Oxidative Degradation of Chitosan to the Low Molecular Water-Soluble Chitosan over Peroxotungstate as Chemical Scissors

Abstract

Low molecular water-soluble chitosan was prepared by the depolymerization of chitosan in the presence of a series of catalysts with active W(O2) sites. Both the peroxo species [W2O3(O2)4]2- and {PO4[WO(O2)2]4}3- showed high efficiency in the degradation of chitosan, indicating that the degradation mechanism did not follow the radical mechanism. That means •OH is not the active species, which has been proven by the fluorescence spectra. H2O2 acted as an oxidant to regenerate the active W(O2) sites in the depolymerization of chitosan. The developed catalyst (TBA)3{PO4[WO(O2)2]4} is recoverable.

Optimization and Characterization of Chitosan Enzymolysis by Pepsin

“…These results demonstrated that the structures of the main chain of the initial chitosan and LMWCs were the same. The NH 2 amino groups had a characteristic peak near 3462 cm −1 , which was overlapping by the peak due to the –OH group [ 23 ]. The occurrence of absorption peaks at around 2900 cm −1 was assigned to the asymmetric stretching vibration of the –CH 2 –, and the rapid reduction in the intensity for the LMWCs was probably attributed to degradation of chitosan after hydrolysis.…”

“…A new absorption peak not appearing in the initial chitosan sample was observed at around 344 cm −1 , which suggested the existence of a chemical reaction in the LMWCs. The peak could be assigned to the n→π* transition for the carboxyl group in the LMWCs formed after the main chain scission of chitosan [ 23 ]. The result of FTIR analysis further confirmed that carbon-oxygen double bonds formed after the degradation of chitosan occurred by the ring opening, turning chitosan into one with low molecular weight.…”

Stability of Chitosan—A Challenge for Pharmaceutical and Biomedical Applications

“…Chitosan is degraded in vivo by several enzymes, mainly by lysozyme—a non-specific protease present in all mammalian tissues—producing non-toxic oligosaccharides which can be then excreted or incorporated to glycosoaminoglycans and glycoproteins [ 30 ]. In vitro degradations of chitosan via oxidation, chemical, or enzymatic hydrolysis reactions are commonly used methods for the preparation of low molecular chitosan under controlled conditions [ 31 ]. The molecular weight, polydispersity, deacetylation degree, purity level and moisture content play a crucial role in determining the mechanism and the speed of polymer degradation.…”

Effect of shrimp shells milling on the molar mass of chitosan

“…-Chitosan: oxidative degradation by catalysts with peroxide active sites (for example, W (O 2 )) leading to a depolymerization rate higher than 90% [2] ; depolymerization by a plasma treatment solution applied to the metal-chitosan complex allowed to obtain oligomers (in order of 10 3 Da); however, the technical…”