Heating milk to high temperatures such as 140 ºC, as used in ultra high temperature (UHT) processing, causes physical and chemical changes in the milk. The production of a cooked flavour is a major change which reduces consumer acceptance of the UHT milk. It has been correlated with the formation of volatile sulphur compounds (VSCs) that result from milk proteins, principally the whey proteins β-lactoglobulin, containing the the sulphur amino acids cystine, cysteine and methionine. The VSCs in milk, whose concentrations are in the parts per billion to parts per million range, are highly reactive, easily oxidised, and sensitive to heat during thermal processing and analysis; this makes them a challenge to analyse. A sensitive method based on gas chromatography with pulsed flame photometric detection coupled with headspace sampling by solid phase microextraction (SPME/GC/PFPD) was developed to detect these compounds in commercial UHT milk and to investigate their production and disappearance during heating and storage. The SPME/GC/PFPD procedure was optimised using different extraction time (15 min, 30 min, & 60 min) – temperature (30 oC, 45 oC & 60 oC) combinations with CAR/PDMS fibre to obtain maximum sensitivity. A short extraction time (15 min) at low temperature (30 oC) was chosen to provide high sensitivity for detecting all VSCs in UHT milk without introducing artefactual VSCs. The extraction method and GC run time (16 min) make this method simple and fast. Nine VSCs were detected in commercial indirectly processed UHT milk, skim and whole. These are hydrogen sulphide (H2S), carbonyl sulphide (COS), methanethiol (MeSH), dimethyl sulphide (DMS), carbon disulphide (CS2), dimethyl disulphide (DMDS), dimethyl sulphoxide (DMSO), dimethyl sulphone (Me2SO2) and dimethyl trisulphide (DMTS). An additional unknown compound was detected but could not be identified by GC/MS because its concentration was below the detection limit of the MS detector. The concentrations of H2S, DMS and DMTS were higher than their threshold values indicating their importance in milk flavour, especially cooked flavour. Several attempts have been made to reduce the cooked flavour in UHT milk. In the current research, the use of hydrogen peroxide (H2O2) to oxidise the VSCs and thereby reduce cooked flavour was investigated. H2O2 is used as a milk preservative and is generally recognised as safe (GRAS) in USA. Several concentrations of H2O2 (0.001%, 0.005%, 0.01%, 0.02% & 0.03%) were added to milk to assess its effects on VSCs and on whey proteins denaturation in UHT milk. H2O2 effectively reduced the concentration of all VSCs, except DMDS which was increased, presumably by oxidation of MeSH. H2S was completely oxidised or reduced below its threshold value. Low concentrations of H2O2 (0.001% & 0.005%) had no effect on, or decreased, the extent of denaturation of β-lactoglobulin when added after or before processing, respectively. Some UHT plants use severe heating conditions, leading to high levels of denaturation of whey proteins, particularly β-Lg, the main source of the VSCs in milk. Correlations between heat severity, β-Lg denaturation and individual VSC generation were investigated in milk batch-heated at 80 oC and 90 oC, and UHT milk processed at 120-150 oC. In accordance with previous reports, β-Lg was more heat-sensitive than α-La. Only five VSCs were detected. The concentrations of H2S and MeSH correlated well with denaturation of β-Lg and α-La. DMS concentration correlated well with β-Lg in UHT milk but not in the batch-heated milk. CS2 did not show a good correlation with heat intensity and appeared to plateau out after a certain level of heating. Conversely, COS and MeSH seemed to require a certain minimum amount of heat before generation commenced; this corresponded to denaturation of β-Lg above 49% and 89% respectively at 80 oC. The higher concentrations of DMS and H2S in UHT milk compared with batch-heated samples having similar degrees of denaturation suggested other possible sources for their production and the importance of the heat severity in generating them. For example, at high heat intensity, S-methylmethionine and thiamine could be sources of DMS and H2S respectively. Furthermore, in whole milk as used in this work, milk fat globule membrane proteins are another source of VSCs. The outcome of this study will help UHT manufacturers to understand the production and disappearance of the VSCs in commercial UHT milk and how to adjust the processing conditions to avoid generation of cooked flavour. Additionally, the promising results of using low concentrations of H2O2 to oxidise the VSCs will provide the industry with another means of reducing cooked flavour. Before H2O2 use is implemented in UHT processing, future studies are required to evaluate all of its effects, including sporicidal effects. Overall, this study makes a contribution to finding a solution to the cooked flavour problem in UHT milk, thereby increasing market share of this milk in countries such as Australia, the UK and North America where cooked flavour is the main barrier to its consumer acceptance.

