Chitin or Chitosan are often referred to as a natural biopolymer, the second most abundant after cellulose. In simple terms, biopolymers are naturally occurring (hence “bio”) large molecules, made up of many repeating units or blocks (hence “poly” which means many).

Chitosan is a natural biopolymer derived from Chitin, which is the second most abundant natural polysaccharide after cellulose. Chitin is primarily found in the exoskeletons of crustaceans such as crabs, shrimps, and lobsters, as well as in the cell walls of fungi. To produce chitosan, chitin is subjected to a deacetylation process, which involves the removal of acetyl groups. This process transforms the chitin into chitosan, making it soluble in acidic solutions, unlike chitin which is not.

Chitosan has several unique properties that make it valuable across various industries. It is biodegradable, biocompatible, non-toxic, and has antimicrobial, antifungal, and chelating properties.The primary source of commercial chitosan is the seafood industry, which provides a large amount of chitin-rich shell waste. This makes chitosan an environmentally friendly product by valorizing waste materials. There’s ongoing research to improve the extraction and production processes of chitosan to enhance its properties and increase its applications.

What is Chitosan?

Chitosan is a naturally occurring biopolymer derived from chitin, found in the shells of crustaceans like shrimp and crabs, and also from fungal sources. It is one of the few cationic (positively charged) polysaccharides available in nature, making it unique among biopolymers.

It is composed of glucosamine and N-acetylglucosamine units and is typically characterized by its degree of deacetylation (DDA), which ranges between 70% and 95%. Chitosan becomes soluble in acidic solutions, forming a clear, viscous liquid. Let us quickly understand a bit more about Chitin – the starting raw material for chitosan.

What makes Chitin or Chitosan a Biopolymer?

Chitin is a polysaccharide, and its repeating unit contains N-acetylglucosamine units.

Chitin is a natural polysaccharide biopolymer made of N-acetylglucosamine units, providing structural strength in shells, exoskeletons, and fungal cell walls. The largest commercial source of Chitin are shells of Shrimps, Crabs, Lobsters and insects. It is also naturally found in the cell walls of mushrooms and other types of fungi.

Chitosan is a polysaccharide, and its repeating unit contains glucosamine.

Chitosan is made up of 2 types of sugar units which are “Amino Sugars” –

• Glucosamine (GlcN) → the deacetylated unit
• N-acetylglucosamine (GlcNAc) → the acetylated unit leftover from chitin

Properties of Chitosan

Degree of Deacetylation DDA

This determines the percentage of deacetylation i.e. removal of acetyl groups 

Higher DDA (often 90%+) = More free amine groups = Better solubility in mild acids = More reactive

• High DDA → better antimicrobial activity (good for food coatings, pharma).
• Low DDA → cheaper, less bioactive, used in flocculation, agriculture.

Viscosity

Viscosity in chitosan describes how thick or resistant to flow its solution is. It depends on molecular weight, concentration, and degree of deacetylation. It indicates polymer chain length & interaction in solution. It is measured in solutions (typically 1% in 1% acetic acid).

Viscosity is not a fixed property of chitosan powder itself. It’s a property of its solution, typically measured in 1% chitosan  in 1% acetic acid solution.

• Higher viscosity → higher MW → thicker coatings or gels.
• Lower viscosity → sprayable coatings, easier mixing.

Molecular Weight

MW is the average size of polymer chains. It is measured in kDa (kilodaltons) and affects viscosity and film strength.

• Low MW → better solubility, lower viscosity, easier processing.
• High MW → stronger films, gels, but higher viscosity.

Choose the right grade of Chitosan for your application