Amorphous reprecipitated chitosan as a novel morphological form

In order to overcome the intractable nature of chitosan, which has delayed the basic and utilization research of this biopolymer having remarkable biological activities, destruction of the crystalline structure was studied. Chitosan was dissolved in aqueous acid, reprecipitated in alkali, and freeze-dried under appropriate conditions to prepare a fluffy cotton-like material, which was amorphous and had almost the same molecular weight as the original chitosan. It exhibited highly improved chemical reactivity as confirmed by the acetylation and enhanced adsorption capability toward copper ion. Full N-acetylation of the reprecipitated chitosan afforded structurally uniform chitin, which was also found to be amorphous. These results indicate the high potential of this new morphological form of chitosan possibly leading to a wide range of utilizations of this under-utilized biological resource.