• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 30
  • 8
  • 4
  • 4
  • 2
  • 1
  • 1
  • Tagged with
  • 59
  • 47
  • 7
  • 7
  • 7
  • 6
  • 6
  • 6
  • 5
  • 5
  • 5
  • 5
  • 4
  • 4
  • 4
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Study on succinic acid extraction by liquid membranes and aqueous two-phase systems containing ionic liquids / イオン液体を含む液膜および水性2相法によるコハク酸の抽出に関する研究 / イオン エキタイ オ フクム エキマク オヨビ スイセイ 2ソウホウ ニヨル コハクサン ノ チュウシュツ ニカンスル ケンキュウ

プラティヴィ アウリア インダ, Aulia Indah Pratiwi 22 March 2015 (has links)
近年発酵生産が注目されているコハク酸の抽出分離法についてイオン液体を含む液膜法及び水性2相抽出法を用いて研究した.イオン液体を含む含浸型液膜により,受容相に塩酸水溶液を用いることでコハク酸の上り坂輸送を達成できた.次にイオン液体を含む高分子溶媒膜によるコハク酸の透過を検討した.最適な条件は含浸液膜と異なり,透過にはコハク酸の各化学種が関与していた.最後に水溶性有機溶媒やイオン液体を用いた水性2相抽出法によるコハク酸の抽出を行った.塩および糖を相分離剤とすることで,発酵液で想定されるコハク酸の80%以上の抽出が達成できた. / Succinic acid is widely used in many industrial sectors; pharmacy, textile, food, etc. The bio-production of succinic acid from renewable resource was desired because the petrochemical production of succinic acid became costly. In this study, the extraction and separation techniques of succinic acid by liquid membranes (LMs) and aqueous two-phase system (ATPS) containing ionic liquids (ILs) were exploited. The permeation mechanisms and optical conditions were elucidated. / 博士(工学) / Doctor of Philosophy in Engineering / 同志社大学 / Doshisha University
32

Multi-Faceted Dietary Approaches for Lowering Postprandial Glycemia: Applications to Medical Foods

Heacock, Patricia Marie 31 March 2003 (has links)
No description available.
33

Formation and physicochemical properties of crystalline and amorphous salts with different stoichiometries formed between ciprofloxacin and succinic acid

Paluch, Krzysztof J., McCabe, T., Müller-Bunz, B., Corrigan, O.I., Healy, A.M., Tajber, L. 15 August 2013 (has links)
Yes / Multi-ionizable compounds, such as dicarboxylic acids, offer the possibility of forming salts of drugs with multiple stoichiometries. Attempts to crystallize ciprofloxacin, a poorly water-soluble, amphoteric molecule with succinic acid (S) resulted in isolation of ciprofloxacin hemisuccinate (1:1) trihydrate (CHS-I) and ciprofloxacin succinate (2:1) tetrahydrate (CS-I). Anhydrous ciprofloxacin hemisuccinate (CHS-II) and anhydrous ciprofloxacin succinate (CS-II) were also obtained. It was also possible to obtain stoichiometrically equivalent amorphous salt forms, CHS-III and CS-III, by spray drying and milling, respectively, of the drug and acid. Anhydrous CHS and CS had melting points at ∼215 and ∼228 °C, while the glass transition temperatures of CHS-III and CS-III were ∼101 and ∼79 °C, respectively. Dynamic solubility studies revealed the metastable nature of CS-I in aqueous media, resulting in a transformation of CS-I to a mix of CHS-I and ciprofloxacin 1:3.7 hydrate, consistent with the phase diagram. CS-III was observed to dissolve noncongruently leading to high and sustainable drug solution concentrations in water at 25 and 37 °C, with the ciprofloxacin concentration of 58.8 ± 1.18 mg/mL after 1 h of the experiment at 37 °C. This work shows that crystalline salts with multiple stoichiometries and amorphous salts have diverse pharmaceutically relevant properties, including molecular, solid state, and solubility characteristics. / Solid State Pharmaceutical Cluster (SSPC), supported by Science Foundation Ireland under grant number 07/SRC/ B1158.
34

