Neste trabalho, os sistemas de eletrocatalisadores platina-rutênio (PtRu/C) e platina-estanho (PtSn/C) suportados em carbono de alta área superficial XC72R (Cabot) foram preparados pela redução química de precursores metálicos em solução usando o ácido cítrico como agente redutor. Os eletrocatalisadores foram preparados em diferentes valores de pH, com o objetivo de obter as condições de sínteses mais otimizadas para cada um dos sistemas preparados. O método otimizado mostrou-se eficiente na redução e ancoragem de todos os metais presente em solução, sendo possível preparar tanto catalisadores com baixos teores de segundo metal (razão atômica entre Pt:M = 90:10) quanto catalisadores com altos teores de segundo metal (Pt:M = 50:50). Os eletrocatalisadores obtidos foram caracterizados por espectroscopia de energia dispersiva de raios X, difração de raios X e microscopia eletrônica de transmissão. A atividade frente a eletro-oxidação de metanol e etanol foi avaliada através de voltametria cíclica e cronoamperometria em célula eletroquímica. Para os catalisadores com melhores desempenhos eletroquímicos foram realizados experimentos em célula a combustível unitária alimentada diretamente por metanol ou etanol. O desempenho dos eletrocatalisadores preparados foi comparado com o desempenho dos eletrocatalisadores comerciais Pt50Ru50/C e Pt75Sn25/C da linha HP (High Performance) fornecidos pela E-TEK, considerados como referência nos estudos frente a eletro-oxidação de alcoóis. Para eletro-oxidação do metanol foram obtidos eletrocatalisadores com desempenho comparável ao E-TEK e para eletro-oxidação de etanol foram obtidos eletrocalisadores com desempenho superior aos catalisadores E-TEK. / In this work, platinum ruthenium (PtRu/C) and platinum tin (PtSn/C) electrocatalysts were prepared by a chemical reduction process using citric acid as reducing agent and high surface area Vulcan Carbon XC72R (Cabot) as supports. The PtRu/C and PtSn/C catalysts were characterized by energy dispersive X-ray spectroscopy, X-ray diffraction and transmission electron microscopy. The electro-oxidation of methanol and ethanol were studied at room temperature by cyclic voltammetry and chronoamperometry. Single fuel cell experiments were carried at 90 °C and the performance of the homemade electrocatalysts prepared by citric acid method in optimized conditions were compared with commercial Pt50Ru50/C and Pt75Sn25/C E-TEK HP (High Performance) catalysts. For methanols electro-oxidation electrocatalysts with comparable E-TEKs catalysts performance were obtained and for ethanols electro-oxidation electrocatalysts with superior performance than E-TEKs electrocatalysts were obtained.

Resultados de pesquisas prévias tem encontrado potencial aumentado para a consolidação de enxertos ósseos mediante desmineralização do material enxertado e/ou das superfícies de consolidação. Entretanto há carência de embasamento apoiado em evidências biológicas do benefício de tal procedimento. Para testar esta hipótese, o tecido ósseo da calvária de cobaias (Cavia porcellus) foi exposto ao condicionamento por ácido cítrico durante 15, 30, 90 e 180 segundos (grupos teste). Quarenta e cinco discos ósseos de três milímetros de diâmetro foram removidos dos animais, dos quais 36 foram condicionados com ácido cítrico pH 1 a 50% e nove não receberam condicionamento (grupo controle). Sobre nove discos de cada grupo foram cultivados pré-osteoblastos MC3T3-E1 durante 24, 48 e 72 horas (três discos de cada grupo em cada tempo). Análises da morfologia celular, do número de células aderidas sobre as superfícies e da área de cobertura destas superfícies por préosteoblastos foram realizadas à microscopia eletrônica de varredura. Observou-se aumento do número de células aderidas às superfícies com o tempo, independentemente de haver condicionamento ou de seu tempo de aplicação. Entretanto, essa diferença só foi estatisticamente significante intragrupos (p<0,05) e quando comparados os períodos de 24 e 72 horas de incubação. A área de cobertura das superfícies por células aumentou significantemente com o tempo somente nos grupos teste, também entre os períodos de incubação de 24 e 72 horas (p<0,01). O grupo controle apresentou-se com 50% ou menos de área de cobertura superficial em relação aos demais. A duração de aplicação do ácido não interferiu significantemente nesse parâmetro de