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Απολύμανση νερού με τη χρήση φωτοκατάλυσης: αδρανοποίηση της Klebsiella pneumoniae και επίδραση στο γενετικό υλικό της

Fraggedaki Antonia

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URI: http://purl.tuc.gr/dl/dias/D5447383-3933-4CE7-A0D7-B13B23E32E27
Year 2014
Type of Item Master Thesis
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Summary

Klebsiella pneumoniae is considered an emerging pathogen persistent in extreme environmental and stressed conditions. The aim of the present study is the investigation of inactivation rates of this pathogen in water by means of heterogeneous photocatalytic treatment under simulated solar irradiation and the induced genetic variance applying RAPD-PCR as a molecular typing tool. For this purpose, novel Mn-, Co- and Mn/Co-doped TiO2 catalysts were assesed. The effect of various operating conditions was examined. The reference strain of K. pneumoniae proved to be readily inactivated, since disinfection occurred rapidly (i.e. after only 10 min of treatment) and low levels of bacterial regrowth were recorded in the dark and under natural sunlight. The activity of these catalysts was superior to the respective of commercially available P25 titania, accredited to the fact that they can be activated in the visible part of the spectrum, in the absence of UV light (i.e.>420 nm). Binary doped titania exhibited the best photocatalytic activity verifying the synergistic effect induced by composite dopants. Inactivation of the bacteria is attributed to the oxidative degradation of their cells and increase of their cell permeability and not to the potential toxicity of the metal-doped semiconductors, which did not exhibit any bactericidal properties. RAPD analysis showed that increasing the treatment time led to a considerable alteration of RAPD profiles. Genetic variation among isolates increased in relation to the period of treatment and prolonged irradiation in each case affected the overall alteration in band patterns. RAPD patterns were highly diverse between treated and untreated isolates when disinfection was performed with the Co-doped titania. The broad spectrum of genetic variance and generated polymorphisms has the potential to increase the already significant virulence of the species.

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