[Truncated abstract] Biogeochemical processes in seagrass sediments influence growth and nutrition of seagrasses. This thesis investigates the below-ground interactions between biotic and abiotic factors that influence seagrass nutrition and growth, with focus on a small species of seagrass, Halophila ovalis (R. Br.) Hook ƒ., from the Swan River Estuary, Western Australia. Seagrass showed significantly lower growth and an increase in leaf nitrogen and phosphorus concentrations with increased organic matter loading. With maximal light reduction, lower growth rates and average leaf weights were observed, and leaf nitrogen and phosphorus concentrations were higher. Light reduction was also shown to increase bioavailability of inorganic nutrients within porewater of seagrass sediment . . . Sulphide was hypothesised to have an inhibitory effect on nutrient uptake of Halophila ovalis. Below-ground sulphide inhibits the photosynthetic efficiency of photosystem II at sulphide concentrations greater than 1 mM. Sulphide exposure enhanced phosphate uptake, with no significant effect on ammonium uptake of H. ovalis. This thesis demonstrates that biogeochemical processes both constrain the potential growth of seagrasses and influence the nutrient status of seagrass tissue. Consideration of the influence of sulphide stress on seagrasses is likely to be particularly important for anthropogenically influenced aquatic systems, where inputs of organic matter are enriched relative to pristine ecosystems. A better understanding of biogeochemical processes will allow researchers to predict how future changes in sediment chemistry will influence seagrass meadows.

Thesis (M.Tech.: Radiography)-Dept. of Radiography, Durban University of Technology, 2006 xi, 86 leaves, Annexures A-Q / The study will determine the sulphur dioxide (SO2) levels in the x-ray department and evaluate it’s effects on the health of the radiology workers. The aim of the study is to mainly create awareness of occupational hazards posed by processing chemistry to radiology workers.

Thesis (MSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: The yeast Brettanomyces was isolated from beer in 1904 and associated with wine thereafter. A sporulating form, Dekkera, was discovered later. Brettanomyces bruxellensis produces high levels of volatile phenol off-flavours in wine. Sulphur dioxide (SO2) is the most widely used chemical preservative in wine. Yeasts have several mechanisms to cope with the SO2, namely Ssu1p, a membrane bound SO2 transporter; sulphite reduction, sulphite oxidation and acetaldehyde production. In unfavourable environmental conditions, certain yeasts can enter a viable-but-non-culturable (VBNC) state which is characterised by reduced metabolic rate, inability to reproduce on solid media and a reduction of cell size. VBNC can be triggered by chemical stress such as high SO2 levels. The objectives of this study were to examine the SO2 tolerance of B. bruxellensis and Saccharomyces cerevisiae, to quantify their rates of SO2 accumulation and efflux, determine the effect of SO2 on their energy metabolism and investigate if B. bruxellensis possesses an orthologue to S. cerevisiae SSU1. In this study, the identity of a number of Brettanomyces/Dekkera strains was confirmed using 5.8S rDNA-ITS RFLP analysis and DNA sequencing. Sporulation assays were used to confirm whether these strains belonged to the Dekkera or Brettanomyces genus. A method to accurately quantify SO2 in laboratory conditions was optimised. Molecular SO2 tolerance was tested by spotting fresh yeast cultures on media with SO2 and/or ethanol. Tolerance to SO2 and/or ethanol showed highly strain dependent results with S. cerevisiae showing the highest tolerance levels while B. bruxellensis tolerated SO2 and ethanol poorly but certain strains grew well with only SO2. The SO2 accumulation and efflux rates of 3 S. cerevisiae strains and 3 B. bruxellensis strains were determined. It was shown that the S. cerevisiae strains followed the same trends as previously found in literature whereas B. bruxellensis strains showed similar trends but displayed highly variable strain-dependent results. B. bruxellensis CB63 and S. cerevisiae VIN13 were investigated for their response to SO2 in two different media, TA and SWM, over a 48-hour and 32-day period