avaliação, mas nos grupos 15 e 30, a área de recobrimento ósseo mais do que triplicou às 72 horas em relação às 24 horas (p<0,01), com cerca de 70% das superfícies cobertas por células, contra 30% no grupo controle. Conclui-se que a desmineralização óssea nos tempos de condicionamento estudados propicia um substrato sobre o qual as células pré-osteoblásticas adquirem morfologia compatível com estágio de diferenciação mais avançado, promovendo maior cobertura de área, o que aumenta o potencial para deposição de novo osso sobre essas superfícies em comparação ao tecido não condicionado. / Results of previous research has found increased potential for the consolidation of bone grafts by demineralization of the graft material and / or areas of consolidation. However there is a lack of foundation supported by biological evidence of benefits from such procedures. To test this hypothesis, the bone tissue of the calvaria of guinea pigs (Cavia porcellus) were exposed to conditioning by citric acid for 15, 30, 90 and 180 seconds (test group). Forty-five bone disks measuring three millimeters in diameter were removed from the animals, of which 36 were conditioned with citric acid pH 1 to 50% and nine did not receive conditioning (control group). About nine disks in each group were pre-cultured with MC3T3- E1 osteoblasts for 24, 48 and 72 hours (three discs of each group at each time point). Analysis of cell morphology, number of cells attached on the surface and the coverage area of these surfaces by pre-osteoblasts were performed on scanning electron microscopy. There was na increase in the number of cells attached to surfaces over time, regardless of conditioning or application time. However, this difference was not statistically significant intra-group (p <0.05) when comparing the periods of 24 and 72 hours of incubation. The coverage area of the surfaces of cells increased significantly with time only in the test groups, also among the incubation periods of 24 and 72 hours (p <0.01). The control group presented with 50% or less of surface area coverage compared to the other. The duration of application of the acid did not affect significantly this parameter of evaluation, but in groups 15 and 30, the bonearea covered more than tripled from 24 to 72 hours (p <0.01), with about 70 % of the area covered by cells, versus 30% in the control group. It was concluded that bone demineralization in the studied conditioning times provides a substrate on which cells acquire pre-osteoblastic morphology compatible with more advanced stage of differentiation, promoting greater coverage area, which increases the potential for deposition of new bone on these surfaces compared to the tissue-air basis.

Este trabalho teve por objetivo estudar a capacidade da remoção da camada de smear das paredes do canal radicular, pelas soluções de EDTA a 15%, ácido cítrico a 10%, citrato de sódio a 10%, vinagre de maçã, ácido acético a 5%, ácido málico a 5% e hipoclorito de sódio a 1% por meio da microscopia eletrônica de varredura e quantificar a concentração de ions cálcio presentes nessas soluções após suas utilizações, por meio da espectrofotometria de absorção atômica de chama. Utilizaram-se 42 dentes incisivos centrais superiores, nos quais se realizou a cirurgia de acesso, remoção de ombro cervical e desgaste compensatório. Aferiu-se o comprimento de trabalho com uma lima tipo K, diâmetro #10 introduzida no canal radicular de cada dente até ser visualizada no ápice, subtraindo-se um milímetro. Determinou-se também o diâmetro anatômico do canal do dente no comprimento de trabalho por meio da introdução de instrumentos tipo K da primeira série com diâmetros sucessivamente maiores, que foi anotado quando um dos instrumentos sofresse resistência ao ser retirado do comprimento de trabalho. Todos os dentes que apresentaram diâmetro anatômico do canal acima de 40 centésimos de milímetros foram descartados e repostos por outros. Desta forma, garantiu-se o desgaste de 20 centésimos de milímetros no terço apical. A técnica utilizada foi a Free Tip Preparation (PECORA et al. 2002) até que um instrumento de diâmetro #60 e taper .04 percorresse todo o comprimento de trabalho. Utilizou-se a solução de hipoclorito de sódio a 1,0% durante todo o preparo biomecânico. Os dentes tiveram seus canais radiculares lavados com 20 mililitros de água deionizada para a