O H2 pode ser obtido por processos biológicos, como a fermentação, conduzidos à temperatura e pressão ambientes. Para tal são utilizadas matérias-primas renováveis, ricas em carboidratos, como as biomassas lignocelulósicas e de algas. Estas biomassas têm estrutura química complexa e requerem uma etapa de pré-tratamento e/ou hidrólise antes da sua utilização na fermentação. Processos de hidrólise podem liberar, tanto monossacarídeos, quanto substâncias potencialmente inibidoras de fermentação. Esse estudo avaliou o efeito de 3 potenciais inibidores de fermentação (5-hidroximetilfurfural -HMF, ácido levulínico AL e ácido fórmico AF), derivados da hidrólise de biomassas. Ensaios cinéticos de fermentação em batelada foram realizados com o microrganismo produtor de H2, Clostridium beijerinckii Br21, utilizando glicose como fonte de carbono e diferentes concentrações de cada inibidor. O efeito do HMF, do AL e do AF foram avaliados nas faixas de concentração de 0,5 a 2,5 g/L, de 1,0 a 4,0 g/L, e de 0,5 a 2,0 g/L, respectivamente. Retiraram-se amostras do gás produzido e do líquido para estimar as velocidades específicas de produção de H2, do crescimento celular e de consumo de glicose, nos ensaios com e sem a presença de inibidor (controle). Foi observada inibição de todos os parâmetros avaliados, comparados ao controle. Houve um aumento do tempo para início da produção e diminuição do rendimento de H2 com o aumento da concentração de todos os inibidores. Os resultados das fermentações permitiram estimar a concentração dos compostos que inibem 50% a produção de H2, o crescimento celular e o consumo do substrato (CI50). Os valores de CI50 obtidos para a produção de H2 pelo HMF, AL e AF foram 0,89, 2,50 e 1,15 g/L, respectivamente. Para o crescimento celular a CI50 do HMF, AL e AF foram 1,42, 2,08 e 1,46 g/L, respectivamente. Para o consumo de substrato a CI50 foi 3,23, 3,79 e 0,43 g/L, para o HMF, AL e AF, respectivamente. As concentrações de CI50 para a produção de H2 foram testados em 2 microrganismos distintos, o C. beijerinckii Br21 e o Clostridium acetobutylicum ATCC 824, para fins comparativos. Assim pode-se verificar a inibição na produção de H2 no C. beijerinckii Br21 de 49,3, 48,7 e 51,3%, enquanto que o C. acetobutylicum ATCC 824 apresentou inibição de 45,5, 61,3 e 59,6%, para o HMF, AL e AF, respectivamente. Foi estimada também a concentração de compostos que inibem 25% a produção de H2, a CI25, a fim de realizar misturas com os inibidores e testá-las em ambos os microrganismos. Os valores obtidos de CI25 para HMF, AL e AF foram 0,66, 2,15 e 0,89 g/L, respectivamente. A partir desses valores foram feitas 4 misturas distintas: HMF+AL, HMF+AF, AL+AF e HMF+AL+AF. A inibição da produção de H2 a partir dessas misturas em C. beijerinckii Br21foram de 58,9, 58,4, 49 e 85,9%, enquanto que para o C. acetobutylicum ATCC 824 obteve-se os valores de 67,6, 66,6, 55,5 e 88,8%, para HMF+AL, HMF+AF, AL+AF e HMF+AL+AF, respectivamente. Portanto, pode-se notar que o C. acetobutylicum ATCC 824 mostrou ser mais sensível aos efeitos causados pelos inibidores, sendo que o HMF parece atuar mais sobre a produção de H2, enquanto que os ácidos têm efeito mais global no metabolismo da bactéria. Esses estudos mostraram os limites destes compostos, quando se deseja utilizar hidrolisados de biomassas como matéria-prima para a produção fermentativa do H2.pelas espécies de Clostridium estudadas. / H2 can be obtained by biological processes, such as fermentation, conducted at ambient temperature and pressure. Renewable raw materials like lignocellulosic and algae biomass, which are rich in carbohydrates, can be used for this purpose. These types of biomass have complex chemical structures and require a pretreatment and/or hydrolysis step before they are used in fermentation. Hydrolysis may release not only monosaccharides but also potentially fermentation-inhibiting substances. This study evaluates how three potential fermentation inhibitors (5-hydroxymethylfurfural (HMF), levulinic acid-(LA), and formic acid (FA) derived from algal biomass hydrolysis affect H2 production. Kinetic batch fermentation assays were performed by using the H2-producing microorganism Clostridium beijerinckii Br21, glucose as carbon source, and different concentrations of each inhibitor. The effect of HMF, LA, and FA on H2 production was evaluated for inhibitor concentrations ranging from 0.5 to 2.5 g/L, 1.0 to 4.0 g/L, and 0.5 to 2.0 g/L, respectively. Samples of the produced gas and liquid were taken to estimate the specific rates of H2 production, cell growth, and glucose consumption in the assays conducted in the presence or in the absence (control) of an inhibitor. Increasing inhibitor concentration delayed the onset of H2 production and diminished the H2 yield. The fermentation results allowed