Succinic acid production by wine yeasts

De Klerk, Jean-Louis 03 1900 (has links)
Thesis (MScAgric (Viticulture and Oenology))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: One of the most striking qualities of wine is its tart, sour taste. The sensory perception of sourness is mainly attributed to the presence of hydrogen ions (protons) at high concentrations. Large amounts of weak carboxylic acids (organic acids) are the main sources of these ions within wine. Once wine enters a person's mouth, the dissociable protons of the weak organic acids within wine are partially neutralized or, in other words, titrated by the saliva secreted inside one's mouth. This explains why the duration and intensity of a wine's sourness is related to its titratable acidity content. The sour taste of wine is usually considered refreshing and it helps balance wine flavour. In fact, wines become watery when its titratable acidity content is too low. After alcoholic fermentation, the titratable acidity of wine will usually be less than that of the grape juice from which was made due to ethanol-induced precipitation of potassium bitartrate crystals and partial consumption of malic acid by fermenting wine yeasts. Occasionally however, increases in titratable acidity are observed during alcoholic fermentation. If wine is produced from grape juice with optimum levels of titratable acidity, unforeseen increases in titratable acidity during alcoholic fermentation can be detrimental to the quality of the final product. Although the net production of malic acid by wine yeasts contributes to increases in titratable acidity seen during grape juice fermentations, the production of succinic acid is regarded as the primary contributor. In fact, succinic acid accounts for approximately 90% of the non-volatile acids produced during fermentation of grape juice. Between 0.5 and 1.5 g/L succinic acid is normally found in wine, but higher concentrations thereof (up to 3.0 g/L) have been detected within certain red wines. Acidity adjustments should preferably be carried out before the onset of alcoholic fermentation to allow better integration of the added compound(s) and to ensure that conditions during fermentation favour the quality and microbial stability of the final product. In doing so unfortunately, winemakers run the risk of ending up with wines that may taste too sour if they are unable to accurately predict and take into consideration the amount of succinic acid produced during alcoholic fermentation. Knowledge with regard to the factors involved in succinic acid's production by fermenting wine yeasts is therefore required in order to manage the titratable acidity of wines more accurately. Ever since Louis Pasteur first noticed succinic acid amongst the by-products of alcoholic fermentation, attempts have been made to determine the metabolic pathways and factors involved in its production by fermenting wine yeasts. Up until now however, it remains unclear why wines sometimes end up with exceptionally high levels of succinic acid. For these reasons it was decided to investigate the possible causes of very high succinic acid concentrations within wine. Due to complexity of grape juice's chemical composition and the problems associated with sterilizing grape juice, fermentation experiments were conducted within a chemically defined grape juice-like medium. Succinic acid production by nine different industrial wine yeast strains was studied under various conditions with regard to the nutrient status of the synthetic grape juice, temperature and availability of molecular oxygen during alcoholic fermentation. The amount of succinic acid produced during alcoholic fermentation was found to depend on the yeast strain, fermentation temperature and chemical composition of the synthetic grape juice. Out of the nine commercial yeast strains selected for this study, strain WE372 produced the largest amount of succinic acid in synthetic grape juice at 28°C. Strain WE372 produced significantly smaller amounts of acetic acid than the other yeast strains of this study and very little acetic acid at 28°C, which indicated that strain WE372 may have less acetaldehyde dehydroganase activity than the other yeast strains of this study under the conditions tested. The effect this has on NAD: NADH balance is the probable cause for its ability to form more glycerol, succinic and malic acid than the other strains. Results from our study show that succinic acid production is influenced primarily by the metabolizable fraction of YAN, which we termed metabolically available nitrogen (MAN). Succinic acid production by fermenting yeasts will be favoured by moderate to high fermentation temperatures (20°C to 28°C) in grape juice with a nicotinic acid and/ or nicotinamide deficiency, high sugar content (200 g/L to 240 g/L), moderate amounts of metabolically available nitrogen (300 ± 50 mg/L MAN), the presence of flavonoids and large supplies of unsaturated long-chain fatty acids. Even higher concentrations of succinic acid were produced when oxygen was made available to fermenting yeasts by aerating the fermenting grape juice. Fermentation temperatures below 18°C, too much metabolizable nitrogen (> 450 mg/L MAN), very high concentrations of fermentable sugar (> 240 g/L), lipid deficiencies and a lack of pantothenic acid, thiamine, biotin or pyridoxine will decrease the amount of succinic acid produced fermenting yeasts. / No Afrikaans summary available.
35