remoção de possíveis raspas de dentina soltas no interior do canal radicular. Após o término do preparo biomecânico, os dentes foram divididos aleatoriamente em 7 grupos de 6 dentes cada, de acordo com a substância química utilizada para a irrigação final, a saber: G1 - solução de EDTA a 15,0%; G2 - solução de ácido cítrico a 10,0%; G3 - solução de citrato de sódio a 10,0%; G4 - vinagre de maçã; G5 - solução de ácido acético a 5,0%; G6 - solução de ácido málico a 5,0% e G7 - sem irrigação final (controle negativo). O tempo de permanência das soluções nos canais radiculares foi de 5 minutos. Os dentes foram clivados no sentido vestíbulo-palatino e encaminhados para a microscopia eletrônica de varredura, em que se obtiveram fotomicrografias com o aumento de 1000 vezes. As soluções coletadas foram encaminhadas para a análise química, realizada com um espectrofotômetro de absorção atômica de chama. Concluiu-se que o EDTA a 15% e o ácido cítrico a 10% são eficientes para a remoção da camada de smear. O vinagre de maçã, o citrato de sódio a 10%, os ácidos acético e málico a 5% e o hipoclorito de sódio não foram eficientes para a mesma finalidade. O EDTA a 15% apresentou a maior concentração de ions cálcio em solução; o ácido cítrico a 10% ficou na segunda posição e a terceira foi ocupada pelo vinagre de maçã e os ácidos acético e málico a 5%. A menor concentração de íons cálcio foi encontrada no citrato de sódio a 10%. / This study evaluated the smear layer removal capacity of 15% EDTA, 10% citric acid, 10% sodium citrate, apple vinegar, 5% acetic acid and 1% sodium hypochlorite using scanning electron microscopy and flame atomic absorption spectrophotometry. Forty two central superior incisives were used. On these teeth, it were accomplished the access surgery, removal of cervical shoulder and compensatory wear. The working length was checked with a #10 K-type file that was introduced in the radicular canal of each tooth until be visualized at the apex, then a millimeter was subtracted. The anatomical diameter of the canal in the working length was also determined through the introduction of K-type instruments of the first series with successively larger diameters. The anatomical diameter of the radicular canal was notated when one of the instruments showed resistance to be removed from the working length. All the teeth that presented the canal diameter in the working length above 40 hundredths millimeters were discarded and replaced by other. This way, it was obtained a standard wear of 20 hundredths millimeters in the apical third. The Free Tip Preparation technique (PECORA et al. 2002) was used until a #60- diameter instrument and .04 taper reached the entire working length. The 1.0% sodium hypoclorite solution was used during biomechanical preparation. The teeth had their radicular canals washed with 20 milliliters of deionized water, using Milli-Q® water purification system, for removal of possible dentine chips presented inside the root canal. After the biomechanical preparation, the teeth were randomly divided into 7 groups of 6 teeth each: group 1: teeth with final irrigation with 15% EDTA solution, group 2: teeth with final irrigation with 10%citric acid solution, group 3: final irrigation with 10% sodium citrate solution, group 4: final irrigation with apple vinegar, group 5: final irrigation with 5% acetic acid solution, group 6: final irrigation with 5% maleic acid solution and group 7: teeth only instrument and irrigated with sodium hypochlorite, without final irrigation. Each solution remained 5 minutes in the radicular canal. The cleavage of teeth was done in buccal-palatine direction and they were subjected to the scanning electron microscopy and photographed at 1000X. The collected solutions were submitted to chemical analysis through flame atomic absorption spectrophotometry. It was concluded that 15% EDTA and 10% citric acid, used for 5 minutes, are effective in removing the smear layer. The apple vinegar, 10% sodium citrate, 5% acetic and maleic acids and sodium hypochlorite were not effective in removing the smear layer from root canal. 15% EDTA presented a higher concentration of calcium ions in solution, followed by 10% citric acid. Intermediary results were observed by apple vinegar, 5% acetic and maleic acids, and the inferior concentration of calcium ions was obtained with the 10% sodium citrate.

