Deacetylation of chitin hydrogel by using solution plasma

Abstract

Deacetylation is a chemical reaction used for converting chitin into chitosan. Since native chitin has low reactivity to the deacetylation reaction, chitin hydrogel, an amorphous form of chitin, was applied in this study. Chitin hydrogel was prepared by dissolving native chitin in a calcium chloride-saturated methanol solution and subsequently precipitaing in a large amount of water. Solution plasma was introduced to the deacetylation reaction of chitin in order to reduce the NaOH concentration required in the reaction. In the solution plasma system, several highly active species such as hydroxyl radicals, hydroperoxyl radicals, and free electrons were generated. These highly active species might help to facilitate the deacetylation reaction of chitin, which resulted in using a lower concentration of NaOH solution. The deacetylation reaction of chitin hydrogel was carried out by varying concentrations of NaOH in alcohol solutions to 1%, 5%, 10%, and 12%, By using solution plasma, the degree of deacetylation of the chitin hydrogel increased with increasing NaOH concentration as well as the plasma treatment time. The chemical structure and degree of deacetylation of the products were determined by FTIR and NMR. The molecular weight and molecular weight distribution of the obtained chitosan were investigated by GPC. Moreover, the antimicrobial activity of chitosan obtained from solution plasma method was also evaluated against E. coli and S. aureus.