respectively. Acetic acid, acetaldehyde, D-glucose, D-fructose (only in SWM) and ethanol (only in TA) were regularly monitored over the time course of each experiment. SO2 had the greatest impact on B. bruxellensis with decreased rates of glucose consumption and ethanol production as well as increased acetic acid. Acetaldehyde peaked shortly after SO2 addition with the subsequent restarting of sugar consumption for certain samples. This suggests that sufficient acetaldehyde was produced to bind free SO2 to reduce SO2 stress. Volatile phenols were quantified for day 32 of the SWM experiment. An increase of 4-ethyl guaiacol was correlated to higher molecular SO2 levels. SO2 negatively affected both yeasts energy metabolism, forcing the yeasts metabolism to adapt to ensure survival. In general, SO2 was shown to have a negative impact on all aspects of a yeasts growth and metabolism and that SO2 tolerance is highly strain dependent and a far more complicated characteristic than currently understood. / AFRIKAANSE OPSOMMING: Die gis Brettanomyces is in 1904 uit bier geïsoleer en daarna met wyn geassosieer. 'n sporulerende vorm, Dekkera, is later ontdek. Brettanomyces bruxellensis produseer hoë vlakke van vlugtige fenol afgeure in wyn. Swaweldioksied (SO2) is die mees gebruikte chemiese preserveermiddel in wyn. Giste het verskeie meganismes om SO2 te hanteer, naamlik Ssu1p, 'n membraan-gebonde SO2 transporter, sulfietvermindering, sulfiet-oksidasie en asetaldehiedproduksie. In ongunstige omgewingstoestande kan sekere giste 'n lewensvatbare, maar nie-kultiveerbare (LMNK)-toestand aanneem wat gekenmerk word deur verlaagde metaboliese tempo, onvermoë om voort te plant op soliede media en 'n vermindering van die selgrootte. LMNK kan veroorsaak word deur chemiese stres, soos hoë SO2-vlak. Die doelwitte van hierdie studie was om die SO2 -bestandheid van B. bruxellensis en Saccharomyces cerevisiae te ondersoek, hul spoed van SO2 -opneming/akkumulasie en -uitskeiding te kwantifiseer, die invloed van SO2 op energiemetabolisme te bepaal en te ondersoek of B. bruxellensis oor ‘n soortgelyke geen as die S. cerevisiae SSU1 beskik. In hierdie studie is die identiteit van 'n aantal Brettanomyces/Dekkera-stamme bevestig deur 5.8S rDNA-ITS RFLP-analise en DNA-opeenvolging te gebruik. Sporulasietoetse is gebruik om te bevestig of hierdie stamme aan die genus Dekkera of Brettanomyces behoort. 'n Metode om SO2 onder laboratoriumtoestande akkuraat te kwantifiseer, is geoptimiseer. Molekulêre SO2- bestandheid is getoets deur vars giskulture op media met SO2 en/of etanol te groei. Bestandheid teen SO2 en/of etanol het stam-afhanklike resultate getoon, S. cerevisiae wat die hoogste toleransievlakke getoon het, terwyl B. bruxellensis SO2 en etanol swak tolereer, maar sekere stamme het goed gegroei met slegs SO2. Die SO2-akkumulasie en -uitskeidingtempo van 3 S. cerevisiae-rasse en 3 B. bruxellensis-stamme is bepaal. Daar is gevind dat die S. cerevisiae-rasse dieselfde tendens soos voorheen in die literatuur beskryf, gevolg het, terwyl B. bruxellensis-stamme soortgelyke tendense getoon het,maar hoogs veranderlike stamafhanklike resultate vertoon. B. bruxellensis CB63 en S. cerevisiae VIN13 is ondersoek vir hul reaksie tot SO2 in twee verskillende media, TA en SWM, oor 'n tydperk van 48-uur en 32-dae onderskeidelik. Asynsuur, asetaldehied, D-glukose, D-fruktose (slegs in SWM) en etanol (slegs in TA) is gereeld gemoniteer oor die verloop van elke eksperiment. SO2 het die grootste impak op B. bruxellensis met ‘n verlaagde tempo van glukoseverbruik en etanolproduksie, sowel as verhoogde asynsuur. ‘n Asetaldehiedhoogtepunt is bereik kort na die SO2-byvoeging met die daaropvolgende hervatting van suiker wat vir sekere monsters gebruik is. Dit dui daarop dat voldoende asetaldehied geproduseer is om vry SO2 te bind om SO2-stres te verminder. Vlugtige fenole is op dag 32 van die SWM-eksperiment gekwantifiseer. 'n Toename van 4-etiel-guajakol korreleer met hoër molekulêre SO2-vlakke. SO2 het beide giste se energiemetabolisme negatief beïnvloed, wat die gis dwing om sy metabolisme aan te pas om oorlewing te verseker. Oor die algemeen het SO2 'n negatiewe impak op alle aspekte van giste se groei en metabolisme, en SO2-bestandheid is hoogs stam–afhanklik. Dit is ook 'n baie meer ingewikkelde kenmerk as wat tans verstaan word.

