Photo-Inactivation kinetics and mechanisms of Klebsiella pneumoniae and Aspergillus niger using visible-light-responsive photocatalyst.

• Main Authors: Ya-Zhen Huang, 黃雅甄
• Other Authors: 林耀東
• Format: Others
• Language: zh-TW
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/42649160849503241179

碩士 === 國立中興大學 === 土壤環境科學系所 === 105 === According to the investigation report from World Health Organization (WHO) and the United Nations Environment Program (UNEP), with the number of bacteria being ∼139 CFU cm-2 in the countryside and 72,110 CFU cm-2 in an urban environment(Peng, et al. 2008). Among them, some pathogenic strains such as Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae were caused infectious diseases ; some fungus such as Aspergillus niger and Aspergillus flavus are easy to caused food and environmental pollution (Zhang, et al. 2012). Due to traditional disinfection techniques produce toxic and carcinogenic substances in sterilization and antibacterial processes, such as iodide, derivatives of phenol, dibutyl phthalate, trihalomethanes and haloacetic acids. Therefore, development of new anti-bacteria (fungus) green materials is the top priority issue for today. In this research, homemade N-TiO2, N-T-TiO2, C-TiO2 and Pd-C-TiO2 were carried out photocatalytic deactivated under visible light irradiation. The inactivation reaction parameters including photocatalyst dose, the bacteria initial concentration and light intensity. The bioindicators were Klebsiella pneumoniae and Aspergillus niger. The experimental data were used to simulate the deactivation efficiency of the above-mentioned indicators strain by using the (Chick-Waston model, Modified Hom model, Light Chick-Waston model and Light Modified Hom model). The results showed that when the four photocatalytic materials were 1.0 g L-1 and 0.5%, the light intensity was 7.32 mW cm-2, and the initial bacterial concentrations were 105 CFU mL-1 and 105 spore # mL-1 can effectively make Klebsiella pneumoniae (1440 minutes) and Aspergillus niger (168 hours) reach 99.999% of the antibacterial rate. The antibacterial efficiency of each material on Klebsiella pneumoniae / Aspergillus niger was Pd-C-TiO2> C-TiO2> N-T-TiO2> N-TiO2. Effects of different microbial species on anti-photocatalytic deactivation with these four kinds of photocatalytic materials, Klebsiella pneumoniae (Pd-C-TiO2, 210 min) was lower than that of Aspergillus niger (Pd-C-TiO2, 96 hours). According to the electron micrograph of this study and predecessors studies, it was found that the cell wall of Aspergillus niger was thicker than Klebsiella pneumoniae, so the efficiency of inactivation was lower than that of Klebsiella pneumoniae under the same conditions. Chick-Waston model, Modified Hom model, Light-Chick-Waston model, and Light-Modified Hom model showed the potential to fit the experimental data and k values are regular, if the use of Modified Hom model for Klebsiella pneumoniae and Aspergillus niger simulation operation, showing the two photocatalytic deactivation reaction of the three-phase parameter changes are consistent. The trend of the first stage (buffer period) inactivation rate constant (k1) tends to rise; the second stage (logarithmic period) inactivation rate constant (k2) tends to rise; the third stage (lag phase) inactivation rate Constant (k3) value tends to decline. In this research, SEM, TEM, TXM and AFM were used to investigate the changes of cell surface and morphology in the photocatalytic deactivation of Klebsiella pneumoniae and Aspergillus niger during photocatalytic deactivation of modified titanium dioxide, and the mechanism of photocatalytic deactivation were explored by the release of K+, CoA, MDA, DNA and protein. The results of this research show that the homemade photocatalyst titanium dioxide has a high efficiency of antibacterial activity with the bioindicators such as Klebsiella pneumoniae and Aspergillus niger can reach 99.999% antibacterial rate and no traditional energy consumption, resulting in toxic byproducts and other shortcomings. In the future, these four materials can be widely used in anti-(fungi) and environmental anti-bacterial technology level and a high potential for development.