Literature review
7
B- Biological extraction
An alternative method for chitin extraction is the biological method, which involves the use of
microorganisms to degrade the organic matter surrounding chitin.
Enzymatic demineralization:
The enzymatic demineralization of crustacean shells involves the dissolution of mineral and
protein components by organic acids produced by microorganisms, specifically lactic acidproducing bacteria. This reaction occurs when the organic acids react with calcium carbonate,
which is present in the shells, resulting in the precipitation of calcium salts. These salts are
subsequently removed from the culture medium, and the organic salts are separated from the
precipitated material through washing. The precipitated organic salts can then be uti lized as
preservatives and anti-icing agents. (HASAN et al., 2022).
Enzymatic deproteinization:
Enzymatic deproteinization is a process in which various proteases, including alcalase, pepsin,
papain, pancreatin, devolvase, and trypsin, are utilized to remove proteins from raw materials.
These proteolytic enzymes can be obtained from a variety of sources such as plants, microbes,
and animals. By eliminating the need for preliminary processing steps, proteolytic enzymes
reduce processing time and increase efficiency. (AHMED and Ikram, 2017) (HASAN et al.,
2022) (PELLIS et al., 2022).
Fermentation:
Enzymatic chitin extraction can be expensive due to the high cost of enzymes. However, the
cost can be reduced by using a fermentation process to perform deproteinization. Proteolytic
enzymes produced by lactic acid bacteria can be used to hydrolyse proteins in the shells, and
this process is activated by a low pH in the medium. This method has the advantage of allowing
for the recovery of valuable by-products such as proteins, enzymes, and pigments that can be
used in the food industry, thereby adding further value to the overall process. (SANTOS et al.,
2020).
5. Properties of Chitin
Physicochemicalproperties:
Chitin, as a biopolymer, exists as a colorless, crystalline or amorphous powder, is a highly
crystalline material similar to cellulose, and its solubility and reactivity are affected by the
presence of specific functional groups such as -NH2 and -OH. Chitin consists of β-(1,4)-linked
N-acetyl-D-glucosamine units, which provide the material with unique chemical and physical
properties. (CRINI and LICHTFOUSE, 2019).
The presence of -NH2 and -OH groups in chitin makes it more hydrophilic than cellulose. These
functional groups make chitin partially soluble in some polar solvents such as dilute acids,
acetic acid, and certain ionic liquids. The solubility of chitin also depends on its degree of
acetylation, with low levels of acetylation resulting in higher solubility in some solvents.
(THOMAS et al., 2020).
The -NH2 and -OH groups in chitin also make it reactive towards various chemical
modifications. For instance, chitin can undergo deacetylation to produce chitosan, a material
with enhanced solubility and reactivity due to the presence of free amino groups. Additionally,
7
B- Biological extraction
An alternative method for chitin extraction is the biological method, which involves the use of
microorganisms to degrade the organic matter surrounding chitin.
Enzymatic demineralization:
The enzymatic demineralization of crustacean shells involves the dissolution of mineral and
protein components by organic acids produced by microorganisms, specifically lactic acidproducing bacteria. This reaction occurs when the organic acids react with calcium carbonate,
which is present in the shells, resulting in the precipitation of calcium salts. These salts are
subsequently removed from the culture medium, and the organic salts are separated from the
precipitated material through washing. The precipitated organic salts can then be uti lized as
preservatives and anti-icing agents. (HASAN et al., 2022).
Enzymatic deproteinization:
Enzymatic deproteinization is a process in which various proteases, including alcalase, pepsin,
papain, pancreatin, devolvase, and trypsin, are utilized to remove proteins from raw materials.
These proteolytic enzymes can be obtained from a variety of sources such as plants, microbes,
and animals. By eliminating the need for preliminary processing steps, proteolytic enzymes
reduce processing time and increase efficiency. (AHMED and Ikram, 2017) (HASAN et al.,
2022) (PELLIS et al., 2022).
Fermentation:
Enzymatic chitin extraction can be expensive due to the high cost of enzymes. However, the
cost can be reduced by using a fermentation process to perform deproteinization. Proteolytic
enzymes produced by lactic acid bacteria can be used to hydrolyse proteins in the shells, and
this process is activated by a low pH in the medium. This method has the advantage of allowing
for the recovery of valuable by-products such as proteins, enzymes, and pigments that can be
used in the food industry, thereby adding further value to the overall process. (SANTOS et al.,
2020).
5. Properties of Chitin
Physicochemicalproperties:
Chitin, as a biopolymer, exists as a colorless, crystalline or amorphous powder, is a highly
crystalline material similar to cellulose, and its solubility and reactivity are affected by the
presence of specific functional groups such as -NH2 and -OH. Chitin consists of β-(1,4)-linked
N-acetyl-D-glucosamine units, which provide the material with unique chemical and physical
properties. (CRINI and LICHTFOUSE, 2019).
The presence of -NH2 and -OH groups in chitin makes it more hydrophilic than cellulose. These
functional groups make chitin partially soluble in some polar solvents such as dilute acids,
acetic acid, and certain ionic liquids. The solubility of chitin also depends on its degree of
acetylation, with low levels of acetylation resulting in higher solubility in some solvents.
(THOMAS et al., 2020).
The -NH2 and -OH groups in chitin also make it reactive towards various chemical
modifications. For instance, chitin can undergo deacetylation to produce chitosan, a material
with enhanced solubility and reactivity due to the presence of free amino groups. Additionally,