Potential study of chemical and pharmacological of secundary metabolites of coast cearense fungi: Aspergillus sp. / Estudo do potencial quÃmico e farmacolÃgico de metabÃlitos secundÃrios de fungos da costa cearense: Aspergillus sp.

JoÃo Evangelista de Ãvila dos Santos 25 September 2015 (has links)
CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / This study aimed to the chemical and pharmacological research of biodiversity of marine fungi associated with sediment from the coastline of northeastern Brazil, especially the state of CearÃ. From the collection of marine sediments at the beach Pecem - SÃo GonÃalo do Amarante-CE, were cultivated various fungi, of which the strain identified as Aspergillus sp. (BRF 087), showed a preliminary cytotoxic activity. The methodology has been directed in finding secondary metabolites with cytotoxic activity using a kinetic fungus study was grown in four different media, BD (potato dextrose), BDL (potato dextrose and yeast), MPD (malt, peptone and dextrose ) and MntPL (mannitol, peptone and yeast) and in different culture periods (7, 14, 21, 28 days). This procedure resulted in the isolation of nine diketopiperazines two tetrapeptides cycle, 3 derivatives of succinic acid and p-hydroxyphenylacetic acid, characterized as cyclo (L-Pro-L-Leu) (A-1), cyclo (L-Pro-L -Phe) (A-2), cyclo (4-OH-Pro-Leu) (A-3), cyclo (4-OH-Pro-Phe) (A-4), cyclo (L-Pro-L-tyr ) (A-5), cyclo (L-Leu-L-Val) (A-6), cyclo (L-Phe-L-Val) (A-7), cyclo (L-Phe-L-Leu) (A-8), cyclo (L-Leu-L-Ile) (A-9), cyclo (L-Ile-L-Pro-L-Leu-L-Pro) (A-10), cyclo (Leu-Ile Leu-Phe) (A-11), 2-metilenosuccinic acid (A-12), 3-Methyl-2-metilenosuccinic (A-13), 4-metoxy-2-methylidene-4-oxobutanoic acid (A-14) and p-hydroxyphenylacetic acid (A-15). The isolation of secondary metabolites was conducted by using usual chromatographic techniques, including chromatography on reverse phase C18 column and high-performance liquid chromatography (HPLC). For structural characterization of the compounds were used customary spectrometric techniques like IR, mass spectrometry and nuclear magnetic resonance (NMR), one and two dimensional, and compared with literature data. / O presente trabalho teve como objetivo principal a investigaÃÃo quÃmico-farmacolÃgica da biodiversidade dos fungos marinhos associados a sedimentos da costa litorÃnea do Nordeste do Brasil, e em especial do estado do CearÃ. A partir da coleta de sedimentos marinhos na praia do PecÃm - SÃo GonÃalo do Amarante-CE, foram cultivados vÃrios fungos, dos quais a cepa identificada como Aspergillus sp. (BRF 087), mostrou uma atividade citotÃxica preliminar. A metodologia empregada foi direcionada na busca de metabÃlitos secundÃrios com atividade citotÃxica, atravÃs de um estudo cinÃtico do fungo que foi cultivado em quatro meios diferentes, BD (batata dextrose), BDL (batata dextrose e levedura), MPD (malte, peptona e dextrose) e MntPL (manitol, peptona e levedura) e em diferentes perÃodos de cultivo (7, 14, 21, 28 dias). Este procedimento resultou no isolamento de nove dicetopiperazinas, dois ciclo tetrapeptÃdeos, 3 derivados do Ãcido succinio e o Ãcido p-hidroxifenilacÃtico, caracterizados como ciclo (L-Pro-L-Leu) (A-1), ciclo (L-Pro-L-Fen) (A-2),ciclo (4-OH-Pro-Leu) (A-3), ciclo (4-OH-Pro-Fen) (A-4), ciclo (L-Pro-L-Tyr) (A-5), ciclo (L-Leu-L-Val) (A-6), ciclo (L-Fen-L-Val) (A-7), ciclo (L-Fen-L-Leu) (A-8), ciclo (L-Leu-L-Ile) (A-9), ciclo (L-Ile-L-Pro-L-Leu-L-Pro) (A-10), ciclo (Leu-Ile-Leu-Fen) (A-11), Ãcido 2-metilenosuccinio (A-12), Ãcido 3-metil-2-metilenosuccinio (A-13), Ãcido 4-metoxi-2-metileno-4-oxobutanÃico (A-14) e o Ãcido p-hidroxifenilacÃtico (A-15). O isolamento dos metabÃlitos secundÃrios foi realizado atravÃs do uso de tÃcnicas cromatogrÃficas usuais, incluindo cromatografia em coluna de fase reversa C18 e cromatografia lÃquida de alta eficiÃncia (CLAE). Para a caracterizaÃÃo estrutural dos compostos foram utilizadas tÃcnicas espectromÃtricas usuais como infravermelho, espectrometria de massa e ressonÃncia magnÃtica nuclear (RMN), uni e bidimensional, alÃm de comparaÃÃo com dados da literatura.
36