us to estimate the inhibitor concentration that inhibited 50% of the H2 production, cell growth, and substrate consumption rates, designated IC50. Concerning the H2 production rate, IC50 was 0.89, 2.50, and 1.15 g/L for HMF, LA, and FA, respectively. As for the cell growth rate, IC50 was 1.42, 2.08, and 1.46 g/L for HMF, LA, and FA, respectively. Regarding the substrate consumption rate, IC50 was 3.23, 3.79, and 0.43 g/L for HMF, LA, and FA, respectively. IC50 was also tested in the presence of C. beijerinckii Br21 or Clostridium acetobutylicum ATCC 824 and one of the inhibitors. The H2 production rate decreased by 49.3, 48.7, and 51.3% in the presence of C. beijerinckii Br21 and of HMF, AL, or AF, respectively. In the presence of C. acetobutylicum ATCC 824 and of HMF, AL, or AF, the H2 production rate reduced by 45.5, 61.3, and 59.6%, respectively. The inhibitor concentration that inhibited 25% of H2 production, IC25, was also determined so that mixtures of the inhibitors could be prepared and tested in the presence of the microorganisms. HMF, LA, and FA afforded IC25 of 0.66, 2.15, and 0.89 g/L, respectively. On the basis of these values, four different mixtures were prepared: HMF+LA, HMF+FA, LA+FA, and HMF+LA+FA. In the presence of C. beijerinckii Br21, HMF+LA, HMF+FA, LA+FA, and HMF+LA+FA inhibited H2 production by 58.9, 58.4, 49, and 85.9%, respectively, whereas in the presence of C. acetobutylicum ATCC 824, inhibitions were 67.6, 66.6, 55.5, and 88.8% respectively. Therefore, C. acetobutylicum ATCC 824 was more sensitive to the effects caused by inhibitors. HMF seemed to affect the H2 production rate more, whereas acids appeared to act more globally on bacterial metabolism. These results reveal the concentration limits of the tested inhibitors when biomass hydrolysates are employed as raw material for fermentative H2 production.

Un problème fondamental pendant l'évaluation in vitro de la toxicité de composés organiques volatils (COVs) est le manque de connaissance de l'évolution de la concentration des COVs à laquelle les systèmes vivants sont exposés au cours des études expérimentales. Ce travail présente un nouveau dispositif expérimental conçu pour étudier l'exposition des systèmes vivants aux COVs. Le dispositif est formé de deux compartiments séparés par une membrane hydrophobe poreuse et permet des durées relativement longues de manipulations sans restreindre la respiration cellulaire. Une modélisation théorique qui couple la conservation de masse et du moment entre les différentes phases et la respiration des cellules hybridomes (ATCC CRL-1606) au sein du dispositif a été développée. Le modèle permet de prédire l'évolution de la concentration des COVs, de l'oxygène et du dioxyde de carbone dans le dispositif. Les résultats simulés pour le transfert des COVs ont revélé une bonne concordance avec les résultats expérimentaux et ont montré que le type de membrane et son diamètre, le coefficient de partage des COVs et la hauteur de la phase liquide ont une influence significative sur l'évolution de la concentration de ceux-ci dans la phase liquide. Néanmoins la disponibilité de l'oxygène au niveau des cellules dépend principalement de la densité cellulaire initiale, de la vitesse spécifique de consommation de ce gaz et de la hauteur du liquide alors que les paramètres liés à la membrane ont une influence sur le contrôle du pH. / A major problem during in vitro evaluation of the toxicity of volatile organic compounds (VOC) is the lack of knowledge of the evolution of the concentration of such compounds during the course of experimental studies with living systems. This work presents the design of a novel experimental device for the study of cell culture exposure to VOCs. The device is made of two compartments separated by a porous hydrophobic membrane and allows relatively long durations of handling without restricting cellular breathing. A theoretical modeling which couples mass and moment conservation between the different phases inside the device with the breathing kinetics of hybridoma cells (ATCC CRL-1606) was developed. The model allows predicting the evolution of the concentration of the VOCs, the oxygen and the carbon dioxide inside the device. The simulations of the mass transfer of the VOCs simulated presented a good agreement with experiments and showed that the type of membrane and its diameter, the VOCs partition coefficient and the height of the liquid phase have a significant influence on the evolution of their concentration in the liquid phase. Nevertheless, the availability of oxygen for the cells depends mainly on the initial cellular density, the specific kinetics of consumption of this gas and on the height of the liquid phase, whereas the parameters related to membrane have an influence on the control of the pH.

