1994 Fiscal Year Final Research Report Summary
Development of Sterilization Strategy for Thermoduric Bacterial Spores in Photoreaction System with Solar Source
| Project/Area Number |
05555222
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| Research Category |
Grant-in-Aid for Developmental Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
生物・生体工学
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| Research Institution | Osaka University |
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Principal Investigator |
TAYA Masahito Osaka Univ., Dept.of Chem.Eng., Associate Professor, 基礎工学部, 助教授 (60144127)
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| Co-Investigator(Kenkyū-buntansha) |
NAGAI Naoshi Suntory Ltd., Institute for Fundamental Research Researcher, 基礎研究所, 研究員(研究者)
MASAWAKI Teruyuki Osaka Univ., Dept.of Chem.Eng., Assistant, 基礎工学部, 助手 (10209421)
TONE Setsuji Osaka Univ., Dept.of Chem.Eng., Professor, 基礎工学部, 教授 (40029418)
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| Project Period (FY) |
1993 – 1994
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| Keywords | Photoreactor / Photocatalytic Sterilization / Titanium Oxide / Saccharomyces cerevisiae / Escherichia coli / Bacillus stearothermophilus |
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| Research Abstract |
In the photocatalytic sterilization system using the semiconductive photocatalysts, it was found that the effective sterilization of microbes could be obtained with TiO_2 particles. In this study, different types of microbes namely, S.cerevisiae (cells) , E.coli (cells) and B.stearothermophilus (spores) were used. The sterilization of these microbes were performed in either the TiO_2 suspended or immobilized system and the following findings were obtained :
1.The presence of TiO_2 particles and dissolved oxygen was necessary in order to obtain the effective deactivation rate of spores/cells in a system illuminated with a high pressure Hg lamp (wavelengthrange : 365-579nm) .
2.Spore deactivation rates were promoted with the increase in the average light intensities inside the photoreactor. In addition, the dissolved oxygen was presumed to provide the formation of oxidative radicals which subsequently attacked the spores/cells.
3.The spore/cell deactivation kinetics could be described by ap
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plying the second-order reaction rate equation with respect to the concentrations of cells and oxidative radicals generated by light excitation of TiO_2 particles. Further, the effect of light intensity on spore/cell deactivation rates was expressed quantitatively based on a single-hit multitarget model or a series-event model.
4.To achieve the continuous sterilization, TiO_2 particles were immobilized on a glass plate surface and the photocatalytic sterilization experiment of E.coli was performed. It was then found that the effective rate of sterilization was obtained even with the TiO_2 immobilized system, and that the values of parameteres obtained from the kinetic analyzes based on a series-event model were identical in both the TiO_2 suspended and immobilized systems.
5.A linear relation was obtained between the apparent deactivation rate constant and light intensity in both the TiO_2 suspended and immobilized systems. It was also found that there existed a maximum value for the apparent deactivation rate constant with respect to TiO_2 concentration or its amount immobilized.
In conclusion, photochemical sterilization with semiconductive photocatalysts was effective for various types of microbes. A basic knowledge on the continuous operation of microbe sterilization could be obtained in the TiO_2 immobilized system. Less
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