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 to prepare antibacterial oligochitosans. in this study, the effect of solvent on the 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 solution at dose range of 2-200 kgy. the changes of molecular weight with irradiation dose which were monitored by viscometric measurements showed that the solvent led to the reduction of degradation dose. therefore, the molecular weight of solid chitosan was reduced from 400,000 to 48,000 after irradiation at 50 kgy, whereas the molecular weight of aqueous solution of chitosan reached 32,000 after irradiation at10 kgy. antibacterial investigations showed that growth of pc in aqueous solution of chitosan irradiated at 10 kgy is equal to the growth of pc in solid chitosan irradiated at 50 kgy. ftir spectra of the irradiated samples showed that the radiation degradation of chitosan in solid and aqueous solution must have occurred through the breakage of glycosidic bonds. the variations of glycosidic bond were in consistent with the viscometric results based on the effect of solvent on the reduction of degradation dose of chitosan