The preservative challenge test is a regulatory requirement specified in various pharmacopoeias to determine the efficacy of preservatives. However, such testing is a labour-intensive repetitive task and often requires days before results can be generated. Microbial biosensors have the potential to provide a rapid and automated alternative to the traditional viable counting currently in use. However, the selection of appropriate promoters is essential. The bioluminescent reporter strains used in the current study comprise the Photorhabdus luminescence lux CDABE reporter genes under the control of five individual constitutive Escherichia coli promoters: outer lipoprotein (lpp); twin arginine translocase (tatA); lysine decarboxylase (ldc); lysyl t-RNA (lysS); and ribosomal protein (spc). The promoter plus lux CDABE constructs were cloned, ligated into the plasmid vector pBR322 and transformed into E. coli ATCC 8739. The bioluminescence intensity in the decreasing order of constitutive promoter was lpp > spc> tatA> ldc > lysS. The five biosensor strains tested successfully in PET assays and demonstrated accuracy with a minimum detection limit of 103 CFU/ml, a detection range of 6 orders magnitude, and yielded equivalent results to methods currently recommended by the pharmacopoeias. The bioluminescent biosensors were used to monitor the efficacy of preservatives; sorbic acid at concentrations of 0.031% to 0.2% at pH 5.0, and benzalkonium chloride at concentrations of 0.0062% to 0.00039% alone and in combination with 0.03% EDTA. The 99.9% percentage of bioluminescence reduction of tatA-lux, ldc-lux, lysS-lux, and spc-lux was statistically equivalent to the 3 log10 CFU/ml reduction as required by the Pharmacopeias’. Strong significant correlations between bioluminescence and the methods recommended by the pharmacopoeias were obtained when the biosensor strains were challenged with preservatives, for all except lpp-lux E. coli. The bioluminescence expressed by the lpp-lux biosensor was significantly lower during long-term stationary phase than it was for any of the other biosensors and was also significantly lower than for any of the other biosensors in the presence of preservatives. Since the plasmid copy number and viable counts for lpp-lux did not change under these conditions, it suggests that perhaps lpp-lux was down regulated under stress conditions. There were no statistically significant differences between the results of the bioluminescence assays and the results of the viable count and ATP chemiluminescence assay. Virtual foot printing (using Regulon DB database) demonstrated that two crp binding sites overlapping the -10 regions are located on the negative strand of the lysS promoter sequences and that one crp binding site is located in lpp. The biosensor strains ldc-lux exhibited levels of bioluminescence per cell significantly lower than spc in the presence of preservatives whilst there was a significant increase in bioluminescence per cell by tatA-lux under alkaline conditions (pH 8.9) during long-term stationary phase. Amongst the five biosensor strains tested in the current work, it was determined that the spc-lux strain would be the most attractive candidate for further work, since the bioluminescence expressed per cell was significantly greater, by 10-1000 times, than that expressed by the other four promoters when challenged with the preservatives tested with excellent significant correlations between bioluminescence expression and viable counts in the PET assays with the various preservatives in this study (R2: 8.79-1.00). The bioluminescent biosensor strains showed no statistical differences from the control strains (wildtype E.coli ATCC 8739 and E.coli carrying a promoterless [pBR322.lux] for adneylate energy charge (AEC), plasmid copy number (PCN) bioluminescence or viable counts over 28 days. The emission of bioluminescence by the four bioreporter strains across 28 days is reflected by the stability of PCN with correlations of 0.78-0.90, except for lpp-lux with R2: 0.59. The following promoter elements were found likely to assist greater expression of bioluminescence: an A+T level of approximately 50% between the -40 and -60 regions (the UP element); a G+C level of approximately 50% within the -10 and +1 regions; the extended -10 region and -10 region of consensus sequence RpoD (σ70/D).

