Hidrolisados hemicelulósicos como o resultante do processamento do bagaço de cana-de-açúcar para obtenção do etanol celulósico, constituem uma fonte rica em açúcares, em particular xilose. Considerando o potencial destes hidrolisados para utilização por micro-organismos fermentadores de pentoses e a disponibilidade de leveduras xilanolíticas isoladas da Antártica, a presente pesquisa tem como objetivo avaliar o cultivo destas leveduras no hidrolisado hemicelulósico de bagaço de cana-de-açúcar com vistas à obtenção de bioprodutos. Os experimentos foram realizados empregando-se 16 leveduras xilanolíticas isoladas de diferentes fontes. Inicialmente estas foram repicadas em ágar Sabouraud e cultivadas em diferentes temperaturas, selecionando-se para o cultivo em hidrolisado hemicelulósico aquelas que cresceram neste meio. Os cultivos no hidrolisado foram realizados em triplicata em frascos Erlenmeyer, a 200 rpm, a 30°C em duas etapas: O primeiro ocorreu por 72 h e as leveduras que cresceram neste período foram as empregadas para avaliação do cultivo no hidrolisado e também em meio semi-definido simulando a composição em açúcares deste hidrolisado por um período de 96h. Neste caso as avaliações ocorreram a cada 24h a partir da determinação da concentração de açúcares, formação de células, xilitol e etanol, pH, concentração dos tóxicos ácido acético, hidroximetilfurfural, furfural e fenólicos. O experimento controle foi empregado utilizando-se Candida guillermondii já bastante pesquisada nas fermentações que empregam hidrolisado hemicelulósico de bagaço de cana. Foi verificado que 6 das leveduras testadas foram capazes de assimilar os açúcares presentes no hidrolisado, sendo que apenas a Cryptococcus adeliensis (L95) apresentou capacidade de produzir etanol como produto deste metabolismo, enquanto as leveduras Cryptococcus aff laurentii (L62), Candida davisiana (L101 e L107) e Cryptococcus adeliensis (L108) apresentaram indícios de atividade xilanolítica. Com relação aos compostos tóxicos presentes no hidrolisado verificou-se que em alguns cultivos ocorreu decréscimo na concentração destes e a manutenção da viabiliadade celular ao final do cultivo. Considerando o caráter inovador da presente pesquisa faz-se necessário a continuidade da investigação a fim de se estabelecer as melhores condições de cultivo destas leveduras para fins de aproveitamento biotecnológico de hidrolisados hemicelulosicos, em função do desempenho destas em relação à C. guilliermondii. / Hemicellulose hydrolysates, as the result of sugarcane bagasse processing for obtaining cellulosic ethanol, are a rich source of sugars, especially xylose. Considering the potential of these hydrolysates for the use by pentoses fermenting micro-organisms and the availability of xylanolytic yeasts isolated from Antarctica, this research aims to evaluate the cultivation of these yeasts in hemicellulose hydrolysate of sugarcane bagasse in order to obtain bioproducts. The experiments were performed by employing 16 xylanolytic yeasts isolated from different sources. Initially, they were transferred in Sabouraud agar and grown at different temperatures, and those that grew in this medium were selected for cultivation in hemicellulose hydrolysate. The cultures in the hydrolysate were performed in triplicate in Erlenmeyer flasks at 200 rpm at 30 ° C in two stages: The first one occurred for 72 h and the yeasts that grew in this period were used for the evaluation of growth in the hydrolysate and also in semi-defined medium simulating the sugar composition of this hydrolysate for 96h. In this case, the evaluations occurred every 24 hours from the determination of sugars concentration, formation of cell, xylitol and ethanol, pH, concentration of the toxics acetic acid, hydroxymethylfurfural, furfural and phenols. A control experiment was employed using Candida guillermondii which has been well investigated in fermentations employing sugarcane bagasse hemicellulose hydrolysate. It was verified that 6 of the tested yeasts were able to assimilate the sugars present in the hydrolysate, and only Cryptococcus adeliensis (L95) showed ability to produce ethanol as a product of this metabolism, while the yeasts Cryptococcus aff laurentii (L62), Candida davisiana (L101 and L107) and Cryptococcus adeliensis (L108) showed evidences of xylanolytic activity. With respect to toxic compounds present in hydrolysate, it was verified that, in some cultures, the decrease in their concentration and the maintenance of cell viability at the end of cultivation occurred. Due to the innovative nature of this research, it is necessary to continue the investigation in order to establish the best conditions for this yeasts cultivation with the purpose of biotechnological exploitation of hemicellulose hydrolysates, depending on their performance regarding C. guilliermondii.

