A Study on the Correlation between Structural Characteristics and Biological Activity of Water-soluble Chitosan

Abstract

The kinetic properties of chitosanase according to chemical and structural modifications of chitosan were evaluated by relative enzyme activity and bioactivity of hydrolysates. Changes in the specificity of the chitosanase for the substrate showed a significant difference under the optimal reaction conditions. The increase of reducing sugar content according to the activity of the chitosanase was significantly observed against carboxymethyl-chitosan (CM-CTSN) compared to glycol chitosan (GL-CTSN) and water-soluble chitosan (WSC) used as a control. Each chitooligosaccharide designated to COS, CM-COS, and GL-COS showed similar results in various antioxidant activity evaluations so that no significant difference could be confirmed. Significant antibacterial activities of three types of water-soluble chitosan derived COS, CM-COS, and GL-COS against Escherichia coli and methicillin-resistant Staphylococcus aureus (MRSA) were not confirmed. However, both ferric reducing antioxidant power (FRAP) and 2,2’-azino-bis (3-ethylbenzothiazoline 6-sulfonic acid) diammonium salt (ABTS) radical scavenging ability confirmed their significant antioxidant activity, but it was evaluated as irrelevant to the difference in molecular weight. Although there is a clear difference in the substrate specificity of the enzyme depending on the chemical structural modification of chitosan, our results suggest that the biological activity of COS was not significantly affected regardless of the presence or absence of a water-soluble functional group. Therefore, based on the results of this study, we suggest the need for follow-up studies to investigate the correlation between the water solubility of chitosan, enzymatic activity, and biological activity.