Crab shells are rich in a natural resource, namely chitosan.
Chitosan (chitosan), also known as deacetylated chitin, polyglucosamine, soluble chitin, is a biological macromolecule with molecular weight of 120,000~590,000 transformed from chitin by deacetylation reaction, which has various physiological functions such as biodegradability, biocompatibility, non-toxicity, anti-bacterial, anti-cancer, lipid lowering and immune enhancement.
Since Braconot described chitin in 1811, the development history of chitin and chitosan has been more than 100 years.
Structural characteristics
Chemical name: β-(1→4)-2-amino-2-deoxy-D-glucose
Molecular formula: (C6H11NO4)n
Molecular weight of the monomer: 161.2
Glucosamine is the basic component unit of chitosan, chitosan is the sugar unit of the basic structure of chitosan, and the end product obtained by natural degradation of chitosan using chitosanase is chitosan.
Physical properties.
The solubility of chitosan is related to the degree of deacetylation, relative molecular mass and viscosity, the higher the degree of deacetylation, the smaller the relative molecular mass and the more soluble in water; the lower the degree of deacetylation, the larger the relative molecular mass and the greater the viscosity. Chitosan has good adsorption, film-forming, permeability, fibrillation, hygroscopicity and moisturizing properties. Deacetylation degree and viscosity (average relative molecular mass) are the two main performance indicators of chitosan.
An important index affecting the performance of chitosan – degree of deacetylation
Degree of deacetylation (DD) is the ratio of the number of deacetylated glucosamine units to the total number of glucosamine units, and it is one of the most basic structural parameters for investigating chitosan/chitosan. The degree of deacetylation has a significant effect on the solubility, viscosity, ion exchange capacity and flocculation properties of chitosan. Usually, chitosan with more than 55% N acetyl removed can be soluble in 1% acetic acid or hydrochloric acid and is called chitosan, but chitosan with deacetylation degree above 70% can only be used as a useful industrial product.
Chitosan with deacetylation degree of 55%-70%, 70%-85%, 85%-95%, 95% -100% are called low deacetylated chitosan, medium deacetylated chitosan, high deacetylated chitosan and ultra high deacetylated chitosan respectively, and it is extremely difficult to prepare chitosan with 100% deacetylation degree.
Application Direction
1.Food industry.
As immobilized enzyme carrier
Microcrystalline chitosan, chitosan acetate solution is sprayed into the alkali solution for solidification, and chitosan micro-particles are obtained by separation and regeneration, which can be used as the carrier of immobilized enzymes, and the enzymes immobilized by chitosan can be used in sugar production, wine making, vinegar making, protein hydrolysis and other biological preparation projects.
Used as food additive
Microcrystalline chitosan as food thickener and stabilizer can be used in the production of condiments such as mayonnaise, peanut butter, sesame paste, canned corn paste, cream substitute, etc. Usually, vinegar often produces precipitation after long storage, which is mainly due to the formation of macromolecular complexes between metal ions and tannins and other phenolic acids. The vinegar treated with chitin and chitosan has not precipitated even after one year of storage. When producing soy sauce, adding appropriate amount of chitosan can remove protein and prevent precipitation. Adding a small amount of chitosan in soy sauce can appropriately reduce the amount of salt added and the product will not deteriorate in long-term storage.
Used as food packaging film
Chitosan, starch and water are mixed evenly to make film, and then treated with alkali after drying, it can be made into chitosan-starch synthetic food packaging film, which is non-toxic, edible, oil resistant, insoluble in cold and hot water, high tensile strength, and can be used for packaging solid, semi-solid and liquid food, the film can automatically biodegrade, so there is no white environmental pollution.
Used in food preservation and preserving
Chitosan can be used in vegetable preservation, meat preservation, seafood preservation, starch, soybean products preservation and egg, milk and soybean products preservation.
2.Daily use chemicals.
Chitosan is non-toxic, tasteless and has antibacterial effect. It can be added into cosmetics to improve the film-forming property of products, with antibacterial and moisturizing functions, and does not cause any allergic irritation. Various shampoo and hair care products made with chitosan have the effect of easy combing, hair fluffiness, fullness and bright hair color. It is more effective for thin hair that is prone to breakage and split ends.
In Europe, the United States, Japan and other countries and regions have hundreds of daily cosmetics containing chitosan for sale.
3.Pharmaceutical industry.
National Pharmacopoeia (Part IV) stipulates that chitosan is used as pharmaceutical excipients, disintegrants, thickeners, etc.
Carrier material
Using chitosan as drug carrier can stabilize the ingredients in the drug, promote drug absorption, delay or control the dissolution rate of the drug, help the drug reach the target organ, and anti-acid, anti-ulcer, and prevent the drug from irritating the stomach.
Film-forming materials
Chitosan can be used as film-forming materials for film agents, preparation of oral film agents, Chinese medicine film agents, etc.. The size of its relative molecular weight has a prominent impact on the film-forming properties and membrane properties, usually the lower the molecular weight, the lower the tensile strength of the membrane, the stronger the permeability. Suitable cross-linking agents can be selected to improve the strength of the membrane and change the barrier properties of the membrane.
Thickening agent
When chitosan is used as thickening agent, the solution viscosity increases with increasing concentration; when the concentration is high, the viscosity of the concentrated solution shows thixotropy. When the temperature increases, its viscosity decreases, and the law is consistent with the general flow law of concentrated solutions of polymers.
Targeted formulation materials chitosan and its derivatives can be used as targeted formulation materials.
Its structural units contain hydroxyl, amino and other functional groups, which can be used to connect extracellular or intracellular targeting ligands, thus building targeted drug carriers for targeted drug delivery therapy. There are many targeted formulation dosage forms using chitosan as carrier material, mainly nanoparticles and microspheres.
Other applications
Chitosan can be used as a filler and flavoring agent for tablets. Chitosan has good biocompatibility and biodegradability, and the degradation products can be absorbed by human body, do not accumulate in the body, no immunogenicity, and can be made into absorbable surgical sutures.
