Chitosan Depolymerization: A Simple and Promising Chemical Process for the Preparation of Bioactive Varying Molecular Weight Derivatives

Abstract In order to improve functional and biological properties of shrimp chitosan and to facilitate its utilization, chitosan derivatives were prepared by chemical depolymerization using hydrochloric acid (6 M) during 2 h. The obtained chitosan depolymerization products (CDP) were characterized in terms of molecular weight (Mw), acetylation (AD) and polymerization (DP) degrees, solubility, viscosity and crystallinity, and analyzed by FTIR spectroscopy. High Mw-CDP varying from 396 to 94 kDa and low Mw-CDP (< 4.4 kDa), with a DP up to 6 determined by MALDI-TOF, were withdrawn at different hydrolysis time and then desalted on chromatography Sephadex G-25 column. It is clearly demonstrated that the viscosity, the AD and the crystallinity decreased upon depolymerization, especially in low Mw-CDP. While, solubility in water and acetic acid were highly improved. FTIR analysis showed similar spectra of chitosan and CDP. The antibacterial, antifungal and antioxidant properties of CDP were investigated and demonstrated that they were related to its Mw. Indeed, as compared to chitosan, high Mw derivatives, especially C120, possess higher antibacterial and antifungal potentials. While, low Mw-CDP, especially H120, exhibited the highest antioxidant properties. Interestingly, the used chemical depolymerization process seems to be an efficient, simple and easy method to produce bioactive chitosan derivatives with attractive characteristics to be applied in an industrial scale, especially as functional-food components.