The majority of water soluble vitamin and organic acid food additives are distributed in their crystalline forms. However, when they are combined with water and other food ingredients and then exposed to a variety of unit operations, there is potential to solidify these initially crystalline ingredients in the amorphous state. Amorphous solids are generally less chemically and physically stable than their crystalline counterparts. To ensure nutrient delivery to the consumer and fulfill labeling laws, deterioration of nutrients due to unintentional amorphization is undesirable. Additionally, the potential for recrystallization of an amorphous ingredient may alter texture and redistribute water. Hence, solid state form is a critical factor dictating the stability of food formulations. Building on earlier work from my M.S. degree that demonstrated thiamine chloride hydrochloride could solidify in the amorphous state in the presence of a variety of polymers (Arioglu-Tuncil et al., 2017), a major goal of this study was to develop a comprehensive understanding of the physical and chemical stability of amorphous forms of two thiamine salts, thiamine chloride hydrochloride (TClHCl) and thiamine mononitrate (TMN), in comparison to their crystalline counterparts and each other. The objectives for this part of the work were to investigate amorphization/recrystallization tendencies of TMN and TClHCl in solid dispersions, as well as chemical stability of thiamine in the solid dispersions to understand the impact of vitamin form, physical state (amorphous vs. crystalline), polymer type and features (Tg, hygroscopicity, and ability for intermolecular interactions), storage conditions, proportion of vitamin to polymer,and pre-lyophilized solution pHs on thiamine degradation and the physical stability of dispersions. Thiamine degraded more when in the amorphous form compared to in the crystalline state. Additionally, polymer type and vitamin proportion influenced thiamine degradation, where thiamine degraded more when it was present in lower concentrations (in dispersions that had higher Tgs), and it was chemically more stable when a polymer with greater intermolecular interactions with the vitamin was used. As storage RH increased, variably hygroscopicities of the polymers resulted in different thiamine degradation rates. The pre-lyophilization pHs of the solutions had a significant impact on thiamine stability in the solid dispersions. Similar to thiamine salts, citric acid is a commonly used food ingredient with a high crystallization tendency. Following similar experimental designs for documenting the recrystallization tendencies of citric acid in amorphous solid dispersions to those used in the thiamine studies, hydrogen bonding and/or ionic interactions between polymer and citric acid were found to be the main stabilizing factor for delaying recrystallization, more than polymer Tg and hygroscopicity. The findings of this dissertation provide a powerful prediction approach to physically and chemically stabilize the small compounds in the complex food matrices for the production of high quality food products and ensuring nutrient delivery to target populations.<br>

Neste trabalho, os sistemas de eletrocatalisadores platina-rutênio (PtRu/C) e platina-estanho (PtSn/C) suportados em carbono de alta área superficial XC72R (Cabot) foram preparados pela redução química de precursores metálicos em solução usando o ácido cítrico como agente redutor. Os eletrocatalisadores foram preparados em diferentes valores de pH, com o objetivo de obter as condições de sínteses mais otimizadas para cada um dos sistemas preparados. O método otimizado mostrou-se eficiente na redução e ancoragem de todos os metais presente em solução, sendo possível preparar tanto catalisadores com baixos teores de segundo metal (razão atômica entre Pt:M = 90:10) quanto catalisadores com altos teores de segundo metal (Pt:M = 50:50). Os eletrocatalisadores obtidos foram caracterizados por espectroscopia de energia dispersiva de raios X, difração de raios X e microscopia eletrônica de transmissão. A atividade frente a eletro-oxidação de metanol e etanol foi avaliada através de voltametria cíclica e cronoamperometria em célula eletroquímica. Para os catalisadores com melhores desempenhos eletroquímicos foram realizados experimentos em célula a combustível unitária alimentada diretamente por metanol ou etanol. O desempenho dos eletrocatalisadores preparados foi comparado com o desempenho dos eletrocatalisadores comerciais Pt50Ru50/C e Pt75Sn25/C da linha HP (High Performance) fornecidos pela E-TEK, considerados como referência nos estudos frente a eletro-oxidação de alcoóis. Para eletro-oxidação do metanol foram obtidos eletrocatalisadores com desempenho comparável ao E-TEK e para eletro-oxidação de etanol foram obtidos eletrocalisadores com desempenho superior aos catalisadores E-TEK. / In this work, platinum ruthenium (PtRu/C) and platinum tin (PtSn/C) electrocatalysts were prepared by a chemical reduction process using citric acid as reducing agent and high surface area Vulcan Carbon XC72R (Cabot) as supports. The PtRu/C and PtSn/C catalysts were characterized by energy dispersive X-ray spectroscopy, X-ray diffraction and transmission electron microscopy. The electro-oxidation of methanol and ethanol were studied at room temperature by cyclic voltammetry and chronoamperometry. Single fuel cell experiments were carried at 90 °C and the performance of the homemade electrocatalysts prepared by citric acid method in optimized conditions were compared with commercial Pt50Ru50/C and Pt75Sn25/C E-TEK HP (High Performance) catalysts. For methanols electro-oxidation electrocatalysts with comparable E-TEKs catalysts performance were obtained and for ethanols electro-oxidation electrocatalysts with superior performance than E-TEKs electrocatalysts were obtained.