Hydrogénation de l'acide succinique en phase aqueuse pour l'obtention sélective de 1,4-butanediol / Selective aqueous phase hydrogenation of succinic acid to 1,4-butanediol

Ly, Bao Khanh 16 April 2013 (has links)
Le but du projet est d’hydrogéner l’acide succinique en phase aqueuse à 160°C, sous 150 bar d’hydrogène pour obtenir sélectivement le 1,4-butanediol (BDO) en utilisant des catalyseurs x%Re-2%Pd/TiO2. Les catalyseurs monométalliques au palladium permettent d’obtenir sélectivement le produit intermédiaire : la γ-butyrolactone et très peu de BDO est obtenu. Leur activité catalytique est fonction de la dispersion de la phase métallique. L’addition de rhénium aux catalyseurs monométalliques au palladium permet de poursuivre la réaction jusqu’à l’obtention du BDO. Nous avons d’abord essayé deux méthodes d’addition ex situ de rhénium : réduction catalytique (RC) et imprégnation successive (IS). La meilleure sélectivité en BDO obtenue jusqu’à maintenant est de 90% en présence du solide 3,4%Re-2%Pd/TiO2 préparé par IS. Quelle que soit la méthode de dépôt (RC ou IS), le rhénium dans ces solides bimétalliques est réoxydé et lixivié dans la phase aqueuse sous l’atmosphère non réductrice. Malgré la lixiviation et le redépôt du rhénium sous hydrogène, le comportement des catalyseurs bimétalliques Re-Pd/TiO2 préparés ces deux méthodes reste différent. Le dépôt in situ de Re conduit à des catalyseurs bimétalliques prometteurs : SBDO = 73% avec 2% de rhénium déposé / The aim of our research project is the hydrogenation of the succinic acid in aqueous phase at 160°C, under 150 bar hydrogen to obtain selectively 1,4-butanediol (BDO) by using x%Re- 2%Pd/TiO2 catalyst. Palladium monometallic catalysts allow us to obtain selectively the intermediate product γ-butyrolactone and very little BDO. Their catalytic activity depends on the dispersion of the metallic phase. The reaction can be extended until obtaining BDO by adding the rhenium to palladium based monometallic catalysts. Firstly, we have tried two ex situ methods to add the rhenium: catalytic reduction (CR) and successive impregnation (SI). The best selectivity to BDO is 90% with the presence of 3,4%Re-2%Pd/TiO2 prepared by IS method. Moreover, for both deposition methods, the rhenium in the bimetallic catalysts is reoxidized with air and then leached into the aqueous phase. Despite leaching and redeposition of rhenium under hydrogen pressure, the behavior of bimetallic catalysts prepared by the two methods (CR and SI) is different. In situ deposition of the rhenium leads to promising bimetallic catalysts: SBDO = 73% with 2% of rhenium
37