Élargir le répertoire de composés accessibles dans le domaine des Glycosciences est d’un intérêt majeur pour la communauté des biologistes du fait que ces composés, oligosaccharides et glyco-conjugués, sont impliqués dans diverses fonctions biologiques, aussi bien au niveau structurel, qu’énergétique voire même signalétique jouant un rôle primordial dans les interactions inter- ou intracellulaires. L’assemblage, la modification ou la déconstruction de ces glyco-structures complexes est possible grâce à l’action d’enzymes, parmi lesquelles l’on retrouve les CAZymes (Carbohydrate Active enZymes). Ces enzymes font partie du répertoire de la base de données CAZy, incluant les Glycoside Hydrolases (GHs) qui représentent le groupe le plus important et ayant pour fonction biologique principale l’hydrolyse des liens glycosidiques. Cependant, un certain nombre de GHs possède aussi la capacité de catalyser des réactions de synthèse (transglycosylation) en tant qu’activité secondaire mineure, voire en tant qu’activité principale pour un nombre restreint d’entre elles, qui sont alors appelées transglycosylases. Sachant que ces deux types de comportements peuvent se retrouver au sein d’une même famille de GH (donc étroitement liés sur le plan évolutif), la découverte et la compréhension des déterminants moléculaires qui ont été développés par les GHs au cours de leur évolution pour permettre cette partition d’activité, entre hydrolyse et transglycosylation, est d’une importance capitale pour le domaine de la synthèse chimio-enzymatique et des Glycosciences de manière plus générale.Ce travail de thèse décrit une proposition de synthèse pour apporter une réponse à cette question fondamentale via une revue critique de la littérature sur le sujet. Sur le plan expérimental, a été réalisée l’évolution moléculaire d’une enzyme spécifique des pentoses, l’α-L-arabinofuranosidase de Thermobacillus xylanilyticus (TxAbf) de la famille GH51, vers les premières transarabinofuranosylases de type ‘non-Leloir’. Cette évolution itérative a été développée en utilisant un panel d’outils d’ingénierie enzymatique combinant des approches aléatoire, semi-rationnelle, de prédiction in silico suivie de recombinaison dans un processus d’évolution dirigée global. Une analyse fine des mutants générés sur le plan mécanistique en lien avec la partition hydrolyse/transglycosylation mène à des conclusions en accord avec la proposition de synthèse issue de la revue de la littérature sur le sujet. Sur un plan plus appliqué, ces nouveaux biocatalyseurs ont ensuite été mis en oeuvre dans des voies de synthèse chimio-enzymatiques pour la préparation de composés furanosylés de structure contrôlée. Le transfert d’L-arabinofuranosyles permet la génération d’arabinoxylo-oligosaccharides (AXOS) ainsi que la conception d’oligosaccharides non naturels, tel que des galactofuranoxylo-oligosaccharides ou des arabinofuranogluco-oligosaccharides. Dans son ensemble, ce travail de recherche constitue les premières étapes clés du développement de méthodes de synthèse chimio-enzymatique plus élaborées pour la conception d’arabinoxylanes artificiels. Dans le contexte actuel de transition vers une bio-économie, reposant sur des concepts tels que ceux de la bioraffinerie ou de la chimie verte, nous espérons que les outils de glycosynthèse développés au cours de ces travaux trouveront leur application dans la valorisation des pentoses issus de la biomasse. La synthèse à-façon d’arabinoxylooligo- et polysaccharides présente nombre de valorisations possibles allant de la préparation de prébiotiques à la conception de matériaux bio-inspirés en passant par la synthèse de modèles de parois végétales. / Widening the spectrum of available compounds in the field of Glycosciences is of utmost importance for the entire biology community, because carbohydrates are determinants of a myriad of life-sustaining or threatening processes. The assembly, modification or deconstruction of complex carbohydrate-based structures mainly involves the action of enzymes, among which one can identify Carbohydrate Active enZymes (CAZymes). These enzymes form part of the CAZy database repertoire and include Glycoside Hydrolases (GHs), which are the biggest group of CAZymes, whose main role is to hydrolyze glycosidic linkages. However, some GHs also display the ability to perform synthesis (transglycosylation), an activity that mostly manifests itself as a minor one alongside hydrolysis, but which is the only activity displayed by a rather select group of GHs that are often called transglycosylases. Understanding how transglycosylases have resulted from the process