Relationship between antibacterial activity of chitosan and surface characteristics of cell wall.

KEY WORDS anti-bacterial agents; chitosan; cell wall ABSTRACT AIM: Five representative waterborne pathogens were used to illustrate the relationship between chitosan's antibacterial activity and the surface characteristics of the bacterial cell wall. METHODS: Chitosan was prepared with averaged 75 % or 95 % deacetylated degree to examine its antibacterial activity against waterborne pathogens. Fresh microbial inoculants for the antibacterial assessment were prepared on nutrient agar at 37 ºC for 24 h. The evaluation items of antibacterial mechanism included hydrophilicity and negative charge analysis of cell surface, and adsorptive characteristics of chitosan to bacterial cell. All the experiments were applied in triplicate tests at least. RESULTS: Although cell wall hydrophilicity was similar among Gram-negative bacteria, the distribution of negative charge on their cell surfaces was quite different. More negatively charged cell surfaces had a greater interaction with chitosan, a phenomenon further confirmed by transmission electron micrography (TEM). CONCLUSION: Results showed the hydrophilicity in Gram-negative bacteria was much higher than in Gram-positive ones. The correlation coefficient 0.988 between the amount of absorbed chitosan and its inhibition efficiency indicated a close relationship

Determining the degradation efficiency and mechanisms of ethyl violet using HPLC-PDA-ESI-MS and GC-MS

<p>Abstract</p> <p>Background</p> <p>The discharge of wastewater that contains high concentrations of reactive dyes is a well-known problem associated with dyestuff activities. In recent years, semiconductor photocatalysis has become more and more attractive and important since it has a great potential to contribute to such environmental problems. One of the most important aspects of environmental photocatalysis is in the selection of semiconductor materials like ZnO and TiO₂, which are close to being two of the ideal photocatalysts in several respects. For example, they are relatively inexpensive, and they provide photo-generated holes with high oxidizing power due to their wide band gap energy. In this work, nanostructural ZnO film on the Zn foil of the Alkaline-Manganese Dioxide-Zinc Cell was fabricated to degrade EV dye. The major innovation of this paper is to obtain the degradation mechanism of ethyl violet dyes resulting from the HPLC-PDA-ESI-MS analyses.</p> <p>Results</p> <p>The fabrication of ZnO nanostructures on zinc foils with a simple solution-based corrosion strategy and the synthesis, characterization, application, and implication of Zn would be reported in this study. Other objectives of this research are to identify the reaction intermediates and to understand the detailed degradation mechanism of EV dye, as model compound of triphenylmethane dye, with active Zn metal, by HPLC-ESI-MS and GC-MS.</p> <p>Conclusions</p> <p>ZnO nanostructure/Zn-foils had an excellent potential for future applications on the photocatalytic degradation of the organic dye in the environmental remediation. The intermediates of the degradation process were separated and characterized by the HPLC-PDA-ESI-MS and GC-MS, and twenty-six intermediates were characterized in this study. Based on the variation of the amount of intermediates, possible degradation pathways for the decolorization of dyes are also proposed and discussed.</p