O presente estudo avaliou in vitro o efeito citotóxico das soluções de EDTA a 17% e ácido cítrico a 15% sob macrófagos peritoneais residentes, valendo-se do método MTT. Após anestesia e sacrifício de 32 camundongos Swiss machos, procedeu-se a coleta do exsudato celular pela injeção e aspiração de meio de cultura estéril na cavidade abdominal dos animais. Pelo processamento do exsudato peritoneal, obteve-se em média 95% de macrófagos. Alíquotas de 5 x 10 5 células foram plaqueadas em triplicata, de acordo com os grupos experimentais. Diluições de 0,5% de EDTA e ácido cítrico foram adicionadas ao meio de cultura num total de 1 mL. O grupo controle recebeu somente meio de cultura estéril. Verificou-se a citotoxicidade em dois momentos: períodos de curto prazo (0, 6, 12 e 24 horas) e médio prazo (1,3, 5, 7 dias). Ao final dos referidos tempos de observação, as amostras foram tratadas pelo corante MTT, obtendo-se valores de absorbância em leitora ELISA 550 nm. Todo o procedimento experimental foi repetido 2 vezes. No período de curto prazo, a análise de variância apontou diferenças significantes (p< 0,05), sendo Fc=46,07 contra Ft= 3,15, para os grupos avaliados: os Grupos EDTA (0,253 nm) e ácido cítrico (0,260 nm) foram mais citotóxicos que o Grupo controle (0,355 nm). Observações de médio prazo revelaram significância estatística (p< 0,05) entre os grupos, sendo Fc= 171,0 contra Ft= 3,15. Ambas as soluções, EDTA (0,158 nm) e ácido cítrico (0,219 nm), mostraram maior toxicidade em relação ao controle (0,310nm), porém o EDTA apresentou-se mais citotóxico que o ácido cítrico, reduzindo substancialmente a população macrofágica. Como conclusão, as soluções irrigantes testadas exerceram toxicidade aos macrófagos peritoneais em cultura, no entanto, a viabilidade tardia destas células foi menos alterada pelo ácido cítrico / The present study evaluated in vitro cytotoxic effects of 17% EDTA and 15% citric acid in murine resident macrophages using MTT assay. After anesthesia and sacrifice of thirty two Swiss male mice, it had processed the peritoneal cellular exudates by fresh culture medium injection and aspiration in peritoneal animals cavities. The peritoneal exudates were composed approximately by 95% of macrophages. 5x 10 5 cells were plated in triplicate, according experimental groups. Each 0.5% dilutions of EDTA and citric acid were applied in medium culture, resulting 1 mL volume. Fresh medium served as control. The cytotoxicity was evaluated in two moments: short term (0, 6, 12, 24 hours) and long term (1, 3, 5, 7 days). After tested periods, the samples were treated by MTT ink assay and absorbance was determined using ELISA microplate reader at 550 nm. All these procedures were repeated twice. To short term period, ANOVA showed significant differences (p< 0.05) among groups (Fc= 46.07 x Ft= 3.15). EDTA (0.253 nm) and citric acid (0.260 nm) groups exhibited more cytotoxicity than control group. Long term observations exhibited statistical differences (p< 0.05), that Fc= 171.0 x Ft= 3.15. EDTA (0.158 nm) and citric acid (0.219 nm) solutions were cytotoxic when compared to control group, thus EDTA reduced greater macrophages viability than citric acid. Based on our results it seems that final irrigants tested presented toxic effects to murine macrophages culture, but in long term evaluation citric acid was considered less irritant.