of evolution is both intringuing and crucial, because it holds the key to the creation of tailored glycosynthetic enzymes that will revolutionize the field of glycosciences.In this thesis, an extensive review of relevant scientific literature that treats the different aspects of GH-catalyzed transglycosylation and glycosynthesis is presented, along with experimental results of work that has been performed on a family GH-51 α-L-arabinofuranosidase, a pentose-acting enzyme from Thermobacillus xylanilyticus (TxAbf). The conclusions of the literature are presented in the form of a hypothesis, which describes the molecular basis of the hydrolysis/transglycosylation partition and thus provides a proposal on how to engineer dominant transglycosylation activity in a GH. Afterwards, using a directed evolution approach, including random mutagenesis, semi-rational approaches, in silico predictions and recombination it has been experimentally possible to create the very first ‘non-Leloir’ transarabinofuranosylases. The mechanistic analysis of the resultant TxAbf mutants notably focusing on the hydrolysis/transglycosylation partition reveals that the results obtained are consistent with the initial hypothesis that was formulated on the basis of the literature review.To demonstrate the applicative value of the experimental work performed in this study, the TxAbf mutants were used to develop a chemo-enzymatic methodology that has procured a panel of well-defined furanosylated compounds. Enzyme-catalyzed transfer of arabinofuranosyl moities can be used to generate arabinoxylo-oligosaccharides (AXOS), but the design of non-natural oligosaccharides, such as galactofuranoxylo-oligosaccharides or arabinofuranogluco-oligosaccharides is also possible. Overall, the work presented constitutes the first steps towards the development of more sophiscated methodologies that will procure the means to synthesize artificial arabinoxylans, with a first proof of concept being presented at the very end of this manuscript.In the present context of the bioeconomy transition, which relies on technologies such as biorefining and green chemistry, it is expected that the glycosynthetic tools that have been developed in this work will be useful for the conversion of pentose sugars obtained from biomass. The synthesis of tailor-made arabinoxylo-oligo- and polysaccharides may lead to a variety of potential applications including the production of prebiotics, surfactants or bio-inspired materials and, more fundamentally, the synthesis of artificial models of plant cell wall.

Les Leucémies Aigües Myéloïdes (LAM) sont des hémopathies malignes hétérogènes de mauvais pronostic qui se caractérisent par une expansion clonale de progéniteurs immatures. De nombreuses dérégulations de voies de signalisation sont retrouvées dans les cellules leucémiques et leur confèrent un avantage de prolifération et de survie. La voie de signalisation mTORC1, qui contrôle la traduction protéique, l’autophagie et plusieurs voies métaboliques, est ainsi constitutivement activée dans les cellules leucémiques. La reprogrammation métabolique notamment via « l’effet Warburg » est un phénomène bien décrit dans les cellules cancéreuses. L’augmentation de l’utilisation de la glycolyse, confère aux cellules tumorales un avantage de survie en favorisant une production rapide d’ATP et d’intermédiaires métaboliques nécessaires pour les biosynthèses de nucléotides, d’acides-aminés et de lipides. C’est donc dans ce contexte que j’ai étudié le métabolisme du glucose dans les cellules de LAM et l’implication de la voie de signalisation mTORC1 dans la dérégulation de ce métabolisme. J’ai tout d’abord identifié par une étude transcriptomique dans la lignée leucémique MOLM-14 que la signalisation mTORC1 contrôle plusieurs voies métaboliques notamment celles permettant l’utilisation du glucose. Ceci a été vérifié dans plusieurs lignées de LAM puisque l’inhibition ou la sur-activation de mTORC1 entrainent respectivement une diminution ou une augmentation de la consommation de glucose et de la production de lactate. De façon intéressante, le niveau d’activation de la voie mTORC1 détermine la sensibilité des cellules leucémiques à l’inhibition de la glycolyse. En effet, lorsque mTORC1 est activé, le blocage de la glycolyse induit de l’autophagie et l’apoptose des cellules leucémiques. A l’inverse, le blocage de mTORC1 induit une reprogrammation métabolique des cellules leucémiques qui utilisent alors principalement la phosphorylation oxydative pour produire l’ATP dont elles ont besoin. Leur survie devient alors indépendante du glucose. A l’inverse des