This project was aimed to use a purple non-sulphur bacterium, Rhodopseudomonas palustris, as a biocatalyst for hydrogen production, from the waste of biodiesel manufacturing, crude glycerol. The goal of this project was to understand the fundamentals relevant to scaling up the process and developing an off the shelf product. The first objective was to determine the ability of R. palustris to generate hydrogen by non-growing cells in comparison to that by growing cells. Similar average hydrogen production rates and energy conversion were found for both processes but a significant difference in the hydrogen yield was observed. Hydrogen production reached ~ 80 % of the theoretical maximum hydrogen yield by non-growing R. palustris, about eight-fold of that reached by growing R. palustris. The high yield suggested that it is economically appealing to use non-growing R. palustris as the biocatalyst for continuous hydrogen production. To accomplish the proposed scale-up systems, understanding its product formation kinetics is the key. It was found that the hydrogen production rate is not growth-associated and depends solely on the dry cell mass with a non-growth associated coefficient of 2.52 (Leudeking–Piret model dP/dt=2.52 X). Light is vital for hydrogen production by non-growing R. palustris, in terms of light intensity and wavelength range. It was found that excessive or insufficient light intensity may constrain the performance. Only photons of light with appropriate wavelengths can excite cytochrome bacteriochlorophyll complexes II in R. palustris to generate hydrogen. Among white LEDs, infrared LEDs, and incandescent light bulbs, at the same light intensity, infrared LEDs gave the best results in the H2 production rate and energy conversion by non-growing cells, 22.0 % ± 1.5 % higher than that with white LEDs and around 25-30 times of that by incandescent light bulbs. It was found that non-growing R. palustris can be immobilised in alginate beads to give similar H2 production rates as that by cells suspended in media. This preliminary result pointed the direction of developing an off the shelf product of immobilised non-growing R. palustris as a biocatalyst for continuous hydrogen production.

O petróleo é uma complexa mistura de compostos orgânicos e inorgânicos em que predominam os hidrocarbonetos e que apresentam contaminações variadas, entre essas os compostos de enxofre. Esses além de gerarem inconvenientes durante os processos de refino do petróleo, como corrosão nos equipamentos e envenenamento de catalisadores dos processos de craqueamento, também representam um grande problema para o meio ambiente e para a saúde da população, principalmente em relação à poluição atmosférica. Além das emissões de compostos de enxofre oriundas da própria refinaria, com destaque para os óxidos de enxofre e o sulfeto de hidrogênio, os compostos de enxofre, que não são retirados durante o refino e estão presentes nos derivados do petróleo, provocam a emissão de uma grande quantidade de poluentes na atmosfera durante o processo de queima dos combustíveis. Os efeitos dos CRE na atmosfera urbana ainda não são muito conhecidos, o que justifica um estudo mais profundo desses compostos, que além de causarem danos a saúde da população, podem influenciar na formação do ozônio troposferico / Oil is a complex mixture of organic and inorganic compounds predominantly hydrocarbons and contaminants that have varied between these sulfur compounds. These drawbacks besides generating processes during oil refining, such as corrosion of equipment and poisoning of catalytic cracking processes, also represent a major problem for the environment and health of the population, especially in relation to air pollution. Besides the emissions of sulfur originating from refinery itself, especially the oxides of sulfur and hydrogen sulfide, sulfur compounds, which are not removed during the refining and are present in the petroleum, cause the emission of a wide amount of pollutants in the atmosphere during the fuel combustion. The effects of the CRE in the urban atmosphere are not yet known, which justifies a deeper study of these compounds, which, and to harm the health of the population, may influence the formation of tropospheric ozone