Siderophores are low molecular weight, iron chelating compounds produced by many bacteria for uptake of iron in case of iron scarcity. Vicibactin is a trihydroxamate type siderophore produced by Rhizobium leguminosarum bv. trifolii ATCC 14479. This work focuses on identifying an outer membrane receptor involved in the transport of vicibactin. We have confirmed the presence of the putative fhuA gene in R. leguminosarum bv. trifolii ATCC 14479. This bacteria shows mutualistic symbiosis with the red clover plant Trifoliium prantense. Leghemoglobin, with its cofactor heme is present in the plant root nodules that surrounds the infecting organism present in the nodules. This work attempts to elucidate the ability of Rhizobium leguminosarum bv. trifolii ATCC 14479 to utilize heme-bound iron and genes involved in the transport. We have also elucidated the role of energy transducing proteins TonB- ExbB-ExbD on the heme-bound iron uptake system.

Increasing consumer demand for new products with high nutritional qualities has spurred a search for new alternatives to food preservation. Pulsed electric field (PEF) is an emerging technology for non thermal food pasteurisation. Using this technology, enzymes, pathogenic and spoilage microorganisms can be inactivated without affecting the colour, flavour, and nutrients of the food. PEF treatment may be provided by applying pulsed electric field to a food product in a treatment zone between two electrodes at ambient , or slightly above ambient temperature. Exposure of microbial cells to the electric field induces a transmembrane potential in the cell membrane, which results in electroporation (the permeabilization of the membranes of cells and organelles) and/or electrofusion (the connection of two separate membranes into one) of the cells. An innovative pulsed electric field (PEF) unit was designed and constructed in the University of Auckland using modern IGBT technology. The system consists of main equipments, the high voltage pulse generator and the treatment chambers. The main focus of this work was to design an innovative PEF treatment chamber that provide uniform distribution of electric field, minimum increase in liquid temperature, minimum fouling of electrodes and an energy efficient system. Four multi pass treatment chambers were designed consisting of two stainless steel mesh electrodes in each chamber, with the treated fluid flowing through the openings of the mesh electrodes. The two electrodes are electrically isolated from each other by an insulator element designed to form a small orifice where most of the electric field is concentrated. Dielectric breakdown inside the chambers was prevented by removing the electrodes far from the narrow gap. The effect of the chambers different geometries on the PEF process in terms of electric parameters and microbial inactivation were investigated. Electric field intensity in the range of (17-43 kV/cm) was applied with square bipolar pulses of 1.7 µs duration. The effect of PEF treatment on the inactivation of gram-negative Escherichia coli ATCC 25922 suspended in simulated milk ultra-filtrate (SMUF) of 100%, 66.67% and 50% concentration was investigated. Treatments with the same electrical power input but higher electric field strengths provided larger degree of killing. The inactivation rate of E coli was significantly increased with increasing the electric field strength, treatment time and processing temperature. Morphological changes on E coli as a result of PEF treatment were studied under transmission electron microscopy (TEM). Significant morphological changes on E coli after PEF treatment were observed. The TEM studies suggested that the microbial inactivation was a consequence of electroporation and electrofusion mechanisms. Kinetic analysis of microbial inactivation due to PEF and thermal treatment of E coli suspended in SUMF were also studied. Comparison between measured (experimental) and predicted (theoretical) variation of E coli concentration with time following the PEF treatment was discussed, taking into consideration the recirculation mode of the PEF treatment. The treated liquid was circulated more than once through the treatment chamber to provide higher microbial inactivation. Arrhenius constants and activation energies of E coli inactivation using combined PEF and thermal treatment were calculated and generalized correlation for the inactivation rate constant as a function of electric field intensity and treatment temperature was developed. / Fonterra Research Institute (NZ) and the Foundation for Research Science and Technology (NZ)

