Molecular weight dependent antimicrobial activity by chitosan

Chitosan oligomers of average molecular weight 9300(P9300) and 2200(P2200) were prepared by nitrous acid degradation followed by the reduction of 2,5-anhydromannose terminal by sodium borohydrate. Although P9300 provided the growth inhibition of Escherichia coli, P2200 was not growth inhibitor but growth accelerator. The stacking of P9300 to cell wall of E. coli was confirmed by the use of FITC(fluorescein isothiocyanate) labeled chitosan oligomer using the Confocal Laser Scanning Microscope. The permeation of P2200 was also observed through cell wall without stacking to cell wall. The effective growth inhibition of bacteria was assumed to be the prevention of delivery of nutrition through cell wall.