La qualité microbiologique de l’eau potable peut fortement se dégrader au cours de son transport dans les réseaux de distribution en raison notamment du détachement de bactéries présentes au sein de biofilms qui se développent inévitablement à la surface interne des canalisations. Cette étude développe une approche originale consistant à évaluer in situ et en temps réel la stabilité microbiologique d’une eau via l’empreinte spectrale infrarouge (IR) en mode réflexion totale atténuée (ATR) d’un jeune biofilm de référence constitué d’une monocouche de bactéries. Pseudomonas fluorescens a été choisie comme bactérie modèle. Ses signatures spectrales, infrarouge et Raman, ont été étudiées dans un premier temps à l’état planctonique et ce en fonction de la phase de croissance et de l’état d’hydratation. Le suivi in situ, via une cellule IR-ATR à circulation, des premières étapes de l’adhésion bactérienne, a ensuite permis de déterminer les conditions opératoires optimales de formation sur le cristal ATR du biofilm de référence. La structure de ce dernier a été caractérisée par microspectrométrie Raman et microscopie à épifluorescence. Enfin, la réponse du biofilm de référence exposé à des eaux contenant différentes quantités de carbone organique dissous (COD), facteur clé de la biostabilité d’une eau, a été analysée. Cette dernière partie montre très clairement la dynamique de croissance du biofilm et la corrélation entre les changements observés dans le profil spectral du biofilm naissant et les variations de la quantité de COD, et illustre le potentiel que pourrait présenter la méthode proposée en matière de gestion de la qualité microbiologique des eaux de distribution. / Drinking water biostability can evolve during its transport through distribution systems because of several factors. Bacterial biofilms which develop on the inner surface of pipes can detach and can consequently be a major source of contamination. This study evaluates the feasibility to assess, in real time, drinking water biostability by monitoring in situ the evolution of the Attenuated Total Reflectance – Fourier Transform InfraRed (ATR-FTIR) fingerprint of a nascent reference biofilm exposed to water under test. Pseudomonas fluorescens CIP 69.13 was chosen as the reference bacteria to form the monolayer reference biofilm. Its IR and Raman fingerprints were studied, in a first step, in planktonic state in accordance with growth phases and degree of hydration. Then, optimal experimental conditions were determined by following in situ and in real time the first steps of bacterial adhesion thanks to an ATR flow cell. Biofilm structure was characterised by Raman microspectroscopy and epifluorescence microscopy. Finally, the reference biofilm response was analysed when biofilm was exposed to different dissolved organic carbon (DOC) quantities in filtered drinking water. This parameter was chosen because its significant role in bacterial regrowth in drinking water distribution system. The last part clearly shows the dynamic response of biofilm growth and the relationship between the spectral profiles changes and DOC variations. Moreover, it illustrates the potential of the developed method to manage drinking water stability.

No description available.

No description available.

No description available.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Thèse (Ph. D.)--Université Laval, 2007. / Titre de l'écran-titre (visionné le 18 sept. 2007). Bibliogr.

Orientador: Marcelo Cristianini / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-03T20:56:17Z (GMT). No. of bitstreams: 1 Senatore_MarcelaAndreaDuranHaun_M.pdf: 684290 bytes, checksum: 522970fe79261c7d2890c0a19a39b587 (MD5) Previous issue date: 2004 / Resumo: Um dos problemas que enfrenta a indústria de laticínios é a recontaminação do leite decorrente da formação de biofilmes em tanques de armazenamento e trocadores de calor. A tecnologia de esterilização de materiais por gás plasma tem sido utilizada com sucesso na esterilização de instrumentos cirúrgicos, oftálmicos e dentários. Os objetivos deste trabalho foram avaliar a eficiência de um sistema de esterilização a gás plasma sob células de Pseudomonas fluorescens aderidas em placas de aço inoxidável utilizando o leite como substrato. Foram avaliadas as variáveis tempo de pré plasma, tempo de exposição ao plasma e potência do mesmo na remoção do biofilme. As placas de aço inoxidável com a bactéria aderida foram submetidas a um tratamento com gás plasma, que foi formado a partir de um produto comercial composto por ácido peracético, peróxido de hidrogênio e ácido acético. Dois sistemas modelo foram utilizados para simular a formação de biofilmes de Pseudomonas fluorescens, um dinâmico e outro estático, simulando trocadores de calor e tanques de armazenamento, respectivamente. Através do modelo estático foi possível obter contagens acima de 105 UFC por placa de aço inoxidável, mesmo após três ciclos de lavagem das placas em água estéril sob agitação. Foi observado um efeito positivo na inativação de P. fluorescens em função do tempo de pré-plasma do sanificante. Exposições acima de 7 minutos foram capazes de produzir reduções superiores a dois ciclos logarítmicos na inativação do microrganismo. Através de um planejamento experimental fatorial 23 foi demosntrado que as variáveis tempo de pré-plasma, tempo de exposição ao plasma e potência do plasma apresentaram efeitos positivos na inativação de Pseudomonas fluorescens. O tempo de exposição (min.) apresentou o maior efeito na destruição da bactéria; mas sendo um pouco superior à potência do plasma (w) / Abstract: One of the problems that food industry is facing is the milk recontamination through biofims formation on storage tanks and heat exchanger. The technology of sterilization for materials through gas plasma has been used with succesfull for cirurgycal, ophathalmic and dentistry equipment. The goals of this work was to evaluate the efficiency of a gas plasma sterilization system on Pseudomonas fluorescens cells adhered on stainless steel plates using milk as substrate. Time of pre plasma, plasma exposition and potency (Watts) were evaluated as independent variables on cell destruction. The stainless steel plates were submitted to gas plasma treatment originated from a commercial product composed of peracetic acid, hydrogen peroxide and acetic acid. Two model systems were used to simulate a biofilm formation of Pseudomonas fluorescens, one dynamic and one static, in order to simulate heat exchangers and storage tanks, respectively. Through static model it was possible to get counts over 105 UFC/plate after washing three times using sterile water under stirring conditions. It was observed a positive effect on P. fluorescens inactivation by pre-plasma in a time dependent way. Expositions over seven minutes were capable to produce reductions higher than two logarithmic cycles on microorganism inactivation. A 23 factorial design indicated that the pre-plasma time, time exposition and potency showed positive effects on Pseudomonas fluorescens inactivation. Time exposition (min) was the most effective variable on bacteria destruction, being a little higher than plasma potency (w) / Mestrado / Mestre em Tecnologia de Alimentos

A 1.57 kb XhoI restriction fragment derived from the TOL plasmid pDKI was subcloned into the E. Coli plasmid pUC19. The complete nucleotide sequence of this XhoI fragment was determined using both the chemical cleavage and chain termination DNA sequencing methods.