cellules primaires de LAM, les cellules hématopoïétiques immatures normales CD34+ sont moins sensibles au blocage de la glycolyse. Le ciblage du métabolisme du glucose pourrait donc constituer une stratégie thérapeutique intéressante dans les LAM. Je me suis ensuite intéressée aux effets anti-leucémiques induits par l’inhibition de la voie des pentoses phosphates (PP) et plus particulièrement au ciblage de la G6PD (glucose-6-phosphate déshydrogénase) par le composé le 6-aminonicotinamide (6-AN). En effet, une étude de flux métabolique a permis de mettre en évidence qu’une proportion importante de glucose est dirigé vers la voie des PP, laissant suggérer que l’addiction des cellules leucémiques au glucose pourrait être liée à une utilisation augmentée de cette voie annexe. J’ai alors observé que le 6-AN induit une cytotoxicité in-vitro y compris dans les cellules primaires de patients, sans avoir d’effets sur les cellules hématopoïétiques normales et in-vivo dans un modèle de xénogreffe de la lignée MOLM-14 chez la souris NUDE. Cette étude a donc permis de montrer que l’activation constitutive de mTORC1 rend la survie des cellules de LAM dépendante de la glycolyse et crée une sensibilité spécifique à l’inhibition de la G6PD. La dérégulation de la signalisation mTORC1 étant quasi-constante dans les LAM, cibler la G6PD pourrait donc représenter une stratégie thérapeutique intéressante. / Acute Myeloid Leukemia (AML) are heterogeneous hematological diseases with poor prognosis characterized by a clonal expansion of immature progenitors. Many deregulation of signaling pathways are found in leukemic cells and give them an advantage of proliferation and survival. The MTORC1 signaling pathway, which controls protein translation, autophagy and several metabolic pathways, is constitutively activated in leukemic cells. Metabolic reprogramming in particular the "Warburg effect" is a phenomenon well described in cancer cells. High rate of glycolysis has been considered to give tumour cells advantages through rapid production of ATP and intermediates for the synthesis of nucleotides, amino acids, and lipids. In this context, I studied glucose metabolism in AML cells and the involvement of the mTORC1 signaling pathway in the deregulation of this metabolism. First, I identified by a transcriptomic analysis in the MOLM-14 cell line that mTORC1 signaling controls several metabolic pathways including those for glucose utilization. This has been verified in several AML cell lines, since inhibition or over-activation of mTORC1 respectively induces a decrease or an increase in glucose consumption and lactate production. Interestingly, the level of activation of the mTORC1 signaling pathway determines the sensitivity of AML cells to the inhibition of glycolysis. Indeed, when mTORC1 is activated, the blockade of glycolysis induces autophagy and apoptosis of leukemic cells. Conversely, blocking mTORC1 induces metabolic reprogramming of leukemic cells, which then mainly use oxidative phosphorylation to produce ATP for their needs. AML cell survival become independent of glucose. Unlike primary AML cells, survival of normal immature hematopoietic cells CD34+ is only barely affected by the blockade of glycolysis. Thus, targeting the glucose metabolism may constitute an attractive therapeutic strategy in AML. I then investigated the anti-leukemic activity induced by the inhibition of the pentose phosphate pathway (PPP) and more particularly by the specific blockade of G6PD (glucose 6-phosphate dehydrogenase) with the 6-aminonicotinamide (6- AN) compound. Indeed, a metabolic flux analysis demonstrated that a significant proportion of glucose was directed towards the PPP. This result suggested that the addiction of leukemic cells toward glucose might be related to an increased use of PPP. I then observed that the 6-AN induced in vitro cytotoxicity including in primary AML cells from patients without effect on normal immature hematopoietic cells CD34+ and in vivo in a xenograft model of MOLM-14 cell line in the NUDE mouse. This study therefore demonstrated that the constitutive activation of mTORC1 makes AML cells survival dependent on glycolysis, and creates a specific vulnerability to the inhibition of G6PD. Given that deregulation of the mTORC1 signaling pathway is almost constant in AML, targeting G6PD may therefore represent an interesting therapeutic strategy.

No description available.

Thesis (Ph. D.)--Institute of Paper Chemistry, 1942. / Includes bibliographical references (p. 106-107).

Thesis (Ph. D.)--Institute of Paper Chemistry, 1976. / Includes bibliographical references (p. 138-139).

