The Role of Solvent on Radiation Degradation and Antibacterial Activity of Chitosan Against Pectobacterium Carotovorum

Radiation degradation of chitosan is one of the most important methods toprepare antibacterial oligochitosans. In this study, the effect of solvent onthe reduction of degradation dose and enhancement of the antibacterialactivity of chitosan against Pectobacterium Carotovorum (PC) has been considered.Gamma radiation degradation was applied to chitosan as solid and aqueous solutionat dose range of 2-200 kGy. The changes of molecular weight with irradiation dosewhich were monitored by viscometric measurements showed that the solvent led tothe reduction of degradation dose. Therefore, the molecular weight of solid chitosanwas reduced from 400,000 to 48,000 after irradiation at 50 kGy, whereas the molecularweight of aqueous solution of chitosan reached 32,000 after irradiation at10 kGy. Antibacterial investigations showed that growth of PC in aqueous solutionof chitosan irradiated at 10 kGy is equal to the growth of PC in solid chitosan irradiatedat 50 kGy. FTIR spectra of the irradiated samples showed that the radiationdegradation of chitosan in solid and aqueous solution must have occurred through thebreakage of glycosidic bonds.