A new product, pork sticks, was developed. Optimum shelf life and safety were major concerns associated with this product. Potassium lactate (3%) or citric acid (0.5%, 0.56%, 0.60% or 0.66%) was added to pork sticks to determine their effects on microbial growth, sensory evaluation, and shelf life when stored frozen (-20°C), refrigerated (2°C), or at room temperature (22°C). Two raw materials, pork blade meat (shoulder meat; 91% lean, 9% fat) and regular 80:20 pork trim (80% lean, 20% fat) were used. The consumer panel preferred lean pork sticks made from blade meat over high-fat pork sticks made from regular 80:20 pork trim, regardless of the addition of potassium lactate (3%) or citric acid (0.5%). Pork sticks vacuum-packaged and held at 2°C or -20°C did not develop bacterial spoilage during six months storage. However, bacterial spoilage and oxidative rancidity occurred in the unpackaged control samples held at 22°C for one month. Incorporation of potassium lactate (3%) or citric acid (0.5%) decreased the color uniformity and red color intensity and increased the brown color intensity of the pork sticks made from blade meat. Vacuum-packaged pork sticks with added citric acid (0.56%, 0.60% and 0.66%) stored at 22°C did not develop bacterial spoilage, but discoloration occurred after one month storage.

Eine der für die biotechnologische Nutzung interessanten Eigenschaften der Hefe Yarrowia (Y.) lipolytica ist ihr Vermögen, unter bestimmten Kultivierungsbedingungen große Mengen an organischen Säuren, darunter auch Citronensäure (CS), ins extrazelluläre Medium zu sekretieren. Aufgrund ihrer Apathogenität, ihres breiten Substratspektrums und ihrer guten molekulargenetischen und verfahrenstechnischen Handhabbarkeit, stellt sie einen idealen Mikroorganismus zur biotechnologischen Gewinnung von Citronensäure dar. Bei der durch eine Stickstofflimitation ausgelösten Überproduktion von CS mit Y. lipolytica kommt es parallel auch zur Ausscheidung von Isocitronensäure (ICS), deren Anteil am Gesamtsäureprodukt in Abhängigkeit von der C-Quelle in Wildtypstämmen zwischen 10 % (Glucose, Saccharose, Glycerol) und 40-55 % (Pflanzenöle, Alkan) liegt. In der Literatur beschriebene Mutantenstämme von Y. lipolytica besitzen ein von Wildtypstämmen abweichendes Produktmuster und können sowohl weniger (2-5 % auf Glucose, 5-10 % Alkan und Pflanzenöl) als auch mehr ICS (15-35 % Glu¬cose, 65-75 % Alkan, Ethanol bzw. Pflanzenöl) sekretieren. Die gezielte Überexpression des für die Isocitratlyase codierenden Gens ICL1 durch die Erhöhung der Kopiezahl führte zu einer drastischen Erhöhung der Enzymaktivität in den entsprechenden ICL1 multicopy Transformanden (10-15fach gegenüber Wildtyp) aufgrund des Gen-Dosis-Effektes. Auf den getesteten hydrophilen C-Quellen Glucose, Glycerol und Saccharose verringerte sich der ICS-Anteil von durchschnittlich 10-12 % auf 3-5 %, auf den hydrophoben C-Quellen Hexadecan und Sonnenblumenöl sogar von durchschnittlich 40-55 % auf Werte um 5-10 %. Im Ergebnis dieser Untersuchungen entstand ein Patent (DE10333144A1), welches ein Verfahren zur Gewinnung von CS mit einer genetisch veränderten Hefe Y. lipolytica beschreibt. Die Zerstörung des Leserahmens des ICL1 Gens in Mutantenstämmen bewirkte das Ausbleiben der Synthese einer funktionell aktiven Isocitratlyase, was den Verlust der Fähigkeit zur Verwertung gluconeogenetischer C-Quellen wie Ethanol, Alkan und Pflanzenölen zur Folge hatte. Auf Glucose