Scientific background

institute for environmantal technology EUTEC
Prof. Dr. M. Schlaak, Dr. W. Lindenthal
FH Oldenburg/Ostfriesland/Wilhelmshaven, Constantiaplatz 4, 26723 Emden

The idea

It is reported that prawn fishermen have healthy teeth because they chew the freshly cooked prawns on their way.

Mainly the prawn shell consists of chitin, a hard shell. Chitin can chemically be transformed to chitosan.

In the past years some busy activities took place in the area of the chitosan research

The article of D. Schanzenbach (2000) shows an overview of chitin and chitosan.
 

What is chitin / chitosan?

Chitin is a relative of cellulose, both are β-1,4 compound gluco-configured homopolymers. Chitin contains an acetamido-group instead of the hydroxy-group with cellulose.

Chitosan differs from chitin by the presence of free amino-groups. The transformation into chitosan is done by deacetylisation of the acetamido-group. Completely deacetylised chitosan has no N-actyl-groups (ill. 1):

Chitin :

Chitosan :

Ill. 1: Structure of chitin and chitosan

Natural chitin has a medium molecular mass of 1 – 2 x 106 Dalton and thus chain length of 6000-12000 mono-saccharide units. Chitosan has a low-medium molecular mass as during the transformation some chains are split.
 

Occurrence

Chitin is the main part of the shell substance of the arthropoda, that means of the chelicerata, insects and crustaceans, but it is present in mushrooms and with some further kinds of the invertebrates.

The annual regeneration of chitin amounts to 2,3 * 109 t. The share of usable chitin of the pure biomass is approx. 106 – 107 tons.

For the production of chitin and chitosan most of the waste of the food industry of the shrimps is used: shells of the shrimps occurring during shelling them.

 

Production

Chitin is produced by removing the flesh remains from the shells of the shrimps. Then the Ca-combinations in the shells have to be removed giving the shell its hardness.

The transformation to chitosan is usually chemical. An enzymatical transformation is still in the research stage.

 

Properties of chitin and chitosan

Chitin is relatively resistant against mechanical and chemical influences.

Chitosan can be characterized by the following:

 

Features being important for the use in a toothpaste.

 

Use of chitin / chitosan

Numerous applications are discussed in literature:

 

Literature:

T. Becker, “Ionenaustauscher auf Chitosan-Basis”, Dissertationsschrift, 1998

A. Domard, E. Piron, „Recent approach of metal binding by chitosan and derivatives, Adv. Chitin Sci. 4, 295 – 301, 2000

E. Guibal, C. Milot, J. Roussy, “Chitosan-gel beads for metal recovery”, in Chitin Handbook, R.A.A. Muzzarelli et. al., Grottamare, 423 – 429, 1997

M. Ishihara, “Photocrosslinkable Chitosan Hydrogel as a Wound Dressing and a Biological Adhesive”, Trends in Glycoscience and Glycotechnology,Vol.14 No.80 (November 2002) pp.331–341

R.A.A. Muzzarelli, R. Rocchetti, “Enhanced capacity of chitosan for transition-metal ions in sulphuric acid solutions”, Talanta Vol. 21, 1137 – 1143, Pergamon Press, 1974

H.J. Park, S.T. Jung, J.J. Song, S.G. Kang, P.J. Vergano, R.F. Testin, “Mechanical an barrier properties of chitosan-based biopolymer film, Kichin, Kitosan Kenkyu 5, 19 -26 [Chem. Abstracts 131, 20503], 1999

C. Remunan-Lopez, R. Bodmeyer, “Mechanical and water vapour transmission properties of polysaccharide films, Drug Dev. Ind. Pharm. 22, 1201 – 1209, 1996

H. Sano, T. Matsukubo, K. Shibasaki, H. Itoi, Y. Takaesu, “Inhibition of adsorption of oral Streptococci to saliva treated hydroxiapatite by chitin derivatives”, Bull. Tokyo dent. Coll., Vol. 32, No. 1, 9 – 17, 1991

D. Schanzenbach: „Chitin und Chitosan“, Praxis der Naturwissenschaften-Chemie, 6/49, 2000

R. Tarsi, R.A.A. Muzzarelli, C.A. Guzmàn, C. Pruzzo, „Inhibition of Streptococcus mutans, Adsorption to Hydroxoapatite by Low-molecular-weight Chitosans”, J. Dent. Res. 76(2): 665 – 672, 1977