Made available in DSpace on 2014-06-11T19:28:23Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-05-22Bitstream added on 2014-06-13T20:18:05Z : No. of bitstreams: 1 marchizeli_pca_me_jabo.pdf: 379771 bytes, checksum: 4ab368a5eecf24097fb6ff931d682d28 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / O presente estudo teve por objetivo avaliar o efeito do uso do gluconato de sódio e duas fontes de metionina em rações com diferentes níveis de metionina + cistina sobre o desempenho, qualidade dos ovos, integridade da mucosa intestinal e a excreção de nitrogênio de poedeiras comerciais. Foram utilizadas 480 poedeiras da linhagem Isa Brown, distribuídas em um delineamento inteiramente casualizado, em esquema fatorial 5 x 2 (5 níveis de metionina+cistina com 2 níveis de gluconato de sódio), e para estudar o efeito do gluconato de sódio sobre as duas fontes de metionina estudadas, optou-se por um esquema fatorial 2 x 2 (dois níveis de gluconato de sódio e duas fontes de metionina), com 5 repetições de 8 aves cada. As variáveis foram submetidas à análise de variância e posteriormente (em caso de significância estatística <0,001) realizadas análises de regressão pelo modelo polinomial linear e quadrático (SAS, 2002). A exigência de metionina+cistina para o melhor desempenho das poedeiras foram de 0,753% para consumo de ração, 0,738% para a produção de ovos, 0,758% para massa de ovos e 0,703% para conversão alimentar. As fontes de metionina não revelaram diferenças estatísticas. Conclui-se que o uso do gluconato de sódio não expressou resultado significativo estatisticamente nas variáveis analisadas, no entanto, a produção e massa de ovos, a conversão alimentar e a integridade intestinal mostraram-se com tendência de melhora. / One experiment was conducted to evaluate the effect of sodium gluconate and two sources of methionine and different levels of methionine + cistyne in laying hens diets, one egg quality, intestinal mucosal integrity and nitrogen excretion. It was used 480 Isa Brown laying hens, distributed at range in a factorial design 5 x 2 (5 levels of methinine + cistyne with 2 levels of sodium gluconate), and to study the effect of sodium gluconate on two sources of methionine, it was chosen a factorial design 2 x 2 (two levels of sodium gluconate and two sources of methionine), with 5 repetitions of 8 hens each. Variables was submitted to analyses of variance and subsequent (when the test had significant effect < 0,001) related regression analyses by linear and quadratic polynomial model (SAS, 2002). The requirement of methionine + cistyne for better performance of laying hens were 0,753% for feed intake, 0,738% for eggs production, 0,758% for egg mass and 0,703% for feed conversion. The sources of methionine did not show statistical difference. It was concluded that the use of sodium gluconate did not expressed significant statistical result in variables analyzed, however, egg production and mass, feed conversion and intestinal mucosal integrity tended to be better.

O petróleo é uma complexa mistura de compostos orgânicos e inorgânicos em que predominam os hidrocarbonetos e que apresentam contaminações variadas, entre essas os compostos de enxofre. Esses além de gerarem inconvenientes durante os processos de refino do petróleo, como corrosão nos equipamentos e envenenamento de catalisadores dos processos de craqueamento, também representam um grande problema para o meio ambiente e para a saúde da população, principalmente em relação à poluição atmosférica. Além das emissões de compostos de enxofre oriundas da própria refinaria, com destaque para os óxidos de enxofre e o sulfeto de hidrogênio, os compostos de enxofre, que não são retirados durante o refino e estão presentes nos derivados do petróleo, provocam a emissão de uma grande quantidade de poluentes na atmosfera durante o processo de queima dos combustíveis. Os efeitos dos CRE na atmosfera urbana ainda não são muito conhecidos, o que justifica um estudo mais profundo desses compostos, que além de causarem danos a saúde da população, podem influenciar na formação do ozônio troposferico / Oil is a complex mixture of organic and inorganic compounds predominantly hydrocarbons and contaminants that have varied between these sulfur compounds. These drawbacks besides generating processes during oil refining, such as corrosion of equipment and poisoning of catalytic cracking processes, also represent a major problem for the environment and health of the population, especially in relation to air pollution. Besides the emissions of sulfur originating from refinery itself, especially the oxides of sulfur and hydrogen sulfide, sulfur compounds, which are not removed during the refining and are present in the petroleum, cause the emission of a wide amount of pollutants in the atmosphere during the fuel combustion. The effects of the CRE in the urban atmosphere are not yet known, which justifies a deeper study of these compounds, which, and to harm the health of the population, may influence the formation of tropospheric ozone

