3.5 Extraction of Chitin
43
3.5.4 Extraction of Chitin from Insects
Although insects are not exclusively aquatic organisms, they can be found in aquatic
areas either surrounding stagnant water or releasing their lava on the water. Some
aquatic insects such as the dragonfly start life as aquatic larvae form for many years
before they move out of the water and fly. These tend to spend most of their life in
water, and their life as adults is relatively short (Berg 2009). Making use of the cuticle
of insects for chitin production is a potential solution to sustainable pest control or
simply making use of an easily cultivated abundant source of chitin.
Chitin extraction from insect is a relatively recent development. A few insect
species have been found to contain chitin; these include desert short-horned grasshoppers, green bugs, German cockroach, vespid wasp and yellow jacket wasp (Badawy
and Mohamed 2015). To extract chitin from insects, the first step is to kill the insects
by freezing or dead insects could be collected. This is then followed by deproteinization with potassium hydroxide at 40 °C for 48 h. The deproteinized mass is then
washed repeatedly with distilled water until neutral. The next stage is then to remove
the mineral content using acid for this, and 5% acetic acid is used. The use of acetic
acid is favorable as it allows use of acid from a sustainable and non-fossil-based
source as acetic acid can be produced through fermentation. Dehydration is then
carried out with ethanol by series.
Other studies have extracted chitin from bumble bee (Majtan et al. 2007) and beetles (Liu et al. 2012) using the conventional sodium hydroxide deproteinization and
hydrochloric acid demineralization. The structure of chitin in terms of demineralization, crystallinity and molecular weight varies for different species of insects. Some
studies nonetheless report similarities between the chitins extracted from insects to
the commercial chitin (Liu et al. 2012). There is yet to be a defined taxonomic classification of chitin from various species; however, it is concluded in the different
studies that the chitin obtained from insect has similar characteristics to those from
aquatic sources.
3.5.5 Microbial Extraction
Certain microbes are able to metabolize the proteinous parts of the chitin sources,
while the acidic condition generated by the acids created by the microbes dissolves
the minerals leaving behind a solid crude chitin which can then be further processed
and purified to obtain chitin. The obtained chitin can then be further deacetylated
to obtain chitosan. The fermentation process achieves partial deproteinization and
demineralization. This is then followed by further chemical treatment to obtain purer
chitin. Although some acids and alkali are still used in this process, it is at a much
lower concentration since most of the demineralization and deproteinization are
achieved during the fermentation process. Up to 99.6% and 95.3% of deproteinization
and demineralization have been achieved, respectively, from lactic acid fermentation
43
3.5.4 Extraction of Chitin from Insects
Although insects are not exclusively aquatic organisms, they can be found in aquatic
areas either surrounding stagnant water or releasing their lava on the water. Some
aquatic insects such as the dragonfly start life as aquatic larvae form for many years
before they move out of the water and fly. These tend to spend most of their life in
water, and their life as adults is relatively short (Berg 2009). Making use of the cuticle
of insects for chitin production is a potential solution to sustainable pest control or
simply making use of an easily cultivated abundant source of chitin.
Chitin extraction from insect is a relatively recent development. A few insect
species have been found to contain chitin; these include desert short-horned grasshoppers, green bugs, German cockroach, vespid wasp and yellow jacket wasp (Badawy
and Mohamed 2015). To extract chitin from insects, the first step is to kill the insects
by freezing or dead insects could be collected. This is then followed by deproteinization with potassium hydroxide at 40 °C for 48 h. The deproteinized mass is then
washed repeatedly with distilled water until neutral. The next stage is then to remove
the mineral content using acid for this, and 5% acetic acid is used. The use of acetic
acid is favorable as it allows use of acid from a sustainable and non-fossil-based
source as acetic acid can be produced through fermentation. Dehydration is then
carried out with ethanol by series.
Other studies have extracted chitin from bumble bee (Majtan et al. 2007) and beetles (Liu et al. 2012) using the conventional sodium hydroxide deproteinization and
hydrochloric acid demineralization. The structure of chitin in terms of demineralization, crystallinity and molecular weight varies for different species of insects. Some
studies nonetheless report similarities between the chitins extracted from insects to
the commercial chitin (Liu et al. 2012). There is yet to be a defined taxonomic classification of chitin from various species; however, it is concluded in the different
studies that the chitin obtained from insect has similar characteristics to those from
aquatic sources.
3.5.5 Microbial Extraction
Certain microbes are able to metabolize the proteinous parts of the chitin sources,
while the acidic condition generated by the acids created by the microbes dissolves
the minerals leaving behind a solid crude chitin which can then be further processed
and purified to obtain chitin. The obtained chitin can then be further deacetylated
to obtain chitosan. The fermentation process achieves partial deproteinization and
demineralization. This is then followed by further chemical treatment to obtain purer
chitin. Although some acids and alkali are still used in this process, it is at a much
lower concentration since most of the demineralization and deproteinization are
achieved during the fermentation process. Up to 99.6% and 95.3% of deproteinization
and demineralization have been achieved, respectively, from lactic acid fermentation