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Study on the Degradation, Inhibition Activity and Application of Chitosan

Author: FengXiaoQiang
Tutor: SuZhongXing;YangSheng
School: Lanzhou University
Course: Physical and chemical
Keywords: Chitosan Degradated products Inhibition Application
CLC: O636.1
Type: Master's thesis
Year: 2007
Downloads: 1206
Quote: 3
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Abstract


Based on the antibacterial activity of chitosan , the inhibition abilities and application of chitosan and its derivatives were investigated in this dissertation.The study will extend the future of chitosan in the applicational fields of antibacterial material, food industry and medicine.The study contents and results were listed as follows.1. A series of chitosan with different molecular weight were prepared taking advantage of degradation of chitosan under the homogeneous phase of H2O2-HAc.The structure of degradated products were characterized by FT-IR, TG-DTA, XRD and SEM. In addition, the effect factors on degradation such us temperature, reaction time, the concentration of H2O2 and acetic acid,etc were discussed. The optimal conditions for preparation of low molecular weight chitosan were as follows: temperature（60℃-70℃）, reaction time 6 h, the concentration of H2O2 and acetic acid is 3%-10% and 1 %-5 % ,respectively.Furthermore,it was confirmed that the degradation of chitosan in acetic acid medium was a oxidation-coordinate hydrolytic reaction in virtual.2. In vitro the antibacterial activity of Chitosan, Chitooligosaccharides and Water-soluble chitosan with different molecular weight to some kinds of bacteria were studied,and the relationship between antibacterial activity and molecular weight,concentration of chitosan were studied. The results showed that all of the tested chitosan and its derivatives have better inhibition activity to bacteria, while poor or good antibacterial activity was ascribed to different strains. Generally speaking, the antibacterial activity against Gram positive （G+）was prior to Gram negative（G-）.Compared with ehitoligosaccharides and Water-soluble chitosan, chitosan had the stronger antibacterial activity, moreover, the inhibition activity increased by the increasing of concentration. However, Water-soluble chitosan have not this kind of relationship between antibacterial activity and concentration, which have best antibacterial activity only in a proper low concentration. Chitosan and its derivatives had better antibacterial activity in acid medium.3. In vitro the antibacterial activity of chitosan was evaluated against Asperillus niger, Saccharomyces cerevisiae Hansen and Candida albicans, the relationship between antibacterial activity and molecular weight, concentration were studied. Especially the antibacterial activity towards Asperillus niger was studied, also the antibacterial mechanism was discussed according to ultrastructure by TEM. The results indicated that antibacterial activity against Saccharomyces cerevisiae Hansen and Candida albicans improved by the increasement of chitosan concentration. However,as for Asperillus niger, the tested chitosan with minimal molecular weigh（50 kDa） and minimal concentration（0.2 %） possessed strongest antibacterial activity,and could absolutely inhibit the growth of Asperillus niger.It was found that chitosan with higher molecular weigh and concentration had the function to accelerate the growth of Asperillus niger,which enlightened us to exploit a higher active chitosanase using it.4. In this chapter, the effect of amino groups, the degree of deactylation of chitosan（DD.）, PH and metal ions on antibacterial activity were investigated firstly.Then the ultrastructures of bacteria before and after interacted with chitosan were observed by TEM. It was obvously discovered that different mechanism of inhibition activity of chitosan were resulted by different molecular weight. The above conclusion was further proved by biochemical analysis instrumentation.It was found that the content of LDH and r-GT enzyme contained in the bacteria supematants that have interacted with chitosan were higher than control signicantly,which indicated that something in bacteria had outflowed.It was clear that inhibition activity of chitosan mainly by destroying the outer structure and function of bacteria.5. As a new natural antimicrobial agent, the possible uses of chitosan as a food preservative on acidish drink were studied in this chapter, and the range of molecular weight which possessing the best preservation ability was obtained. The hygroscopicity, moisture retention and inhibition activities to three bacterial of water-soluble and chitooligosacsharides were studied in this chapter, which would accelerate the application of chitosan in cosmetic and food industry.

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CLC: > Mathematical sciences and chemical > Chemistry > Polymer chemistry ( polymer ) > Natural polymers ( polymer ) > Polymer polysaccharides
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