Orientador: Andréa Balan Fernandes / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-17T16:02:06Z (GMT). No. of bitstreams: 1 Pegos_VanessaRodrigues_M.pdf: 19133775 bytes, checksum: abcda42c9097c7e59ea61175934c2304 (MD5) Previous issue date: 2011 / Resumo: A captação de sulfato em Escherichia coli é dependente do transportador do tipo ABC (do inglês, ATP Binding Cassete), SbpCysAWD, pertencente a um regulon que envolve 26 genes. Na ausência de sulfato, a bactéria induz a expressão de dois outros transportadores ABC, o de proteínas do sistema de transporte de alcanosulfonatos (SsuABCDE) e de sulfonatos alifáticos (TauABCDE), que são responsáveis pela captação, incorporação e oxidação destes compostos a sulfito e aldeído. Embora não comprovado funcionalmente, Xanthomonas axonopodis pv. citri apresenta todos os genes envolvidos neste regulon e, neste trabalho, dando continuidade à caracterização do transportador SsuABCDE, foi realizada pela primeira vez, a caracterização estrutural e funcional das enzimas SsuD e SsuE. Análises bioquímicas associadas às análises de bioinformática e modelagem molecular, revelaram que as enzimas SsuD e SsuE constituem um sistema de dois componentes, no qual a SsuD seria a óxido-redutase responsável pela oxidação do NAD(P)H, seguida da redução da FMN. A proteína foi expressa e purificada a partir de células de E. coli com massa molecular de 39 kDa, e se organiza na forma de um octâmero, conforme demonstrado por experimentos de espalhamento de raios X a baixo ângulo e ultra-centrifugação. O modelo da estrutura tridimensional da SsuD revela uma proteína com enovelamento barril-TIM, com conservação de resíduos que permitem a oligomerização e a interação com NAD(P)H, mas não com flavina. Ensaios enzimáticos mostraram que a SsuD liga NADP(Pbp) com alta afinidade (0,21 µM) e é capaz de oxidá-lo conforme os parâmetros cinéticos de Km: 0.1877 µM -1; Kcat: 7,192 s-1; Vmáx: 0.7911 µM/min; Kcat/Km: 3,8 x 107 m-1S-1. Ainda, foram obtidos cristais da SsuD em diferentes condições as quais estão em fase de refinamento. As análises de bioinformática da SsuE sugerem que ela seja a óxido-redutase do sistema. O trabalho ainda mostra a caracterização da proteína Pbp de X. axonopodis, do suposto sistema de transporte de fosfonatos. A Pbp foi expressa com massa molecular de 33 kDa, e as análises espectroscópicas revelaram alterações conformacionais na estrutura secundária na presença de fosfonatos e fosfato, bem como aumentada estabilidade térmica na presença de espermidina, usada nos ensaios de cristalização. Cristais foram obtidos em diferentes condições e devem ser usados para os testes de difração. Os resultados apresentados neste trabalho revelam dados de proteínas e sistemas de X. axonopodis ainda não estudados e serão importantes para direcionar futuros estudos sobre a função destas na bactéria, tanto em condições laboratoriais, como em testes in vivo, durante infecção na planta / Abstract: Sulfur uptake in Escherichia coli is dependent of the ABC transporter SbpCysAWD (ATP Binding Cassete), which belongs to a regulon with 26 genes. In the sulfate absence, the bacteria induces the expression of two other ABC transporters, for alkanesulfonates (SsuABCDE) and aliphatic sulfonates (TauABCDE), which are responsible for the uptake and oxidation of these compounds to sulfite and aldehyde. Although its functionality has been not showed, Xanthomonas axonopodis pv. citri has all the genes involved in this regulon, including the alkanesulfonate transporter and enzymes. In order to continue the characterization of this transport, this work shows for the first time, the structural and functional characterization of the proteins SsuD and SsuE. Biochemical analyses associated to the bioinformatics and molecular modeling tools revealed that the SsuD and SsuE form a two-components system, where SsuD is the oxidoreductase responsible for the NAD(P)H oxidation followed by the FMN reduction. The protein was expressed and purified from E. coli cells with a molecular mass of the 39 kDa and it is organized in a octamer, such was demonstrated by the small angle scattering X-ray and ultracentrifugation assays. The tri-dimensional model of SsuD reveals a TIM barrel folding and conservation