Hydrogenation of succinic acid and carbon dioxide over molybdenum carbide catalysts / Carbures de molybdène catalyseurs supportés pour hydrogénation de l'acide succinique et du dioxyde de carbone

Abou Hamdan, Marwa 28 May 2019 (has links)
Ce travail de thèse porte sur la synthèse de carbures de molybdène sur support afin de tester leurs performances catalytiques dans des réactions d’hydrogénation. Dans ce but, la conversion d'acide succinique en phase aqueuse dans un réacteur discontinu et du dioxyde de carbone en phase gazeuse dans un réacteur à flux continu, ont été effectuées. Les catalyseurs ont été préparés par la méthode de carburation par réduction en température programmée, pendant laquelle des paramètres ont été modifiés conduisant à différents rapports molybdène/carbone. Les différents catalyseurs testés dans cette réaction étaient actifs pour la conversion de l'acide succinique en gamma-butyrolctone et, plus remarquablement, en acide butyrique, ce dernier n'était pas obtenu en quantités significatives avec des catalyseurs à base de métaux précieux. L’augmentation de la conversion d’acide succinique avec une sélectivité plus élevée en acide butyrique a été faite avec les catalyseurs contenant plus de carbone, préparés en augmentant la vitesse spatiale horaire gazeuse. Les intermédiaires ont été ensuite convertis en tétrahydrofurane, butanol, 1,4-butanediol et butane. La désactivation observée lors de recyclage du catalyseur a été principalement attribuée à une diminution de la quantité de molybdène et de carbone carbidique, démontrée par l'analyse XPS. Des essais préliminaires de ces catalyseurs dans l'hydrogénation du dioxyde de carbone ont montré qu'ils fonctionnaient principalement en tant que catalyseurs pour la réaction du gaz à l’eau inverse, et l'excès de carbone entrave l'activité catalytique d'une manière opposée à la réaction en phase aqueuse. Le support semble jouer un rôle dans la réactivité des catalyseurs, la conversion du dioxyde de carbone ainsi que la sélectivité en méthane et méthanol, qui ont augmenté dans l'ordre suivant: carbure de molybdène sur support DT51 TiO2> P25 TiO2 ˜ ZrO2 / This work focuses on the synthesis of supported molybdenum carbides and evaluating their catalytic performance in succinic acid hydrogenation reactions in aqueous phase using batch reactor and carbon dioxide hydrogenation in gas phase using continuous flow reactor. The catalysts were prepared by the temperature programmed reduction carburization method, where the parameters were modified leading to different molybdenum to carbon ratios. The different catalysts tested were active in converting succinic acid to gamma butyrolctone and more remarkably butyric acid which is not reported in significant quantities in this reaction with precious metal based catalysts. The catalysts containing more carbon contents that were prepared by increasing the gas hourly space velocity showed higher activity in converting succinic acid and higher selectivity to butyric acid. The intermediates were then converted to tetrahydrofuran, butanol, 1,4-butanediol and butane gas. The deactivation observed while recycling the catalyst was mainly attributed to a decrease in the amounts of carbidic molybdenum and carbidic carbon, as demonstrated by XPS analysis. Preliminary tests for these catalysts in carbon dioxide hydrogenation showed that they functioned mainly as reverse water gas shift catalysts, and the excess of carbon hinders the catalytic activity in an opposite manner of the reaction in aqueous phase. The support seems playing a role in the reactivity of the catalysts, carbon dioxide conversion as well as methane and methanol selectivity increased in the order: molybdenum carbide supported on DT51 TiO2 > P25 TiO2 ˜ ZrO2
38

Otimização da produção de hidrogênio e ácidos orgânicos em reator em batelada a partir de consórcio de bactérias autóctones e alóctones do bagaço de cana-de-açúcar / Optimization of hydrogen and organic acids productions with autochthonous and allochthonous bacteria from sugarcane bagasse in batch reactors

