Papain And Hydrogen Peroxide Preparation Of Low Molecular Weight Chitosan

Chitosan is an environmental friendly crude macromolecule material. It is made from Chitin by deacylation that is distributed widely in nature. Chitooligosaccharide that is the degradation product of chitosan has many excellent capabilities. Biocompatible and biodegradable, Moisture retention, Anti-tumor activity, Strengthening the immune system, are used as drugs and absorbent agent. It has received much attention in many fields due to the distinct pHysiologic activities and potential functions. But the application of chitosan was limited duo to its low wate-solubility. Therefore how to prepare the low molecular weight chitosan,effectively through a series of physical and chemical methods caused increasingly concerned. At present, the preparation methods of low molecular weight chitosan mainly include chemical degradation, enzyme degradation and pHysical degradation, and so on. This paper studied the process of chitosan degradation with hydrogen peroxide oxidation, papain enzymatic and papain combined with hydrogen peroxide, respectively. Through experiment, we derive the optimum technological conditions of the three various methods and test the characterization of low molecular weight chitosan.(1) The process and the mechanism of chitosan degradation with hydrogen peroxide was sutdied, and the effect of temperature, amount of hydrogen peroxide, time, were investigated. The structure of degradated products were characterized by FT-IR, TG-DTA, and water-soluble test. Results showed that the optimal conditions for preparation of low molecular weight chitosan were as follows:reaction temperature68℃, reaction time5h, hydrogen peroxide (H2O2/sugar dosage units=1.5),2%of acetic acid medium. Through the viscosity test,we know that hydrogen peroxide degradated chitosan effectively, and low weight molecular chitosan was obtained. The structure of degradated products were characterized by FT-IR, TG-DTA, and water-soluble test. The results show that the structure of chitosan which is degradated have not changed, with reducing of molecular weight, water-soluble was enhanced.(2) The depolymerization of chitosan by papain was studied. By determining the concentration of reducing sugar and viscosity in chitosan solution, the effects on the efficiency of catalytic degradation of chitosan by papain were investigated. Results show that the optimum reaction conditions is:reaction temperature45℃, pH value4.2, papain dosage (papain:substrate than=1.5), chitosan solution concentration0.5%, reaction time24h. Through the viscosity determination, we know that after degradating the molecular weight of oligochitosan is about1×104, water-soluble was improved.(3)The papain-H2O2degradation of chitosan was performed in this paper. The effects of temperature, pH value, the adding time of hydrogen peroxide, reaction time on the molecular weight of chitosan were analyzed in detail, and the structure of products which were degraded by chitosan were characterized by FT-IR. The results showed that the optical pH value for degradation was4; the temperature of papain was45℃; the temperature of hydrogen peroxide was60℃; the reaction time was24h. Through the experiment, we could gain the conclusion that the decrease of molecular weight could lead to the change of lattice structure, but the chemical structure was the same as native chitosan.