The Study Of Chitosan Degradation And Its Inhibition Activity On Pathogen Of Eucalyptus Bacterial Wilt

China possesses rich resources of chitosan. Because of its special biological activity, itis a Potential biological resource with great development. Therefore, it is verySignificance to explore its new activity. In this study, the polymer chitosan was used asraw material, several small molecular weight chitosan were prepared by the method ofH2O2oxidation and the effect of different experimental parameters on molecular size ofthe degradation product were also explored. Besides the works above, the anti-bacterialactivity of degradation product above on four different strains were further studied.Finally, the anti-bacterial kinetics and the morphology of bacterial treated by differentmolecular weight chitosan were researched. The works above lay the foundation oncommercial application of chitosan. The results were as follows：(1) the macromolecules chitosan was degraded using the method of H2O2-HAC system,and the degree of deacetylation and its intrinsic viscosity of degradation product weredetermined. The effects of concentration of hydrogen peroxide (C), temperature (T) andtime (t) on the size of chitosan were studied. The effect of three factors above on chitosandegree of deacetylation (DD), intrinsic viscosity (η) were also analyzed. At last, theoptimum degradation conditions were obtained using orthogonal experiment. The resultsshow that: the biggest affection of various factors on the DD is: T> t> C, onηsignificancelevel is: T> C> t and on the molecular weight (M) is: T> C> t. The optimum conditionsfor the degradation conditions were as following: the degradation time is50min, thedegradation temperature is60℃and concentration of hydrogen peroxide is12%.(2) The anti-bacterial effect of the degradation products with different molecularweight on76-eggplant Ralstonia Lal coli, RS-Wilt Pathogen,302-Paenibacillus polymyxa and199-Bacillus cereus rejection were explored; the anti-bacterial effect ofdifferent molecular weight chitosan in different PH value were also studied; based on theworks above, the minimum inhibitory concentration (MIC) was determined. The resultsshowed that: five kinds chitosan with different molecular weight can inhibit the growth offour bacteria above; the anti-bacterial effect was improved when the molecular weight ofchitosan become smaller and the concentration of chitosan become greater. The chitosanwith molecular weight of2200and50000have the best anti-bacterial effect on76-eggplant Ralstonia Lal coli and RS-coli bacteria Wilt, the anti-bacterial effect of the twochitosan above on302-Paenibacillus polymyxa and199-Bacillus cereus rejection wassignificantly weakened. The best anti-bacterial effect was obtained as PH5.0to6.5, andthe anti-bacterial rate was almost100%.(3) The inhibitory mechanism of chitosan with molecular weight of2200and50000was explored by the anti-bacterial kinetics and the morphology of bacterial treated bydifferent molecular weight chitosan. The results showed that: the morphology of76-formeggplant Ralstonia Lal and RS-coli pathogens Wilt were changed significantly: fromcircular to rod. The morphology of302-Paenibacillus polymyxa was changed from rodinto circle treated by the chitosan with molecular weight of2200.