Rabelo, Camila Abreu Borges da Silva 09 February 2018 (has links)
Nessa pesquisa avaliou-se a produção fermentativa de hidrogênio e ácidos orgânicos a partir do bagaço de cana-de-açúcar (BCA) usado como substrato em reatores em batelada. Três condições de pré-tratamento (hidrotérmico, autoclave e hidrotérmico mais autoclave) do BCA e condição in natura foram avaliadas a fim de favorecer a produção de hidrogênio. Verificou-se produção molar de hidrogênio de 3,79 mmol/L, 3,47 mmol/L, 1,67 mmol/L e 1,01 mmol/L para BCA autoclavado, BCA in natura, BCA pré-tratado em sistema hidrotérmico e BCA pré-tratado em sistema hidrotérmico seguido de autoclave, respectivamente. A partir desses valores, optou-se por usar o BCA autoclavado como substrato para otimização da produção de hidrogênio e ácidos orgânicos a partir de metodologias de delineamento do composto central e superfície de resposta. Foram monitorados 10 reatores em batelada (R1 a R10), em triplicatas, com diferentes concentrações de substrato (0,8 a 9,2 g/L) e pH (de 4,6 a 7,4). A maior produção de hidrogênio (24,1 mmol/L) e 6,4 g/L de ácidos orgânicos foram obtidos em R4 (8,0 g BCA/L e pH 7,0). Os açúcares glicose, arabinose, xilose, manose e galactose foram observados ao longo do tempo de operação em todos os reatores, sendo arabinose observado em maior concentração nas condições dos reatores R3 (8,0 g BCA/L e pH 5,0) e R8 (5,0 g BCA/L e pH 7,4), respectivamente, 1.415,3 e 1.372,5 mg/L. A produção de hidrogênio foi concomitante à formação de ácidos orgânicos, principalmente butírico (de 14,6 a 33,8% em R1 e R6, respectivamente) e succínico (de 19,5 a 26,4% em R3 e R9, respectivamente). Os dois fatores analisados, concentração de substrato e pH, exerceram efeitos significativos na produção de hidrogênio, ácido butírico e succínico. A partir dos resultados obtidos com o planejamento fatorial, foi possível verificar que o valor máximo de produção de hidrogênio estimado pelo modelo foi de 23,10 mmol/L, para 7,0 g BCA/L e pH 7,2. O valor obtido no experimento de otimização (Rotm) foi de 19,84 mmol/L, com grau de precisão do modelo de 85,9% para produção de hidrogênio a partir de BCA autoclavado. Sequenciamento massivo via plataforma Illumina (Miseq) foi realizado para a identificação de bactérias do reator do ponto central, (R9, 5,0 g BCA/L e pH 6,0), do reator otimizado (Rotm, 7,0 g BCA/L e pH 7,2), de amostras do BCA autoclavado e inóculo. No inóculo foram identificadas principalmente bactérias semelhantes a Clostridium bifermentans (62,69% de abundância relativa), Bacillus coagulans (31,67%) e Enterobacter aerogenes (2,72%). No BCA foram identificadas bactérias semelhantes a C. bifermentans (31,91%), C. cellobioparum (32,29%), C. cellulolyticum (5,69%), C. sartagoforme (14,63%) e Paenibacillus spp. (11,67%). Estas bactérias não foram favorecidas sob as condições impostas em R9 (5,0 g BCA/L e pH 6,0) e Rotm (7,0 g BCA/L e pH 7,2), uma vez que a abundância relativa das bactérias nas amostras dos reatores foram completamente diferentes. Em R9, bactérias semelhantes a Lactobacillus paracasei e Escherichia hermannii foram as principais identificas com 37,50 e 34,32% de abundância relativa, respectivamente. Em Rotm, as principais bactérias identificadas foram semelhantes a Bacteroides sp. e Enterobacter aerogenes, com 37,35 e 27,72% de abundância relativa, respectivamente. Assim, as populações bacterianas, bem como a produção de metabólitos, foram alteradas em