title: Probing the intracellular organic matters released from the photocatalytic inactivation of bacteria using fractionation procedure and excitation-emission-matrix fluorescence.
abstract: Photocatalysis provides a "green" and effective strategy for water disinfection. During the photocatalytic disinfection process, intracellular organic matter (IOM) from bacterial cells may be released into the bulk solution. In this study, the role of released IOM in the photocatalytic bacterial inactivation was investigated by fractionation procedure and fluorescence excitation-emission-matrix (EEM) combined with parallel factor analysis (PARAFAC) approaches. The normal bacterial cells treated by TiO2-UVA in the presence and absence with fractionated IOM results implied that the released IOM would be either absorbed on the surface of the photocatalysts or reacted by the photo-generated reactive species, and thereby affecting the kinetics of photocatalytic bacterial inactivation. Fluorescence EEM-PARAFAC results showed that two components (C1 and C3) associated with tryptophan- and tyrosine-like proteins were released. While another two components (C2 and C4) were the oxidation products, and their intensities were found to negatively correlate with those of C1 and C3, respectively. Microtox®test results indicated that toxicity occurred during the photocatalytic bacterial inactivation process. The toxicity was found to decrease after the bacteria were completely inactivated, and completely removed if provided a sufficient reaction time. Of particular interest is that a significant high linear correlation was observed between the toxicity and the maximum fluorescence intensity of C4. The results and information obtained in this study will be important for further developing photocatalysis in water/wastewater disinfection.
authors.affiliation: School of Life Sciences, The Chinese University of Hong Kong, Shatin, NT, Hong Kong, China.
authors.forename: Guocheng
authors.initials: G
authors.lastname: Huang
authors.affiliation: School of Life Sciences, The Chinese University of Hong Kong, Shatin, NT, Hong Kong, China.
authors.forename: Tsz Wai
authors.initials: TW
authors.lastname: Ng
authors.affiliation: Institute of Environmental Health and Pollution Control, School of Environmental Science and Engineering, Guangdong University of Technology, Guangzhou 510006, China. Electronic address: antc99@gig.ac.cn.
authors.forename: Taicheng
authors.initials: T
authors.lastname: An
authors.affiliation: Institute of Environmental Health and Pollution Control, School of Environmental Science and Engineering, Guangdong University of Technology, Guangzhou 510006, China.
authors.forename: Guiying
authors.initials: G
authors.lastname: Li
authors.affiliation: School of Life Sciences, The Chinese University of Hong Kong, Shatin, NT, Hong Kong, China.
authors.forename: Dehua
authors.initials: D
authors.lastname: Xia
authors.affiliation: School of Life Sciences, The Chinese University of Hong Kong, Shatin, NT, Hong Kong, China.
authors.forename: Ho Yin
authors.initials: HY
authors.lastname: Yip
authors.affiliation: Centre for Clean Environment and Energy, Griffith Scholl of Environment, Griffith University, Queensland 4222, Australia.
authors.forename: Huijun
authors.initials: H
authors.lastname: Zhao
authors.affiliation: School of Life Sciences, The Chinese University of Hong Kong, Shatin, NT, Hong Kong, China. Electronic address: pkwong@cuhk.edu.hk.
authors.forename: Po Keung
authors.initials: PK
authors.lastname: Wong
mesh_terms: D001419:Bacteria; D005591:Chemical Fractionation; D004203:Disinfection; D005163:Factor Analysis, Statistical; D013050:Spectrometry, Fluorescence; D062065:Wastewater
chemical_list: D062065:Wastewater
keywords: 3-D fluorescence; Escherichia coli; Fractionation procedure; Intracellular organic matters; Photocatalysis