Increasing consumer demand for new products with high nutritional qualities has spurred a search for new alternatives to food preservation. Pulsed electric field (PEF) is an emerging technology for non thermal food pasteurisation. Using this technology, enzymes, pathogenic and spoilage microorganisms can be inactivated without affecting the colour, flavour, and nutrients of the food. PEF treatment may be provided by applying pulsed electric field to a food product in a treatment zone between two electrodes at ambient , or slightly above ambient temperature. Exposure of microbial cells to the electric field induces a transmembrane potential in the cell membrane, which results in electroporation (the permeabilization of the membranes of cells and organelles) and/or electrofusion (the connection of two separate membranes into one) of the cells. An innovative pulsed electric field (PEF) unit was designed and constructed in the University of Auckland using modern IGBT technology. The system consists of main equipments, the high voltage pulse generator and the treatment chambers. The main focus of this work was to design an innovative PEF treatment chamber that provide uniform distribution of electric field, minimum increase in liquid temperature, minimum fouling of electrodes and an energy efficient system. Four multi pass treatment chambers were designed consisting of two stainless steel mesh electrodes in each chamber, with the treated fluid flowing through the openings of the mesh electrodes. The two electrodes are electrically isolated from each other by an insulator element designed to form a small orifice where most of the electric field is concentrated. Dielectric breakdown inside the chambers was prevented by removing the electrodes far from the narrow gap. The effect of the chambers different geometries on the PEF process in terms of electric parameters and microbial inactivation were investigated. Electric field intensity in the range of (17-43 kV/cm) was applied with square bipolar pulses of 1.7 µs duration. The effect of PEF treatment on the inactivation of gram-negative Escherichia coli ATCC 25922 suspended in simulated milk ultra-filtrate (SMUF) of 100%, 66.67% and 50% concentration was investigated. Treatments with the same electrical power input but higher electric field strengths provided larger degree of killing. The inactivation rate of E coli was significantly increased with increasing the electric field strength, treatment time and processing temperature. Morphological changes on E coli as a result of PEF treatment were studied under transmission electron microscopy (TEM). Significant morphological changes on E coli after PEF treatment were observed. The TEM studies suggested that the microbial inactivation was a consequence of electroporation and electrofusion mechanisms. Kinetic analysis of microbial inactivation due to PEF and thermal treatment of E coli suspended in SUMF were also studied. Comparison between measured (experimental) and predicted (theoretical) variation of E coli concentration with time following the PEF treatment was discussed, taking into consideration the recirculation mode of the PEF treatment. The treated liquid was circulated more than once through the treatment chamber to provide higher microbial inactivation. Arrhenius constants and activation energies of E coli inactivation using combined PEF and thermal treatment were calculated and generalized correlation for the inactivation rate constant as a function of electric field intensity and treatment temperature was developed. / Fonterra Research Institute (NZ) and the Foundation for Research Science and Technology (NZ)

Increasing consumer demand for new products with high nutritional qualities has spurred a search for new alternatives to food preservation. Pulsed electric field (PEF) is an emerging technology for non thermal food pasteurisation. Using this technology, enzymes, pathogenic and spoilage microorganisms can be inactivated without affecting the colour, flavour, and nutrients of the food. PEF treatment may be provided by applying pulsed electric field to a food product in a treatment zone between two electrodes at ambient , or slightly above ambient temperature. Exposure of microbial cells to the electric field induces a transmembrane potential in the cell membrane, which results in electroporation (the permeabilization of the membranes of cells and organelles) and/or electrofusion (the connection of two separate membranes into one) of the cells. An innovative pulsed electric field (PEF) unit was designed and constructed in the University of Auckland using modern IGBT technology. The system consists of main equipments, the high voltage pulse generator and the treatment chambers. The main focus of this work was to design an innovative PEF treatment chamber that provide uniform distribution of electric field, minimum increase in liquid temperature, minimum fouling of electrodes and an energy efficient system. Four multi pass treatment chambers were designed consisting of two stainless steel mesh electrodes in each chamber, with the treated fluid flowing through the openings of the mesh electrodes. The two electrodes are