroxide (Kalut 2008). The extent to which this occurs within
the polymer chain is referred to as the degree of deacetylation (DDA).
3.3.6 Molecular Weight
Chitin from the same source can vary significantly in properties depending on the
batch. For example, a study reported molecular weight of chitin extracted from
chemical method as 33,400 g/mol while that from lactic acid fermentation was
967,000 g/mol (Castro et al. 2018). Although through methods such as gel permeation chromatography, chitosan can be separated into different molecular weights
such that high and low molecular weight chitosans are available in the market. Chitosan of high and low viscosity is also available since molecular weight is related to
viscosity.
The molecular weight of chitin plays a very important role in its applicability.
Molecular weight affects properties such as solubility, viscosity of the solution,
mechanical properties of the film or other products produced and its interaction
and reaction with other polymers and materials in either composite forms or reacted
forms and other forms. The higher the molecular weight of chitin and chitosan, the
lower the solubility. However, this ceases to apply at low molecular weight below
2.43 kDa when the short chain does not aid the formation of hydrogen bonding with
the solvent (Roy et al. 2017). Depolymerization of chitin to obtain lower molecular
weight oligomers can be achieved by acid or enzyme hydrolysis.
3.3.7 Depolymerization
Another important reaction of chitin is the depolymerization into monomers. Chitin
can be completely depolymerized into its monomeric form, acetyl glucosamine, or
deacetylated and depolymerized into glucosamine. Glucosamine has become another