Effect of deacetylation of chitosan on physicochemical properties, antioxidant and antibacterial activities of chitosan-mannose derivatives.

Abstract

This paper investigates the physical, chemical, and antibacterial properties of water-soluble chitosan derivatives. Preparation of the water-soluble chitosan derivatives was done by the Maillard reaction (MR) between chitosan (the degree of deacetylation (DD) being 50%, 70%, and 90%) and mannose. No organic reagent was used in the process. Systematic evaluations of the effects of chitosan DD on the reaction extent, the structure, the composition, as well as the physicochemical properties, antioxidant properties, and bacterial inhibitory properties of the finished chitosan-mannose Maillard reaction products (Mc-mrps) were carried out. Based on the experimental data obtained from the Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), Pyrolysis-gas chromatography-mass analysis (PY-GC-MS), and 1H-NMR, the Mc-mrps formed from chitosan with different DDs had different structures and components. An increase in the DD of chitosan led to a significant increase in the degree of reaction, color difference (△E), and solubility (p<0.05). The zeta potential and particle size of the Mc-mrps were also influenced by the DD of chitosan. Additionally, the antimicrobial action against Gram-positive (S.aureus and Bacillus subtilis) and Gram-negative bacteria (E.coli and Salmonella typhimurium) as well as antioxidant activity were enhanced by the incorporation of mannose. This was also achieved by the increase of the DD of chitosan. The results of the study suggest that chitosan was derived with mannose to yield a novel, water-soluble polysaccharide with better antioxidant and antimicrobial activities. The DD of chitosan had a significant effect on the properties of the Mc-mrp, which can serve as a reference point for the subsequent preparation and application of such derivatives. This article is protected by copyright. All rights reserved.