bzw. Glycerol zeigten diese Mutantenstämme im Vergleich zum Wildtypstamm jedoch nur eine geringe Erhöhung des ICS-Anteils um durchschnittlich 2-5 Prozentpunkte. Die Zerstörung des Leserahmens des IDP2 Gens, codierend für die NADP-abhängigen Isocitratdehydrogenase, führte zur Glutamat-Auxotrophie des entsprechenden Mutantenstammes auf allen getesteten C-Quellen. In der Produktbildung zeigte diese Mutante im Vergleich zum Wildtypstamm eine Verringerung des ICS-Anteils um durchschnittlich 2-4 Prozentpunkte. Es konnte gezeigt werden, dass Saccharose ein geeignetes Substrat zur Gewinnung von CS mit rekombinanten Stämmen von Y. lipolytica darstellt, die das für die Invertase codierende SUC2 Gens aus Saccharomyces cerevisiae exprimieren. Natürlicherweise kann Y. lipolytica diesen Zucker aufgrund des Fehlens des Enzyms Invertase nicht verwerten. Im Schüttelkolben wurden aus 100 g/l Saccharose unter nicht optimierten Bedingungen bereits 56 g/l CS+ICS gewonnen. Nach der Optimierung durch die Reduktion des für die Invertaseexpression durch pXPR2 notwendigen Peptonanteils von 1,7 auf 0,4 g/l erhöhte sich die Produktkonzentration auf 77 g/l. Die Übertragung des Produktionsprozesses in den Bioreaktor hatte die Verdopplung der Produktbildungsraten (RZA von 0,4 auf 0,85 g/l*h, r von 46 auf 89 mg/g*h) zur Folge, bedingt durch die Aufhebung der Sauerstofflimitation. Die Steigerung der Invertaseaktivität, die sich unter Bioreaktorbedingungen als ein Limi¬tationsfaktor her¬ausstellte, konnte durch die Anhebung des pH-Wertes von 5,0 auf 6,0 bzw. 6,8 er¬reicht werden. Dadurch konnten die Produktbildungsrate RZA um bis zu 80 % von 0,42 auf 0,76 g/l*h, die biomassespezifische Produktbildungsge¬schwin¬digkeit r um bis zu 70 % von 0,06 auf 0,1 g/g*h und die Ausbeute um bis zu 64 % von 0,5 auf 0,82 g/g gesteigert werden. Einen weiteren Limitationsfaktor für den CS-Bildungsprozess aus Saccharose stellt bei ausreichender Invertaseexpression offenbar die Aufnahme von Glucose und Fructose dar. Die Hefe Y. lipolytica zeigte höchste Produktbildungsraten aus Pflanzenölen, wie Sonnenblumen- oder Rapsöl, als nachwachsende Rohstoffe. Um zu prüfen, ob die Produktivität der CS-Bildung aus Pflanzenölen mit Y. lipolytica gesteigert werden kann, sollte die Triglyceridverwertung durch die Erhöhung der extrazellulären Lipaseaktivität verbessert werden. Dazu wurden zum einen Insertionsmutantenstämme, die auf eine erhöhte extrazelluläre Lipaseaktivität im Plattentest hin selektiert wurden, charakterisiert. Zum anderen wurde das für die extrazelluläre Lipase codierende LIP2 Gen in Y. lipolytica überexprimiert. Die erhaltenen LIP2 multicopy Transformanden zeigten eine bis zu 400fach erhöhte Lipaseaktivität im Vergleich zum Wildtypstamm (von 400 U/l auf bis zu 150000 U/l). Eine Verbesserung der Triglyceridverwertung aufgrund der Erhöhung der extrazellulären Lipaseaktivität in den untersuchten Insertionsmutanten und LIP2 multicopy Transformanden wurde nicht festgestellt. Die erhaltenen Daten für die Produktbildungsrate RZA (0,9-1,1 g/l*h), die biomassespezifische Produktbildungsgeschwindigkeit r (0,08-0,14 g/g*h) und die Ausbeuten (1,3-1,5 g/g) waren innerhalb der untersuchten Stämme vergleichbar und ließen keine verbesserte Produktbildung erkennen. Der geschwindigkeitsbestimmende Schritt liegt offenbar nicht bei der Hydrolyse der Triglyceride durch Lipasen, sondern bei der Aufnahme und dem Transport der Fettsäuren und/oder deren Katabolismus.

