Radiation depolymerization of chitosan to prepare oligomers

Radiation depolymerization of chitosan was carried out by gamma irradiation in the solid state. The radiation-chemical depolymerization yield of chitosan in the solid state, Gd, determined by gel permeation chromatography, is 0.9 for chitosan 10B and 1.8 for chitosan 8B. Low molecular weight chitosan/or oligochitosans were separated from a chitosan depolymerized by gamma radiation, using mixtures of methanol-water and acetone as the solvents. Due to the differences in solubility revealed upon raaiolysis, extracts became subdivided into precipitates and soluble fractions. The biological effect of oligochitosan in each fraction was evaluated; the preliminary results indicated that the oligochitosan with (M) over bar (w) = 2 x 10(4) inhibited the growth of fungi at 100 ppm and that with (M) over bar (w) = 800 only enhanced the growth of the same typical fungi. (C) 2003 Elsevier B.V. All rights reserved.