Physicochemical and biological properties of chitosan derivatives with varying molecular weight produced by chemical depolymerization

Chitosan derivatives with lower Mw were prepared by chemical depolymerization using hydrochloric acid. This modification improves functional and biological properties of shrimp chitosan and facilitates its utilizations. The obtained chitosan depolymerization products (CDP) were characterized in terms of molecular weight (Mw), degrees of acetylation (DA) and polymerization (DP), solubility, viscosity, crystallinity, and FTIR spectroscopy. High Mw-CDP (from 94.10 to 396.46 kDa) and low Mw-CDP (<4.4 kDa), with a DP up to 7, were withdrawn at different hydrolysis times. It is clearly demonstrated that the viscosity, the DA, and the crystallinity decreased upon depolymerization, especially in low Mw-CDP, while solubility in water and acetic acid was 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.