CHITOSAN: STRUCTURE, PRODUCTION, PROPERTIES - CHEMISTRY - 2025

The chitosan or chitosan is a polysaccharide obtained from the deacetylation of chitin. Chitin is a polysaccharide that is part of the cell walls of zygomycete fungi, of the exoskeleton of arthropods, of the ketas of annelids and of the perisarcs of cnidarians; For this reason, chitin was formerly known as a tunic.

Chitin and chitosan are complementary compounds: to obtain chitosan, chitin must be present. The latter can also be formed by the combination of nacre, conchiolin, aragonite and calcium carbonate. It is the second most important polymer after cellulose; In addition, it is biocompatible, biodegradable and non-toxic.

Chitosan is a compound that is important in the agricultural industry, in medicine, in cosmetics, in the pharmaceutical industry, in water treatments and in the coating of metals for orthopedic purposes. It is antifungal, antibacterial, antioxidant and is a good receptor for metals, especially in metallurgical landfills.

Structure

Chitan is obtained when the chitin molecule has been completely deacetylated. Chitosan, on the other hand, is left with one acetyl group per unit to replicate.

Obtaining

To obtain chitosan it is necessary to obtain chitin first. Then it is deacetylated (the acetyl molecule that it has in its structure is removed), so that only the amino group remains.

The process begins by obtaining the raw material, which is the exoskeleton of crustaceans, especially shrimp and prawns.

Washing and drying

A washing treatment is carried out to remove all impurities, such as salt and mineral residues that may be embedded in the exoskeleton of the species. The material is dried well and then ground into flakes of about 1mm.

Depigmentation

Next comes the depigmentation process. This procedure is optional and is done with acetone (organic solvent in which chitosan is insoluble), with xylene, ethanol or with hydrogen peroxide.

Decarbonization and deproteinization

The previous process is followed by the decarbonization process; in which HCl is used. Once this process is finished, the deproteinization is continued, which is done in a basic medium using NaOH. It is washed with plenty of water and finally filtered.

The compound obtained is chitin. This is treated with 50% NaOH at a temperature of approximately 110 ° C for 3 hours.

This process allows the acetyl group to be removed from the chitin structure so that chitosan can be obtained. To be packed, dehydration and grinding are carried out until the particle acquires a size of 250 µm.

Appearance of chitin and chitosan after the production process

Properties

- Chitosan is a compound insoluble in water.

- Its approximate molar weight is 1.26 * 10 ⁵ g / mol of polymer, obtained through the viscometer method.

- It has chemical properties that make it suitable for various biomedical applications.

- It is a linear polyamide.

- It has amino groups –NH ₂ and hydroxyl groups –OH reactive.

- Has chelating properties for many transition metal ions.

- With lactic acid and acetic acid it was possible to form very tight chitosan films in which, through the infrared spectrum (IR), no variation was observed in the chemical structure of chitosan. However, when formic acid was used, variations in the structure could be observed.

What is it for?

In analytical chemistry

- Used in chromatography, as an ion exchanger and to absorb heavy metal ions

- It is used in the production of point electrodes for metals.

In biomedicine

Because it is a natural, biodegradable and non-toxic polymer, it is of great importance in this field. Some of its uses are:

- As a hemodialysis membrane.

- In threads for biodegradable sutures.

- In the process of releasing insulin.

- As a healing agent in burns.

- As an artificial skin replacement.

- As a drug-releasing system.

- Generates a regenerative effect on the connective tissue of the gums.

- To treat tumors (cancer).

- In the control of the AIDS virus.

- It is an accelerator of the formation of osteoblasts, responsible for the formation of bones, and the repair of cartilage and tissues.

- It is a hemostatic that favors the interruption of bleeding.

- It is a procoagulant, so in the United States and Europe it is used as an additive in gauze and bandages.

- It is an antitumor that inhibits the growth of cancer cells.

- It works as an anti-cholesterol, since it inhibits the increase in cholesterol.

- It is an immunoadjuvant, because it strengthens the immune system.

In agriculture and livestock

- It is used in coating seeds, preserves them for storage.

- It is an additive for animal feed.

- It is a fertilizer releaser.

- It is used in the formulation of pesticides.

- It is fungicidal; that is, it inhibits the growth of fungi. This process can be in two ways: the compound itself is capable of acting against the pathogenic organism, or it can generate internal stress in the plant that causes it to release substances that allow it to defend itself.

- It is antibacterial and antiviral.

In the cosmetic industry

- In the production of shaving foams.

- In treatments for skin and hair.

- In the production of foams and hair molding lacquers.

In the dietary field

- It works as a slimming agent. It works by trapping fat in the stomach and has a satiating effect (reduces the desire to consume food). However, it has not been approved by the US Food and Drug Administration (FDA).

In the food industry

- As a thickener.

- As a controlled oxidation agent in some compounds and as an emulsifier.

Good adsorbent

The optimum conditions obtained for the effective elimination of contaminants from the effluent of the pharmaceutical industry are pH 6, stirring time 90 minutes, adsorbent dosage 0.8 g, temperature of 35 ° C and a speed of 100 RPM.

The experimental result showed that chitosan is an excellent adsorbent for the treatment of effluent from the pharmaceutical industry.

References

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3. Larez V, C. (2006) Informative article Chitin and chitosan: materials from the past for the present and the future, Advances in Chemistry, 1 (2), pages15-21 redalyc.org
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