No reference chitin exists yet, but the overall quality of marketed chitosans

improved sharply during the last few years: chitosans of various grades

(technical, food and cosmetic, pharmaceutical and medical)

are today commercially available.

A chapter prepared for

Chitin and Chitosan: Opportunities and Challenges

P.K. Dutta, ed.

SSM International Publ., Contai, Midnapore, India.

2005

Foreword by Riccardo A.A. Muzzarelli

Besides being the only largely abundant cationic polysaccharide, chitin is the most abundant nitrogen compound: its degradation makes nitrogen available to countless living organisms. Oligomeric lipochitins are produced by Rhizobium in root nodules of leguminous plants, while performing nitrogen fixation from the atmosphere. Chitin, then, is indispensable to life in general.

There is no economical advantage in isolating chitin per se: chitin becomes available simply because there is a market for the crustaceans meat. However, just a minor fraction of the huge resources of chitin-bearing raw materials, coming from the crustacean meat canning factories, is today being processed into chitin for technical purposes.

The countries where crustaceans are abundant face a variety of difficulties in converting freshly isolated crab, shrimp and lobster shells into chitin: for example in Norway the conformation of the coasts (deep fiords, transportation difficulties, widely scattered landing locations) prevented for long time the industrial exploitation of the resources, but as soon as the activities were rationally organized, the industrial production of chitosan started.

Of course each country has to solve its own specific technological, ecological, economical and political problems. The Falkland Islands war between Argentina and United Kingdom years ago led to the termination of the krill chitosan production, because it prevented the use of the Polish fishing bases and facilities on those islands.

The quality of chitins and chitosans vary with origin, fishing season, type of handling of raw materials and equipment used. Chitins and chitosans are being used to produce dietary supplements, efficient wound dressings, confortable textiles, drug carriers, functional cosmetics, safe preservatives for meat and fruits, and various technical items for the protection of the environment.

Chitin nanofibrils

A Chapter by Riccardo A.A. Muzzarelli and Corrado Muzzarelli

This chapter directs attention to the chitin crystallites otherwise called whiskers i.e. highly crystalline chitin nanofibrils. While they have been isolated by various research teams many years ago, the purpose has always been the analytical study of their structure, and behaviour of their suspensions. During the last few years, however, some indications appeared in the literature about the preparation of composites made of chitin whiskers dispersed into natural and artificial polymers. It is felt that this subject represents at this time an opportunity for a better exploitation of chitin, as well as a challenge in view of certain technical difficulties.

Figure. Structure of alpha-chitin: (a) ac projection; (b) bc projection; (c) ab projection. The structure contains a statistical mixture of 2 conformations of the –CH₂OH groups. Reprinted from Progress in Polymer Science 31. Rinaudo M. Chitin and chitosan: properties and applications. Pages 603–632. Copyright (2006), with permission from Elsevier.

Figure. Structure of anhydrous beta-chitin: (a) ac projection; (b) bc projection; (c) ab projection. A major point of difference from alpha-chitin is the absence of hydrogen bonds in the b direction Reprinted from Progress in Polymer Science 31. Rinaudo M. Chitin and chitosan: properties and applications. Pages 603–632. Copyright (2006), with permission from Elsevier.