Molecular weight effect on antimicrobial activity of chitosan treated cotton fabrics

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.