Antimicrobial activity of chitosan N-betainates

The effect of degree of substitution on the antimicrobial activity of water-soluble quaternary chitosan N-betainates was determined against Escherichia coli and Staphylococcus aureus. Chitosan N-betainates showed low antimicrobial activity in neutral conditions and the glucosamine N-betainate prepared as a reference compound showed low activity also in acidic conditions. However, the antimicrobial activity increased with decreasing degrees of substitution in acidic conditions (pH 5.5), which suggests that for efficient antimicrobial action, the positive charge should be situated in the amino group of chitosan, rather than in the quaternary substituent.