função das condições impostas; ou seja, concentração de BCA, pH em reatores em batelada com BCA autoclavado como substrato. / This study evaluated the hydrogen and organic acids fermentative productions from sugarcane bagasse (SCB) as substrate in batch reactors. Three pre-treatment conditions (hydrothermal, autoclave and hydrothermal plus autoclave) of BCA and the in natura condition were evaluated in order to favor the hydrogen production. Hydrogen molar productions of 3.79 mmol/L, 3.47 mmol/L, 1.67 mmol/L and 1.01 mmol/L was found for SCB pretreated in autoclave, BCA in natura, SCB pretreated in hydrothermal system and SCB pretreated in hydrothermal system followed by autoclaving, respectively. From these values, it was decided to use autoclaved BCA as a substrate for optimization of hydrogen and organic acids productions from the design methodologies of the central compound and response surface. Ten batch reactors (R1 to R10) were monitored in triplicates with different substrate concentrations (0.8 to 9.2 g/L) and pH (4.6 to 7.4). The highest production of hydrogen (24.06 mmol/L) and 6.42 g/L of organic acids were obtained in R4 (8.0 g BCA/L and pH 7.0). Glucose, arabinose, xylose, mannose and galactose were produced and consumed throughout the operating time of all reactors, and arabinose was observed at higher concentration, 1,415.26 and 1,372.45 mg/L in R3 (8.0 g BCA/L and pH 5.0) and R8 (5.0 g BCA/L and pH 7.4), respectively. The production of hydrogen was concomitant to the formation of organic acids, mainly butyric (from 14.6 to 33.8% in R1 and R6, respectively) and succinic (from 19.5 to 26.4% in R3 and R9, respectively). The two factors analyzed, substrate concentration and pH, had significant effects on the production of hydrogen, butyric acid and succinic acid. From the results obtained with the factorial design, it was possible to verify that the maximum value of hydrogen production estimated by the model was 23.10 mmol/L, to 7.0 g BCA L and pH 7.2. The value obtained in the optimization experiment (Rotm) was 19.84 mmol/L, with an accuracy of 85.9% for hydrogen production from autoclaved BCA. Sequencing by the Illumina platform (Miseq) was performed for the identification of bacteria from the central point reactor (R9, 5.0 g BCA/L and pH 6.0), optimized reactor (Rotm, 7.0 g BCA/L and pH 7.2), autoclaved BCA and inoculum samples. In the inoculum were identified mainly bacteria similar to Clostridium bifermentans (62,69% of relative abundance), Bacillus coagulans (31,67%) and Enterobacter aerogenes (2,72%). Bacteria similar to C. bifermentans (31.91%), C. cellobioparum (32.29%), C. cellulolyticum (5.69%), C. sartagoforme (14.63%) and Paenibacillus spp. (11.67%). These bacteria were not favored under the conditions imposed on R9 (5.0 g BCA/L and pH 6.0) and Rotm (7.0 g BCA/L and pH 7.2), since the relative abundance of the bacteria in the reactor samples were completely different. In R9, bacteria similar to Lactobacillus paracasei and Escherichia hermannii were the main identified with 37.50 and 34.32% of relative abundance, respectively. In Rotm, the main bacteria identified were similar to Bacteroides sp. and Enterobacter aerogenes, with 37.35 and 27.72% relative abundance, respectively. Thus, bacterial populations, as well as the production of metabolites, were altered as a function of the imposed conditions; ie, BCA concentration, pH in batch reactors with autoclaved BCA as substrate.
39