electrically isolated from each other by an insulator element designed to form a small orifice where most of the electric field is concentrated. Dielectric breakdown inside the chambers was prevented by removing the electrodes far from the narrow gap. The effect of the chambers different geometries on the PEF process in terms of electric parameters and microbial inactivation were investigated. Electric field intensity in the range of (17-43 kV/cm) was applied with square bipolar pulses of 1.7 µs duration. The effect of PEF treatment on the inactivation of gram-negative Escherichia coli ATCC 25922 suspended in simulated milk ultra-filtrate (SMUF) of 100%, 66.67% and 50% concentration was investigated. Treatments with the same electrical power input but higher electric field strengths provided larger degree of killing. The inactivation rate of E coli was significantly increased with increasing the electric field strength, treatment time and processing temperature. Morphological changes on E coli as a result of PEF treatment were studied under transmission electron microscopy (TEM). Significant morphological changes on E coli after PEF treatment were observed. The TEM studies suggested that the microbial inactivation was a consequence of electroporation and electrofusion mechanisms. Kinetic analysis of microbial inactivation due to PEF and thermal treatment of E coli suspended in SUMF were also studied. Comparison between measured (experimental) and predicted (theoretical) variation of E coli concentration with time following the PEF treatment was discussed, taking into consideration the recirculation mode of the PEF treatment. The treated liquid was circulated more than once through the treatment chamber to provide higher microbial inactivation. Arrhenius constants and activation energies of E coli inactivation using combined PEF and thermal treatment were calculated and generalized correlation for the inactivation rate constant as a function of electric field intensity and treatment temperature was developed. / Fonterra Research Institute (NZ) and the Foundation for Research Science and Technology (NZ)

Increasing consumer demand for new products with high nutritional qualities has spurred a search for new alternatives to food preservation. Pulsed electric field (PEF) is an emerging technology for non thermal food pasteurisation. Using this technology, enzymes, pathogenic and spoilage microorganisms can be inactivated without affecting the colour, flavour, and nutrients of the food. PEF treatment may be provided by applying pulsed electric field to a food product in a treatment zone between two electrodes at ambient , or slightly above ambient temperature. Exposure of microbial cells to the electric field induces a transmembrane potential in the cell membrane, which results in electroporation (the permeabilization of the membranes of cells and organelles) and/or electrofusion (the connection of two separate membranes into one) of the cells. An innovative pulsed electric field (PEF) unit was designed and constructed in the University of Auckland using modern IGBT technology. The system consists of main equipments, the high voltage pulse generator and the treatment chambers. The main focus of this work was to design an innovative PEF treatment chamber that provide uniform distribution of electric field, minimum increase in liquid temperature, minimum fouling of electrodes and an energy efficient system. Four multi pass treatment chambers were designed consisting of two stainless steel mesh electrodes in each chamber, with the treated fluid flowing through the openings of the mesh electrodes. The two electrodes are electrically isolated from each other by an insulator element designed to form a small orifice where most of the electric field is concentrated. Dielectric breakdown inside the chambers was prevented by removing the electrodes far from the narrow gap. The effect of the chambers different geometries on the PEF process in terms of electric parameters and microbial inactivation were investigated. Electric field intensity in the range of (17-43 kV/cm) was applied with square bipolar pulses of 1.7 µs duration. The effect of PEF treatment on the inactivation of gram-negative Escherichia coli ATCC 25922 suspended in simulated milk ultra-filtrate (SMUF) of 100%, 66.67% and 50% concentration was investigated. Treatments with the same electrical power input but higher electric field strengths provided larger degree of killing. The inactivation rate of E coli was significantly increased with increasing the electric field strength, treatment time and processing temperature. Morphological changes on E coli as a result of PEF treatment were studied under transmission electron microscopy (TEM). Significant morphological changes on E coli after PEF treatment were observed. The TEM studies suggested that the microbial inactivation was a