Cancer is the second disease leading cause of death in industrialized countries. Although early detection and more efficient drugs are responsible of the reduction of mortality, several cancers still present difficult treatments and low survival rates. Conventional drugs only exhibit moderate therapeutic index between cancer and normal tissues but recent advances are focused to improve lesstoxic treatments. Hence, new drugs must target specific signaling pathways involved in cell growth and proliferation. Concerning this aim, two mechanism involved in cancer disease, named apoptosis (or programmed cell death) and pentose phosphate pathway, have been selected in this work to search new inhibitors to target crucial proteins of both cell routes.Overexpression of antiapoptotic genes has been correlated with tumor growth and resistance tochemotherapy, thus many efforts have been done to block the activity of XIAP and Survivin, central proteins acting in apoptosis and studied in the present work. Moreover, the two most active proteins detected in both the oxidative and nonoxidative branches of the pentose phosphate pathway, Glucose-6-Phosphate Dehydrogenase (G6PDH) and Transketolase (TKT), have been also selected in this thesis.Molecular Modeling methods, covering topics in protein and peptide recognition, molecular dynamics, pharmacophore generation, database searching, docking and scoring in virtual screening and binding free energy prediction, have been applied with success to discover new active molecules inhibitors of XIAP, Survivin, G6PDH and TKT proteins. / TÍTULO: "Ruptura del reconocimiento proteína-proteína en rutas tumorales mediante modelizaciónmolecular".TEXTO:El cáncer es el segunda causa de muerte por enfermedad en los paises industrializados. A pesar de la existencia de métodos eficaces de detección precoz y tratamientos cada vez más efectivos responsables de la reducción de mortalidad, algunos tipos de tumores presentan todavía tratamientos difíciles y bajos índices de supervivencia. Los fármacos convencionales sólo exhiben un índice terapéutico moderado, entre células sanas y tumorales, por ello los avances recientes se centran en encontrar tratamientos menos tóxicos para esta enfermedad. Así pues, los fármacos del futuro deberán incidir en rutas biológicas específicas, involucrando el crecimiento celular y laproliferación descontrolada. Siguiendo este planteamiento, en este trabajo se han seleccionado dos mecanismos biológicos involucrados en el cáncer, llamados apoptosis (o muerte celular programada) y ruta de las pentosas fosfato, con el objetivo de encontrar nuevos inhibidores de las proteínas más sensibles de ambas rutas.La sobreexpresión de genes antiapoptóticos se ha correlacionado con el crecimiento tumoral y laresistencia a los tratamientos habituales. Así, se está trabajando en entender el funcionamiento de dos proteínas importantes de esta ruta, el XIAP y el Survivin, las cuales se han seleccionado en este trabajo, debido a que todavía no existen fármacos en el mercado que actúen sobre estas dos proteínas y debido a que su interés terapéutico se ha demostrado claramente.Por otro lado, en este trabajo también se han estudiado las dos proteínas más activas detectadas en la rama oxidativa y no oxidativa de la ruta de las pentosas fosfato, la Glucosa-6-Fosfato Deshidrogenasa y la Transketolasa.El objetivo principal ha consistido en aplicar métodos de la Modelización Molecular, que cubrentópicos recientes, como el reconocimiento de péptidos y proteínas, la búsqueda en bases de datos, el anclaje y evaluación del cribado virtual de compuestos y la predicción de energías libres de unión, para encontrar nuevos inhibidores de las proteínas XIAP, Survivin, Glucosa-6-Fosfato Deshidrogenasa y Transketolasa.

Submitted by Jos? Henrique Henrique (jose.neves@ufvjm.edu.br) on 2018-06-28T22:53:24Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) jessica_pereira_matos.pdf: 1785661 bytes, checksum: f5dbf30e3ce913eae470d1e958272e42 (MD5) / Approved for entry into archive by Rodrigo Martins Cruz (rodrigo.cruz@ufvjm.edu.br) on 2018-07-18T12:52:05Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) jessica_pereira_matos.pdf: 1785661 bytes, checksum: f5dbf30e3ce913eae470d1e958272e42 (MD5) / Made available in DSpace on 2018-07-18T12:52:05Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) jessica_pereira_matos.pdf: 1785661 bytes, checksum: f5dbf30e3ce913eae470d1e958272e42 (MD5) Previous issue date: 2017 / Na produ??o do bioetanol lignocelul?sico, as hexoses provenientes da celulose s?o fermentadas a etanol por muitos micro-organismos que ocorrem naturalmente. Entretanto, as pentoses, provenientes da hidr?lise da hemicelulose, como xilose e arabinose, s?o fermentadas a etanol por poucas esp?cies selvagens conhecidas e com baixos rendimentos. H?, portanto, necessidade de sele??o de estirpes de leveduras que sejam capazes de fermentar pentoses e glicose conjuntamente e de forma eficiente. Neste estudo, duas linhagens de leveduras, Candida akabanensis UFVJM-R131 e Galactomyces geotrichum UFVJM-R10, foram avaliadas