Strategies for building polymers from renewable sources : Using prepolymers from steam treatment of wood and monomers from fermentation of agricultural products

Söderqvist Lindblad, Margaretha January 2003 (has links)
A strategic research area today is development of polymericproducts made from renewable sources. The ways of utilizingrenewable sources studied in this thesis are using 1)prepolymers obtained by steam treatment of wood and 2) monomersobtainable by fermentation of agricultural products. Novel hemicellulose-based hydrogels were prepared by usingprepolymers obtained from steam treatment of spruce.Hemicellulose was first modified with well-defined amounts ofmethacrylic functions. Hydrogels were then prepared by radicalpolymerization with 2-hydroxyethyl methacrylate orpoly(ethylene glycol) dimethacrylate to form hydrogels. Theradical polymerization reaction was carried out in water usinga redox initiator system. The hydrogels were in generalelastic, soft and easily swollen in water. Frequency sweeptests indicated that the hydrogel system displayed prevailingsolid-like behavior. Comparison of the hemicellulose-basedhydrogels with pure poly(2-hydroxyethyl methacrylate)-basedhydrogels showed that it was possible to preparehemicellulose-based hydrogels with properties similar to thoseof pure poly(2-hydroxyethyl methacrylate)-based hydrogels. Polyester-based materials were prepared by using themonomers 1,3- propanediol and succinic acid obtainable byfermentation. α,ω-Dihydroxyterminatedoligomeric polyesters produced by the thermal polycondensationof 1,3-propanediol and succinic acid were chain-extended toobtain sufficiently high molecular weight. Depending on thechain-extension technology adopted, poly(ester carbonate)s orpoly(ester urethane)s were obtained. In the case of poly(estercarbonate)s, the chain-extended products ofα,ω-dihydroxyterminated oligomeric copolyesters werealso produced using 1,3-propanediol/1,4-cyclohexanedimethanol/succinic acid mixtures toimprove thermal and mechanical properties. Segmented poly(esterether carbonate)s fromα,ω-dihydroxyterminated oligo(propylenesuccinate)s and poly(ethylene glycol) were also synthesized toincrease the hydrophilicity. Molecular weights and polydispersity were analyzed by SECfor all materials. Their structures were also identified by NMRspectroscopy (1H NMR and 13C NMR). All characterizations werein agreement with the proposed structures. Thermal parameterswere characterized by DSC. Tensile testing anddynamic-mechanical tests were performed and in additionpreliminary processing trials were carried out in some cases.The results demonstrate the feasibility of using monomersderived from renewable sources to build up new polymericstructures endowed with a variety of physical and mechanicalproperties.
40

Synthesis And Electrochromic Properties Of Conducting Polymers Of Succinic Acid Bis-(2-thiophen-3-yl-ethyl)ester And Their Use In Electrochromic Devices

Sacan, Lale 01 June 2006 (has links) (PDF)
ABSTRACT SYNTHESIS AND ELECTROCHROMIC PROPERTIES OF CONDUCTING POLYMERS OF SUCCINIC ACID BIS-(2-THIOPHEN-3-YL-ETHYL) ESTER AND THEIR USE IN ELECTROCHROMIC DEVICES Sa&ccedil / an, Lale M.Sc., Department of Chemistry Supervisor: Prof. Dr. Levent Toppare June 2006, 59 pages A new monomer / succinic acid bis-(2-thiophen-3-yl-ethyl)ester (SATE) was synthesized through the esterification reaction of 2-thiophen-3-yl-ethanol and succinyl chloride. The chemical structure of monomer was characterized via Nuclear Magnetic Resonance Spectroscopy (NMR) and Fourier Transform Infrared Spectroscopy (FTIR). Electrochemical behaviors of SATE alone and SATE in the presence of thiophene were studied by cyclic voltammetry (CV). The synthesis of homopolymer and copolymer were achieved via constant potential electrolysis. Both homopolymer (PSATE) and copolymer [P(SATE-co-Th)] were characterized by various techniques including cyclic voltammetry, FTIR, Scanning Electron Microscopy (SEM), Differential Scanning Calorimetry (DSC), Thermal Gravimetry Analysis (TGA) and UV-VIS Spectrophotometer. Conductivities of samples were measured by four probe technique. The electrochromic properties of the polymers were investigated via spectroelectrochemistry, colorimetry and switching studies. In addition, dual type electrochromic devices (ECDs) composed of PSATE, P(SATE-co-Th) and poly(3,4-ethylenedioxythiophene) (PEDOT) were constructed and evaluated. Spectroelectrochemistry, switching ability and stability of the devices were investigated by UV-Vis Spectrophotometer and Cyclic Voltammetry. They have shown to possess good switching times, reasonable contrasts, high stabilities and optical memories.

Page generated in 0.0521 seconds