The effect of the molecular weight of chitosan on antimicrobial activity wa
s investigated using three chitosans of different molecular weights [1800 (
water soluble), 100,000, and 210,000] and similar degrees of deacetylation
(86-89%). Cotton fabrics were treated with chitosan by the pad-dry-cure met
hod. The molecular weight dependence of the antimicrobial activity of chito
san was more pronounced at a low treatment concentration. Chitosans with mo
lecular weight of 100,000 and 210,000 effectively inhibited Staphylococcus
aureus at a 0.5% treatment concentration. Chitosan with a molecular weight
of 1800 was effective against S. aureus at a 1.0% treatment concentration.
Escherichia coli was effectively inhibited by chitosan with a molecular wei
ght of 210,000 at a 0.3% treatment concentration and by chitosans with a mo
lecular weight of 1800 and 100,000 at a 1.0% treatment concentration. Prote
us vulgaris was effectively inhibited by chitosans with molecular weight of
100,000 and 210,000 at a 0.3% treatment concentration and by chitosan with
a molecular weight of 1800 at a 0.5% treatment concentration. None of the
chitosans significantly inhibited Klebsiella pneumoniae and Pseudomonas aer
uginosa below a 1.0% treatment concentration. Chitosans with high molecular
weights were more effective in inhibiting bacterial growth than chitosans
with low molecular weights. (C) 2001 John Wiley & Sons, Inc.