of residues that allow the oligomerization and NADP interaction. Enzymatic assays showed a high affinity binding of SsuD and NADP (0,21 µM) and that the protein was able to obtain the cinetic parameters, such as Km: 0.1877µM -1; Kcat: 7,192 s-1; Vmáx: 0.7911 µM/min; Kcat/Km: 3,8x 10-7 m 1S-1. Indeed, SsuD crystals were obtained in different conditions. The work still shows the charactrization of the Pbp protein, from X. axonopodis, believed to be the fosfonate/fosfate binding protein. Pbp was expressed with a molecular mass of 33 kDa, and spectroscopic analyses revealed conformational changes at the secondary structure content in presence of fosfonates, as well as an increased thermal stability in presence of spermidine, which was used for the crystallization trials. Crystals were obtained but still not tested. All results presented in this work can bring some light to the strategies that X. axonopodis uses for growth and infection and they will direct our studies for laboratorial and in vivo analyses / Mestrado / Genetica de Microorganismos / Mestre em Genética e Biologia Molecular

A monoetanolamina (MEA) é um composto bifuncional pertencente à classe dos amino-álcoois, muito utilizado em processos industriais envolvendo a remoção de gases ácidos como SO2 , CO2 e H2S. A resina Amberlite XAD-7 é uma resina não-iônica de polaridade intermediária muito utilizada em procedimentos de pré-concentração de compostos orgânicos e íons metálicos. Neste trabalho, estudou-se a interação entre a superfície da resina XAD-7 e a MEA. Massas conhecidas da resina foram colocadas em contato com soluções de MEA em concentrações conhecidas, sob agitação durante certo intervalo de tempo. A quantidade de MEA adsorvida foi calculada considerando-se a diferença entre a concentração inicial e a concentração remanescente no sobrenadante, ambas obtidas a partir de medidas de absorbância, com utilização da reação de Berthelot modificada. Modelos cinéticos de pseudo-primeira e -segunda ordens, além do modelo de difusão intra-partícula, foram aplicados aos dados experimentais obtidos no estudo cinético. Entre estes modelos aplicados, o de pseudo-segunda ordem apresentou excelente ajuste aos dados experimentais. O estudo realizado em um determinado tempo de contato e variando-se a concentração inicial de MEA forneceu resultados experimentais que foram aplicados a três modelos de isotermas (Langmuir, Freundlich e Dubinin-Radushkevich). Destes ajustes, que mostraram excelente concordância, foram obtidos diferentes parâmetros termodinâmicos que definiram algumas características do processo de adsorção. Finalmente, estudos preliminares evidenciaram a retenção de SO32- na superfície da resina XAD-7 modificada com MEA, mostrando a possibilidade da utilização da XAD- 2 7/MEA para extração de SO32- presente em soluções ou de SO2 recolhido em solução alcalina. / Monoethanolamine (MEA) is a bifunctional compound which belongs to the amino- alcohol group, and it is widely used in industrial \"sweetening process\", which is based on the acidic gas (such as SO2 , CO2 and H2S) absorption. Amberlite XAD-7 is a non-polar resin with an intermediate polarity used to pre-concentrate organic compounds and transition metals. In this work, the interaction between the resin surface and MEA was studied. Known amounts of the resin were kept in contact with aqueous solutions of MEA and shaked under a constant rotation and during some defined intervals of time. The amount of adsorbed MEA was calculated as the difference between the initial concentration and remained concentration in the supernatant solution, which was determined applying the Berthelot´s reaction and the spectrophotometry. Kinetic models of pseudo-first and -second orders and intra-particle diffusion model were applied on experimental data collected from the kinetic study. Among these methods, the pseudo-second order model fulled fit on those experimental data. The experiments carried out under a constant time, but by changing the initial MEA concentration, led to other experimental data which were applied to three different isotherm models (Langmuir, Freundlich e Dubinin-Radushkevich). Each model showed a good fit, and for each one, different thermodynamic parameters were calculated and used to describe some adsorption characteristics. Finally, preliminary studies on the retention of SO32- onto the resin surface, previously modified with MEA, showed the possibility to extract SO32- found in aqueous solutions or SO2 recovered in alkaline media.