Chitin is a naturally occurring substance found in animals and plants. It’s a linear polysaccharide of β-1,4-linked N-acetylglucosamine units with α-(1→4)-linked 2,3-diaminohexane side chains. The strength of Chitin lies in its versatility: it can be made into films that are stronger than Kevlar; it can be used to make new antibiotics or as a cancer treatment; and it is the most abundant organic molecule on earth. These are just some of many uses that have been discovered so far.
Chitin is a long-chain polysaccharide of alternating units of N-acetylglucosamine (GlcNAc) and 3,6-anhydro-α-(1→4)-linked D-glucosamine. It is the second most abundant renewable polysaccharide after cellulose, but may be the most abundant biopolymer on earth. The structure of chitin is similar to that of cellulose.
Chitin was first described in 1811 by French chemist Anselme Payen, who isolated it from shells, called it “fungus cellular substance” and believed that it was composed of some type of carbohydrate. In 1865 American physician John Elliot and Scottish-born chemist Alexander Graham Bell synthesized chitin from the fermentation broth of a fungus. By 1875, George Washington Carver had found that chitin could be used to make numerous products. It was in the 1880s that chemists began to work with chitin at length. Most notably, the German chemist Hans Ehrlich isolated new compounds from chitin in 1889 and developed a process to produce industrial quantities of it.
The first refineries started production in 1890, followed by a flourishing of industry around 1900. Chitin is a natural biomaterial found in many different organisms. Despite its widespread occurrence, few people know what chitin does or how it functions.
Before we discuss what chitin is, let’s get one thing out of the way first: contrary to popular belief, chitin is not a type of plastic. The word "chitin" is derived from the Greek word "χίτυνος" (khitinos), meaning shell or skin. This should make it clear that chitin is not a synthetic material but a natural one.
It’s also important to note that chitin is not the same thing as cellulose, even though both materials are commonly found in plants and fungi. Chitin, if you remember your high school biology, is a polysaccharide, while cellulose is a polymer – two different things.
So, what is chitin? Chitin is a polymer that gives rigidity to the cell walls of fungi and the exoskeletons of arthropods. The presence of this material in plant cell walls is debatable: while some scientists believe that chitin may be present in plant cell walls – at least as an epiphenomenon – most are convinced that the principal polysaccharide material in plants’ cell walls is cellulose.
Chitin is a linear polymer composed of units of N-acetylglucosamine (GlcNAc). The polymer is, in its free form, somewhat similar to cellulose in that it consists of linear chains of sugar (or sugar derivatives) molecules that are held together by hydrogen bonds.
The difference between chitin and cellulose is the fact that cellulose’s hydroxyl groups are completely bound to neighboring hydroxyls, while in chitin the hydrogen bonds are not all equally strong. This allows the polymer chains to slide over each other to a certain extent. The fact that chitin can slide over itself gives it its unique mechanical properties: when force is applied to the material, it tends to rearrange itself so as to minimize any external forces acting upon it.