The Preparation And Characterization Of Chitosan With Low Molecular Weight And Its Inhibitory Activity To Aspergillus Flavus

Low molecular weight water-soluble chitosan has been used in food, medicine, pesticide industry widely due to the antifungal activity. But the fast and efficient system preparation method of low molecular weight water soluble chitosan need further research, and the antifungal activity of chitosan with low molecular weight to Aspergillus flavus has not been reported.In this paper, the orthogonal experiment method was used to optimize the parameter of preparation of low molecular weight chitosan by hydrogen peroxide oxidation degradation combined with microwave and ultrasonic radiation degradation. The structure of low molecular weight chitosan was characterized by infrared spectroscopy and differential thermal analysis. the molecular weight and degree of deacetylation were mensurated. At last, the inhibitory activity of low molecular weight water-soluble chitosan on Aspergillus flavus was analysised by using the inhibitory concentration gradient method, inhibition zone method and micromorphology analysis. The main results were summarized as follows:1. The orthogonal experiment showed that the optimization parameters of preparation of low molecular weight chitosan were summarized as follows:the concentration of H2O2 was 8%, and the reaction time was 10 minutes combined with microwave and ultrasonic radiation degradation 3 minutes. The average molecular weight of product was 4795.6Da.2. Infrared spectrum analysis showed that degradation of chitosan was caused by the bond cleavage of (1→4) glycosidic; The degree of deacetylation increased in the course of degradation. The differential thermal analysis showed that thermal stability of low molecular weight water-soluble chitosan was lower than that of raw materials chitosan.3. The product of low molecular weight chitosan has the inhibitory effect on Aspergillus flavus, There was a positive correlation between inhibitory effect and concentration. Micromorphology analysis showed that the hyphae and spores were inhibited after treatment by the low molecular weight chitosan.