The thesis is a summary and discussion of eight papers. During the last decades, precipitation has become increasingly acidic due to the extensive use of fossil fuels. In areas of poorly buffered bedrocks, e.g. Scandinavia, northeastern United States, this phenomenon has resulted in elevated amounts of Al(III) being leached into streams and lakes. Recent findings reveal that these elevated Al-concentrations could cause fish death and decreasing forest production. In the present thesis, the importance of taking naturally occurring substances into consideration when discussing Al(III) in natural waters, is emphasized. On the basis of a chemical characterization of relevant ligand classes in a natural water, the complex formation between Al^+, hydroxide ions and the inorganic ligand carbonic acid, the low-molecular weight organic ligand citric acid and the high-molecular weight model substances gallic acid, 1,2-dihydroxynaphtha-lene-4-sulfonate, 1,2-naphthoquinone-4-sulfonate, pyrocatechol and salicylic acid were investigated. The investigations were performed as series of Potentiometrie titrations and data were processed by means of the least-squares computer program LETAGROPVRID using a technique called pqr-analysis, permitting an unbiased search for complex model (and corresponding equilibrium constants) to be made. In most systems studied, the complexation at high ligand excesses can be described by a series of mononuclear complexes AIL-AIL^. Tentatively, the whole series consists of octahedrally coordinated (water and ligand oxygens) AI(III). At lower ligand excesses, the significance and in some cases even predominance of ternary mono- and polynuclear hydroxo complexes is demonstrated. In two of the systems, binary aluminium hydroxo species are evaluated. The potential importance of the substances with respect to Al-com-plexation in natural waters are indicated in a number of model calculations. The solubility of the clay mineral kaolinite is calculated as a function of -lg[H+] and ligand concentration. It is shown that citric acid, gallic acid, 1,2-dihydroxynaphthalene-4-sulfonate, pyrocatechol and salicylic acid contribute quite significant to the total solubilities, even at very low concentrations. As a complement and background to the equilibrium studies, the corrosion rate for one of the naturally occurring Al-bearing minerals, corundum, is reported. In this investigation, performed with a leach-ant solution of ground-water composition, an experimental technique was employed which made it possible to divide the corrosion into chemical and mechanical losses. / <p>Diss. (sammanfattning) Umeå : Umeå universitet, 1983</p> / digitalisering@umu

Made available in DSpace on 2014-06-11T19:32:59Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-03-19Bitstream added on 2014-06-13T19:03:50Z : No. of bitstreams: 1 dantas_aar_dr_arafo.pdf: 3751383 bytes, checksum: 3e1b8a2e3a4274e6debc8eb99cd9a12e (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A remoção da smear layer e a exposição da matriz colágena da dentina de superfícies radiculares desprovidas de sua inserção conjuntiva tem o potencial de auxiliar o tratamento e/ou a regeneração periodontal. Diferentes substâncias têm sido empregadas para remover esta camada e expor fibras colágenas da superfície dental. A adesão de elementos sangüíneos a superfícies radiculares desmineralizadas e a estabilização do colágeno pelas fibras colágenas são de extrema importância no sucesso da cirurgia periodontal. O objetivo deste estudo foi avaliar os diferentes padrões de adsorção e adesão de plasma rico em plaquetas (PRP) e de PRP + células sangüíneas a superfícies radiculares quimicamente condicionadas. Oitenta dentes foram raspados, eqüitativamente divididos em 5 grupos: irrigação com soro fisiológico (controle), aplicação de solução de ácido cítrico a 25%, gel de EDTA a 24%, solução de cloridrato de tetraciclina a 50mg/mL e solução de citrato de sódio a 30%. Metade das superfícies condicionadas foi exposta ao PRP e a outra metade ao PRP e sangue fresco para avaliação com microscopia eletrônica de varredura. Não houve diferenças estatisticamente significantes entre os grupos quando aplicou-se o PRP seguido de sangue. O EDTA e o ácido cítrico mostraram-se mais efetivos na remoção de smear layer, porém o ácido cítrico foi o único agente que apresentou adesão de PRP nas superfícies radiculares. Dessa forma, o emprego do PRP sobre a superfície radicular pareceu favorecer a adsorção e adesão de células sangüíneas e a estabilização da rede de fibrina. / Smear layer removal and collagen fibers exposure may improve periodontal treatment and regeneration. Different substances have been used to remove it and to expose collagen fibers from tooth surface. Blood elements adhesion to demineralized roots and clot stabilization by collagen fibers are extremely important for the success of periodontal surgery. The aim of this study was to evaluate the different patterns of platelet – rich plasma (PRP) and PRP + blood cells adsorption and adhesion to root surfaces chemically conditioned. Eighty teeth were planed and equitably divided into five groups: irrigation with saline solution (control), application of a 25% citric acid solution, 24% EDTA gel, 50mg/mL tetracycline hydrochloride and 30% sodium citrate solution. Half of the conditioned surface was exposed to PRP and another half to the PRP and fresh blood and prepared for scanning electron microscopy. Planed root surfaces and conditioned with EDTA and citric acid were more effective on smear layer removal, but citric acid was the only agent that showed blood cells adhesion to root surface. This way, PRP employments on root surface probably improve blood element adsorption and adhesion to root surface and fibrin network stabilization.