Depolymerization of Chitin and Chitosan under Hydrothermal Conditions.

Abstract

For the utilization of chitinous materials in various fields, depolymerization has been one of the important subjects. Chitin and chitosan are easily hydrolyzed with concentrated hydrochloric acid or hydrolase (chitinase, chitosanase, lysozyme), and decomposed with hydrogen peroxide and so on. Therefore, transformation of chitin and chitosan into their low molecular weight homologs usually needs some catalysts or reagents. Recently, it has been proposed that cellulosic materials are decomposed in super critical water or subcritical water. But it is too difficult to control the reaction conditions for decomposition of chitin and chitosan in supercritical water and subcritical water. Furthermore the experimental device is very expensive.In this study, the decomposition of amorphous chitin, deacetylated chitin (partially deacetylated chitin prepared under the homogeneous conditions) and amorphous chitosan was performed under the hydrothermal conditions (120-180 degrees centigrade) without any catalysts. The degradability of amorphous chitin and amorphous chitosan were compared with that of powdered chitin and chitosan which have rigid crystal structure. As the results, amorphous chitin and amorphous chitosan were decomposed under the hydrothermal conditions at 120-180 degrees Centigrade. But powdered chitin and chitosan were not almost decomposed under these conditions.