Antimicrobial Activity of Chitosans Degraded by Different Methods

• 1、National Engineering Laboratory for Clean Technology of Leather Manufacture, Sichuan University, Chengdu 610065, China

Abstract：Antimicrobial activities of chitosans degraded by different methods (hydrogen peroxide/pepsin degradation) were examined against Escherichia coli (E. coli, gram-negative bacterium), Staphylococcus aureus (S. aureus, gram-positive bacterium) and Candida albicans (C. albicans, yeast). The results indicated that the antimicrobial activity of chitosan is determined by the degradation method, molecular weight (Mw) and concentration of chitosan, and the characteristic of the microorganism tested. All chitosans exhibit high inhibitory rates (≥99.78%) against three tested microbes at a concentration of ≥0.5 g/L. Antimicrobial activities of chitosan against E. coli and C. albicans are greatly depended on the concentration of the sample when the value of it is in the range of 0.25～0.125 g/L. Chitosan shows high inhibitory rate against bacteria at either high or low Mw when the mass average Mw of it is in the range of 1460～285 kDa, which indicating that Mw might have dual effects on its antibacterial activity. The antifungal activity of chitosan might have greater concerned to the activation of defense processes. Degradation method has great influence on the antimicrobial activity, especially antifungal activity, of chitosan by changing the Mw and acetyl groups’ distribution of the polymer, which might be one of the reasons that why there are inconsistent conclusions obtained concerning the antimicrobial activity of chitosan.

Keywords： chitosan antimicrobial activity hydrogen peroxide pepsin degradation