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Preparations Of Chitosan Organic Acid Salts And Researches On Their Antibacterial Activities

Posted on:2008-11-09Degree:MasterType:Thesis
Country:ChinaCandidate:Y LiFull Text:PDF
GTID:2120360242455773Subject:Marine biology
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Chitin is a natural polysaccharide which is usually obtained from shells of crustaceans such as crab, shrimp, and crawfish. Chitosan is a partially N-deacetylated derivative of chitin, and consists of polymeric (1→4)-linked 2-amino-2-deoxy-β-D-glucopyranose units. Due to the unique polycationic nature, chitosan and its derivatives have been proposed for various applications in biomedical, food, agricultural, biotechnological and pharmaceutical products. Chitosan has a broad spectrum of antimicrobial activities, high bactericidal rates and low toxicity toward mammalian cells, making it a potential biocide in food preserving. However, the poor solubility of chitosan at neutral and higher pH limits its applications. Some modification has been attempted. But the traditional method of modifying is to introduce some covalent bond, which is usually complex and sometimes changes some of the properties of chitosan.In this paper, a new approach to prepare solid chitosan organic salts is reported. Chitosan (Mw=82kDa, DD=88.7%) was prepared first. Chitosan and organic acid was simply reacted and the chitosan organic salts (COS) were prepared: chitosan formait (CF), chiotsan acetate (CA), chitosan propionate (CP), chitosan lactate (CL). It was demonstrated by the titration curves that there was only one inflexion point, compared with two inflexion points in chitosan. It could be inferred from the FTIR that chitosan is linked by electrovalent bond other than covalent bond with the acid, so the products still keep the structure and antibacterial activity of chitosan and can be prepared easily. The solubility, titration curve, stability, IR spectrum and other basic characterizations of the products are evaluated. It is demonstrated that the chitosan organic salts are water soluble and stable in common conditions.The antibacterial activities against E. coli (gram negative), S. aureus (gram positive) and C. guilliermondii have been investigated by MTT method. It was found that chitosan organic salts have good antibacterial acitivities. Take CA and E.coli for example, the growth of E. coli was regular at the concentration of 0.05% (w/v); when the concentration of CA reached 0.08%(w/v), the bacteria grew more than the ones with no CA; CA would inhibit the growth of E.coli at the concentration of 0.13% (w/v). It could also inhibit the growth of S.aureus at the concentration of 0.20% (w/v), and C. guilliermondii at 15ppm (w/v). It also demonstrated that COS showed stronger antibacterial activities with the increase of concentration of COS. Different kinds of microbiology also cause different antibacterial activities. The organic acid nearly has no influence on the activities. And the concentration of the bacterium suspension during incubation has effect on the MIC of COS.The possibility of the product being used as a new kind of preservative in foods was also investigated in this paper. It is conferred that the chitosan organic acid salts will be a kind of cheap, convenient, and effective preservative in foods.
Keywords/Search Tags:chitosan, chitosan organic salt, water soluble chitosan, antibacterial acitivity, preservative
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