Water-solubility of chitosan and its antimicrobial activity
2006
Qin, C. | Li, H. | Xiao, Q. | Liu, Y. | Zhu, J. | Du, Y.
Chitosan samples with different molecular weights were prepared by depolymerization with hemicellusase, and water-soluble half N-acetylated chitosan samples were obtained by N-acetylation with acetic anhydride. The action of chitosans with molecular weights Mw from 1.4x10³ to 4.0x10⁵ on the growth of Staphylococcus aureus, Escherichia coli and Candida albicans was explored by microcalorimetry. The water-soluble half N-acetylated chitosans and chitooligomers had no significant antimicrobial activity. Moreover, water-soluble chitosans and chitooligomers promoted the growth of C. albicans. In contrast, water-insoluble chitosan in acidic medium exhibited inhibitory effect against these microorganisms. The water-insoluble chitosans with Mw around 5x10⁴ were the optimum for antimicrobial action in these tested samples. The antimicrobial mechanism of dissolved water-insoluble chitosan was hypothesized as forming an impervious layer around the cell. The results suggest that optimum chitosan as food preservative should be water-insoluble chitosan from mild depolymerization of native chitosan.
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