na fermenta??o alco?lica da fra??o hemicelul?sica de torta de girassol solubilizada por hidr?lise com ?cido dilu?do. A hidr?lise da hemicelulose foi realizada misturando-se 31% de biomassa seca em solu??o de H2SO4 a 6%, que foi mantida por 38 minutos a temperatura de 121?C a 1 atm. A caracteriza??o cromatogr?fica do hidrolisado obtido revelou a exist?ncia de glicose (7,57 g L-1), xilose (19,53 g L-1) e arabinose (8,85 g L- 1), al?m de 5-hidroximetilfurfural (0,71 g L-1), furfural (0,05 g L-1) e ?cido ac?tico (5,27 g L- 1). Ambas as leveduras mostraram-se capazes de produzir etanol a partir do hidrolisado ?cido da torta de girassol. Os processos conduzidos com as leveduras G. geotrichum UFVJM-R10 e C. akabanensis UFVJM-R131 apresentaram valores de YP/S de 0,29 e 0,27 g etanol g-1 a??cares, respectivamente. As quantidades dos inibidores identificados no hidrolisado n?o afetaram a efici?ncia da fermenta??o alco?lica. A suplementa??o do hidrolisado com fontes de nitrog?nio e minerais aumentou a taxa de consumo da xilose e da arabinose. Os resultados obtidos permitiram concluir que as linhagens G. geotrichum UFVJM-R10 e C. akabanensis UFVJMR131 possuem potencial para a produ??o de bioetanol a partir da fra??o hemicelul?sica de biomassas vegetais. / Disserta??o (Mestrado) ? Programa de P?s-gradua??o em Biocombust?veis, Universidade Federal dos Vales do Jequitinhonha e Mucuri, 2017. / In the production of bioethanol lignocellulosic, the hexose from cellulose are fermented to ethanol by many microorganisms that occur naturally. Though, the pentoses from hemicellulose hydrolysis, as xylose and arabinose, are fermented to ethanol by few known wild strains. This fact point the need to select strains of yeasts capable of ferment pentoses and glucose together more efficiently. In the present study, two lineages of yeast, Candida akabanensis UFVJM-R131 and Galactomyces geotrichum UFVJM-R10, were evaluated on alcoholic fermentation of hemicellulosic fraction from sunflower cake solubilized by hydrolysis with dilute acid. The hydrolysis of hemicellulose was performed utilizing 31% of dry biomass in H2SO4 at 6% under 121?C and pressure at 1 atm for 38 minutes. Chromatographic characterization of the hydrolyzate obtained showed the presence of glucose (7.57 g L-1), xylose (19.53 g L-1) and arabinose (8.85 g L-1), besides 5-hydroxymethylfurfural (0.71 g L-1), furfural (0.05 g L-1) and acetic acid (5.27 g L-1). Both yeasts were able to produce ethanol from the acidic hydrolyzate. The fermentation carried out with G. geotrichum UFVJM-R10 and C. akabanensis UFVJM-R131 presented YP/S values of 0.29 and 0.27 g ethanol g-1sugars, respectively. The amounts of the inhibitors identified in the hydrolyzate did not affect the efficiency of the alcoholic fermentation. The supplementation of the hydrolyzate with nitrogen and mineral sources increased the rate of consumption of xylose and arabinose. The results obtained allowed to conclude that the strains G. geotrichum UFVJM-R10 and C. akabanensis UFVJM-R131 have potential for the production of bioethanol from vegetal hemicellulosic fraction.

Orientadores: Francisco Maugeri Filho, Daniel Ibraim Pires Atala / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-26T00:40:02Z (GMT). No. of bitstreams: 1 Farias_Daniele_D.pdf: 6531706 bytes, checksum: 72d6eac9b0705d092d687f0e643efe07 (MD5) Previous issue date: 2014 / Resumo: A produção biotecnológica de etanol de segunda geração (2G) mediante o cultivo de Scheffersomyces stipitis a partir de pentoses de hidrolisados hemicelulósicos de resíduos agroindustriais é de grande interesse econômico. Isso porque esse processo pode agregar valor a estes resíduos, possibilitando substituir os combustíveis fósseis, além de promover um aproveitamento mais completo dos materiais. Somando-se a isso, a utilização de meios fermentativos com alta concentração de substrato é de grande interesse para a indústria, pois diminui de forma significativa o volume das dornas e da vinhaça. As grandes quantidades de etanol no meio consomem menos energia no processo de extração. Porém, esta alta concentração de etanol inibe o processo, surgindo necessidade do mesmo ser retirado do meio enquanto é produzido. A utilização de técnicas de extração melhora o desempenho do processo. O uso do evaporador flash possibilita usar altas concentrações de açúcares, o que tem como consequência maior produção de etanol, reduzindo o custo da destilação. Diante disto, o objetivo dest trabalho foi o de desenvolver uma tecnologia alternativa para transpor os gargalos hoje existentes na produção de etanol 2G a partir de pentoses através de um processo fermentativo com retenção de células, acoplado a um evaporador a vácuo tipo flash. O protótipo proposto possibilitou investigar a produção de etanol a partir de xiloses, em processo utilizando alta concentração celular de S. stipitis. A razão do emprego desta tecnologia se deve à baixa tolerância do micro-organismo ao etanol e à baixa produtividade. Inicialmente foram realizados estudos visando investigar os efeitos inibitórios da concentração de etanol e