consequence of electroporation and electrofusion mechanisms. Kinetic analysis of microbial inactivation due to PEF and thermal treatment of E coli suspended in SUMF were also studied. Comparison between measured (experimental) and predicted (theoretical) variation of E coli concentration with time following the PEF treatment was discussed, taking into consideration the recirculation mode of the PEF treatment. The treated liquid was circulated more than once through the treatment chamber to provide higher microbial inactivation. Arrhenius constants and activation energies of E coli inactivation using combined PEF and thermal treatment were calculated and generalized correlation for the inactivation rate constant as a function of electric field intensity and treatment temperature was developed. / Fonterra Research Institute (NZ) and the Foundation for Research Science and Technology (NZ)

[pt] Os ensaios dielétricos em equipamentos para alta tensão em corrente alternada (ATCA) e corrente contínua (ATCC) requerem medições de grandezas elétricas, e as análises de desempenho dos equipamentos ensaiados são diretamente dependentes dos resultados obtidos por tais medições. Atualmente, para garantir a confiabilidade dos resultados dos ensaios, é necessário que a forma de onda da tensão aplicada ao equipamento esteja dentro dos níveis de distorção exigidos por norma. Para que ensaios possam ser realizados de forma normalizada, todos os parâmetros descritos na norma ABNT NBR IEC 60060-1:2013 devem ser monitorados durante os ensaios em ATCA e ATCC. Normalmente um Sistema de Medição para Alta Tensão (SMAT) é formado por um divisor de tensão, um cabo de transmissão e um multímetro de bancada, permitindo assim uma análise quantitativa da tensão de ensaio por meio da medição do valor eficaz e/ou do valor médio. Entretanto, esse SMAT é inadequado para o monitoramento de todos os parâmetros normalizados, restringindo sua aplicação a uma análise puramente quantitativa da tensão de ensaio. Deste modo, o objetivo desta dissertação foi o desenvolvimento e validação de algoritmos de medição que fossem capazes de estimar todos os parâmetros normalizados. Sua validação foi realizada mediante ensaios experimentais em alta e baixa tensão, assim como pelo processamento das formas de onda digitais padrão pertencentes ao rascunho da norma IEC 61083-4. Os resultados obtidos foram positivos e dentro de limites aceitáveis, possibilitando a implantação desses algoritmos de medição nos laboratórios de ensaios (AT1, AT2, AT3, LabUAT) do CEPEL. / [en] Dielectric tests on equipment with high voltage alternating current (HVAC) and direct current (HVDC) require measurements of electrical quantities, and the performance analysis of the tested equipment is directly dependent on the results obtained by those measurements. Currently, to ensure the reliability of the test results, the voltage waveforms applied to the equipment must be within the distortion levels required by standard. For tests to be performed in a standardized way, all parameters described in ABNT NBR IEC 60060-1: 2013 must be monitored during the HVAC and HVDC tests. Normally, a High Voltage Measurement System is formed by a voltage divider, a transmission cable and a multimeter, allowing a quantitative analysis of the test voltage by measuring the RMS value and/or mean value. However, this High Voltage Measurement System is inadequate for the monitoring all standard parameters, restricting its application to a purely quantitative analysis of the test voltage. Therefore, the objective of this dissertation was the development and validation of measurement algorithms that are able to estimate all the normalized parameters. Its validation was carried out through experimental tests in high and low voltage, as well as by the processing of the standard digital waveforms belonging to the draft of the standard IEC 61083-4. The results were positive and within acceptable limits, allowing the implementation of these measurement algorithms in CEPEL test (AT1, AT2, AT3, LabUAT) laboratories.

Rhizobium leguminosarum is a Gram negative, motile, nitrogen-fixing soil bacterium. Due to the scarcity of iron in the soil bacteria have developed a wide range of iron scavenging systems. The two types of iron scavenging systems used are indirect and direct. In-silico analysis of the genome identified a unique direct iron scavenging system the Hmu operon. This system has been identified in other closely related rhizobium species and is believed to be involved in utilizing heme compounds as a sole source of iron. We have attempted to characterize the role of the Hmu operon in iron utilization by monitoring the growth of R. leguminosarum ATCC 14479 in hemin supplemented media. Growth curves show that it is capable of using hemin as a sole source of iron. The outer membrane profiles were analyzed for the presence of hemin binding proteins.