Mechanism of Bacteriostatic Effect of Chitosan

• Main Authors: Yu-Sheng Chu, 朱祐生
• Other Authors: Ching-Hua Su Ph.D.
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/41463425887041382845

碩士 === 臺北醫學大學 === 生物醫學材料研究所 === 92 === Abstract The exact mechanism of the antimicrobial action of chitin, chitosan is still unknow. However, according to our previous studies , chitosan can not completely inhibit the growth of bacterial on medium in nutrient agar or nutrient broth. So the hypothesis proposed that bacteria was unable to obtain amino acids through hydrolyzing protein in presence of chitin and chitosan and the growth would be rendered if small molecule nitrogen sourced were deprived. The binding ability of chitin and chitosan to proteases produced by gram-negative and gram-positive bacteria that resulted in growth inhibition of bacteria with protein was used as a sole nitrogen source. Gelatin medium was used to detect gelatinase production of bacteria and it was found that E. coli , Pseudomonas aureginosa and Bacillus subtilis, Staphylococcus aureus were positive in the test. Based on this mechanism spectrophotometry with a 96 well plate were developed to detect the antimicrobial activity of chitin and chitosan. Zymographic gel analysis indicated that proteases from E.coli, P. aureginosa , B. subtilis, S. sureus were inhibited by chitosan with a dose response reaction. The result confirmed that chitosan inhibited protease activity and it is a distinct the mechanism of the antimicrobial action of chitosan . Annexin Ⅴ-PI flow cytometry analysis on the bacteria indicated that chitosan or chitin caused asymmetric charge of bacteria plasma membrane to 90 % in E.coli,and 30% in P. aureginosa with a death ratio of 28 %and 10 % ,respectively. However, only slightly change was observe in B. subtilis 22 % and S. sureus 6 % . This information also in good agreement to the hypoesis that chitin or chitosan might effected more on G(-) that on G(+) bacteria , due to the binding of LPS in the outer membrane of G(-) bacteria.