de substrato no comportamento cinético da linhagem S. stipitis. Para tal, foram realizados experimentos no modo batelada e contínuo, com concentração de substrato variando na faixa de 7,5 a 145 g.L-1. Os resultados comprovaram o forte efeito inibitório sobre a velocidade específica de crescimento celular, de consumo de substrato e de etanol produzido quando administradas elevadas concentrações de substrato, bem como quando acumulados altas concentrações de etanol. Com base nestes dados foi desenvolvido um modelo matemático misto, o qual combina os modelos de Andrews e Levenspiel para descrever os efeitos inibitórios da concentração de substrato e etanol, respectivamente. O modelo cinético foi capaz de descrever satisfatoriamente o perfil cinético dos dados experimentais.. Fez-se uma análise de sensibilidade paramétrica através do auxílio de um planejamento Plackett-Burman usando o software Statistica, variando os parâmetros cinéticos e avaliando o efeito desta variação nos perfis de concentração celular, substrato e etanol. Os parâmetros idenficados como mais relevantes do modelo foram ?max, Pmax, Yx, n e Yp/x, os quais foram escolhidos para serem re-estimados sempre que houverem mudanças nas condições operacionais. Com intuito de aprimorar a produção de etanol pela linhagem S. stipitis, realizaram-se experimentos no modo batelada alimentada. Esta estratégia é utilizada para evitar a repressão catabólica do micro-organismo, bem como para assegurar uma alimentação ótima de substrato no reator. Operar o sistema com esta estratégia resultou em elevados rendimentos e produtividades para este tipo de processo. A máxima concentração de etanol obtida foi de 46 g.L-1, obtidas para concentração de xilose no meio de alimentação de 200 g.L-1. O rendimento e a produtividade foram 1.1 e 2.3 vezes superiores do que quando operados experimentos no modo batelada simples. Por fim, para testar a operacionalidade da tecnologia desenvolvida foram realizados experimentos com o intuito de avaliar a eficiência do `retentostato extrativo a vácuo¿. O efeito tóxico promovido pelo etanol em altas concentrações foi minimizado pela extração intermitente em tanque flash operado a vácuo. Esta estratégia permitiu manter uma baixa concentração de etanol no meio fermentativo (~25-35 g.L-1) e uma concentração alcóolica no condensador de 40 °GL. A máxima produtividade em etanol obtida o sistema desenvolvido foi de 1 g.L-1.h-1, obtido com 100 g.L-1 de xilose no meio de alimentação, valor este 4.35 vezes maior quando comparado aos cultivos no modo batelada simples. A tecnologia proposta aqui pode contribuir para aprimorar futuras pesquisas na produção de etanol 2G por meio do desenvolvimento de processos de baixo custo em escala industrial / Abstract: The biotechnological production of second generation ethanol (2G) through the cultivation of Scheffesomyces stipitis on pentoses obtained from hemicellulose hydrolyzates of agro-industrial wastes is of great economic interest. This is because, this process can add value to these wastes, replace fossil fuels, and promote a complete recovery of materials. Adding to this, the use of fermentation media with high concentration of substrate is of great interest to industry because it reduces significantly the volume of reactors and vinasse. Large amounts of ethanol in the culture medium consume less energy in the extraction process. However, this high concentration of ethanol inhibits the process, so its remotion during fermentation is advisable. The use of extraction techniques improves the performance of the process. The use of flash evaporator allows the use of high concentrations sugars, which results in increased production of ethanol, reducing the cost of distillation. Facing this, the objective of this study is to develop an alternative technology to bridge the currently existing bottlenecks in the production of 2G ethanol from pentoses through a fermentatiton process with cell retention, coupled to a vaccum evaporator type flash. With the proposed prototype, ethanol production from xyloses was studied in a process utilizing high cell concentration of S. stipitis. The reason for the use of this technology is due to the low tolerance of this strain to ethanol as well as the low productivity. Initial studies were conducted in order to investigate the inhibitory effects of ethanol and substrate concentrations in the kinetic behavior of the strain S. stipitis. To promote this, experiments were performed in batch and continuous mode, with substrate concentration ranging from 7.5 to 145 g.L-1. The results showed a strong inhibitory effect promoted on the specific growth rate, substrate consumption and ethanol production when high initial substrate concentrations were administered, leading to high concentrations of ethanol. Based on these experimental data, a mixed mathematical model that combines models of Andrews and Levenspiel to describe the inhibitory effect prmoted by substrate and ethanol concentrations, respectively, has been proposed. The kinetic model was able to satisfactorily describe the kinetic profile