ENHANCEMENT OF ANTIMICROBIAL ACTIVITY OF CHITOSAN BY IRRADIATION

Antimicrobial activity of irradiated chitosan was studied against Esch erichia coli B/r. Irradiation of chitosan at 100 kGy under dry conditi ons was effective in increasing the activity, and inhibited the growth of E coli completely. The molecular weight of chitosan significantly decreased with the increase in irradiation dose, whereas the relative surface charge of chitosan was decreased only 3% by 100 kGy irradiatio n. Antimicrobial activity assay of chitosan fractionated according to molecular weight showed that 1 x 10(5)-3 x 10(5) fraction was most eff ective in suppressing the growth of E coli. This fraction comprised on ly 8% of the 100 kGy irradiated chitosan. On the other hand, chitosan whose molecular weight was less than 1 x 10(5) had no activity. The re sults show that low dose irradiation, specifically 100 kGy, of chitosa n gives enough degradation to increase its antimicrobial activity as a result of a change in molecular weight.