of the experimental data. However, mathematical modeling of kinetic parameters is a difficult task and it consumes a considerable period of time. A parametric sensitivity analysis was performed with the aid of a Plackett-Burman design using the Statistic software. The kinetic parameters were varied and the effect of this variation was evaluated in the cell, substrate and ethanol concentration profiles. The most relevant model parameters were ?max, Pmax, Yx, n and Yp/x, which were chosen to be re-estimated whenever there are changes in the operation conditions. In order to enhance the 2G ethanol production by strain S. stipitis, experiments were performed in fed-batch mode. This strategy was used to avoid the catabolic repression of this strain as well as to ensure optimal substrate feeding to the reactor. The operate of the system whit this strategy resulted in high concentrations of ethanol with high yields and productivities. The maximum ethanol concentration achivied was 46 g.L-1 obtained for xylose concentration in the feed medium of 200 g.L-1. The yield and productivity were 1.1 and 2.3 times higher than when operated in the batch mode. Finally, experiments were conducted to test the effectiveness of the technology developed in order to evaluate the efficiency of `extractive retentostato vacuum¿. The toxic effect caused by high ethanol concentrations was minimized by intermittent extraction in the flash tank operated on vacuum. This strategy allowed maintaining a low concentration of ethanol in the fermentation medium (~25 ¿ 35 g.L-1) and an alcohol concentration in the condenser at 40°GL. The maximum ethanol productivity obtained was 1 g.L 1.h-1, obtained with 100 g.L-1 of xylose in the feed medium, and this value was 4.35 times higher compared with experiments performed in bacth mode. The technology proposed here may contribute to enhance future research in 2G ethanol production through the development of processes for low cost industrial scale / Doutorado / Engenharia de Alimentos / Doutora em Engenharia de Alimentos

Mes travaux de thèse se sont portés sur les cellules pyramidales du néocortex de rongeur, en condition normale et pathologique. L'altération précoce du métabolisme du glucose est une caractéristique fonctionnelle invariante de la maladie d'Alzheimer (MA) qui pourrait être à l'origine des dysfonctionnements synaptiques et de la neurodégénerescence tardive associés à la maladie. Pour mieux comprendre la pathogenèse de la MA, j'ai cherché à clarifier les mécanismes responsables de l'hypométabolisme précoce du glucose observé dans la maladie. Mes travaux ont mis à jour des altérations des flux métaboliques du glucose chez un modèle murin de la MA à un stade asymptomatique juvénile. Les données d'imagerie cellulaire révèlent une augmentation du flux glycolytique associée à une diminution de l'activité de la voie des Pentoses Phosphates dans les cellules pyramidales néocorticales des souris 3xTg-AD sans altération du transport du glucose. Le système noradrénergique exerce une profonde influence sur les processus cognitifs. Une partie de ma thèse a été consacrée à éclaircir les effets de la NA sur la modulation de l'excitabilité des cellules pyramidales dans le cortex somatosensoriel de souris. Mes résultats montrent que les agonistes α1 et β noradrénergiques inhibent les courants responsables de l'hyperpolarisation lente qui suit les potentiels d'actions et suggèrent un effet coopératif des récepteurs α1 et β noradrénergiques. L'implication des récepteurs α1 dans la genèse d'une dépolarisation lente post PA reste à déterminer. Ces deux phénomènes convergeraient vers une dépolarisation accrue de la membrane du neurone, facilitant une nouvelle décharge de PA. / During my thesis, I focused on the neocortical pyramidal cells in normal and pathological condition. The early alteration of glucose metabolism is an invariant feature of Alzheimer's disease ( AD) which might lead to the late synaptic dysfunctions and neuronal loss related to the pathology. To better understand the AD pathogenesis, I sought to clarify the mechanisms responsible for the early glucose hypometabolism observed in the pathology. This work has highlighted alterations in glucose fluxes at a juvenile presymptomatic stage in a mouse model of AD. The cellular imaging data revealed an increase of the glycolytic pathway associated with a reduction in the PPP in pyramidal neurons of 3xTg-AD mice without any alteration of glucose transport. The noradrenergic system has a significant influence on cognitive processes. A part of my thesis has been devoted to highlight the effect of noradrenaline on pyramidal cells' excitability in the mouse somatosensory cortex. My results show that α1 and β noradrenergic agonists inhibit the currents responsible for sAHP and suggest a cooperative effect of α1 and β noradrenergic receptors. The RA-α1 involvement in the genesis of a slow After Depolarization has yet to be determined. Those two phenomena will lead to an increased depolarization of neuronal membrane, facilitating a novel action potential discharge.