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  • 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.
1

Vitrification in sealed containers : Evaluation of a new technique (Rapid-i™) for cleavage stage embryos and blastocysts

Lannsjö, Christine January 2009 (has links)
<p>Ovarian stimulation in assisted reproduction often leads to the production of a high number of oocytes. After fertilization of these oocytes, the resulting embryos can be cryopreserved for later use. Vitrification is a recently introduced method for cryostoring embryos, showing high survival rates for both cleavage stage embryos and blastocysts. Characteristic of vitrification are high concentrations of cryoprotectants and ultra fast freezing which makes the material glassily. A major concern with vitrification has been the direct contact of the cryo-solutions with liquid nitrogen. Therefore, sealed containers have been developed and one of these is the Rapid-i™ made by Vitrolife Sweden AB.</p><p>We evaluated this new device using embryos not suitable for embryo transfer or cryopreservation for clinical purposes. Embryos at cleavage stages were first vitrified and then warmed. Outcome parameters were cryosurvival and development to the blastocyst stage. Blastocysts were randomised between the established VitroLOOP™ and the Rapid-i™ as carriers. Outcome parameters were cryosurvival and further development. Our results show that Rapid-i™ gives good survival rates in vitrification for cleavage stage embryos and blastocysts.</p>
2

Vitrification in sealed containers : Evaluation of a new technique (Rapid-i™) for cleavage stage embryos and blastocysts

Lannsjö, Christine January 2009 (has links)
Ovarian stimulation in assisted reproduction often leads to the production of a high number of oocytes. After fertilization of these oocytes, the resulting embryos can be cryopreserved for later use. Vitrification is a recently introduced method for cryostoring embryos, showing high survival rates for both cleavage stage embryos and blastocysts. Characteristic of vitrification are high concentrations of cryoprotectants and ultra fast freezing which makes the material glassily. A major concern with vitrification has been the direct contact of the cryo-solutions with liquid nitrogen. Therefore, sealed containers have been developed and one of these is the Rapid-i™ made by Vitrolife Sweden AB. We evaluated this new device using embryos not suitable for embryo transfer or cryopreservation for clinical purposes. Embryos at cleavage stages were first vitrified and then warmed. Outcome parameters were cryosurvival and development to the blastocyst stage. Blastocysts were randomised between the established VitroLOOP™ and the Rapid-i™ as carriers. Outcome parameters were cryosurvival and further development. Our results show that Rapid-i™ gives good survival rates in vitrification for cleavage stage embryos and blastocysts.
3

Catalytic Glycerol Hydrogenolysis to Produce 1,2-propanediol with Molecular Hydrogen and in situ Hydrogen Produced from Steam Reforming

Liu, Yuanqing 15 April 2015 (has links)
Biodiesel has shown great promise to supplement the fossil diesel since it is a renewable energy resource and is environmentally friendly. However, the major obstacle to biodiesel large scale commercialization is the high production cost; so converting glycerol, the by-product of a biodiesel process, into value-added products is an efficient way to promote biodiesel production. 1,2-propanediol (1,2PD), also known as propylene glycol, is an important commodity chemical used for many applications such as polyester resins, liquid detergents and anti-freeze. It can be produced via dehydration of glycerol into acetol followed by hydrogenation of acetol into 1,2PD using a bi-functional catalyst. Currently high pressure gaseous hydrogen added for hydrogenation causes safety issues as well as additional costs of hydrogen purchasing, transportation and storage. Therefore, the utilization of the in situ hydrogen produced by steam reforming of a hydrogen carrier could be a novel route for this process. In this work, processes of glycerol hydrogenolysis to produce 1,2PD have been developed using different hydrogen sources, i.e. molecular hydrogen and in situ hydrogen produced by steam reforming. Three different preparation methods were attempted to prepare a Cu/ZnO/Al2O3 catalyst in a glycerol hydrogenolysis process, which were oxalate gel-coprecipitation, Na2CO3 coprecipitation and impregnation. The catalyst prepared by oxalate gel-coprecipitation showed the highest activity for production of 1,2PD. It was also found that the addition of alumina did not only improve the activity but also enhanced the stability of the Cu/ZnO catalyst as shown by the catalyst recycling experiments. The morphological and chemical properties of the catalysts were characterized via XRD, NH3 TPD, TGA and TEM. Compared with other preparation methods, the Cu/ZnO/Al2O3 catalyst prepared by oxalate gel-coprecipitation exhibited a well-mixed form for all the metals as suggested by the XRD and TGA results; the particle size of the Cu/ZnO/Al2O3 catalyst was smaller as shown in the XRD and TEM results, and also based on NH3 TPD analysis the Cu/ZnO/Al2O3 catalyst showed stronger acidic sites. When Ni was loaded onto the Cu/ZnO/Al2O3 catalyst by oxalate gel-coprecipitation, it was found that the activity for acetol hydrogenation was improved but the overall glycerol hydrogenolysis reaction was slower. This was mainly due to the reduced amount of strong acidic sites caused by the addition of Ni as observed from the NH3 TPD results. 2wt% Pd supported on a Cu/MgO/Al2O3 catalyst was used in this process. Higher reaction rate and higher 1,2PD selectivity could be obtained compared with a Cu/ZnO/Al2O3 catalyst. However, a significant deactivation was observed when the spent catalyst was used. The catalyst deactivation was mainly due to catalyst sintering during the reaction resulting in a larger particle size as suggested by XRD results. The activation energies for the glycerol hydrogenolysis reaction using Cu/ZnO/Al2O3 and Pd supported on Cu/MgO/Al2O3 catalysts have been calculated. The activation energy was calculated to be 69.39kJ/mole using a Cu/ZnO/Al2O3 catalyst and 113.62kJ/mol using a Pd supported on Cu/MgO/Al2O3 catalyst. It is suggested that the reaction was chemically kinetically controlled using both catalysts and the reaction using the Pd supported on Cu/MgO/Al2O3 catalyst was more temperature dependent. It was found that the 1,2PD selectivity was strongly dependent on hydrogen pressure. The low 1,2PD selectivity at lower hydrogen pressure was due to the formation of by-products caused by side reactions with acetol. The kinetic data of acetol hydrogenation suggested that the acetol hydrogenation step was significantly faster than the overall reaction and hence the glycerol dehydration step was the rate-determining-step. In the glycerol hydrogenolysis process using in situ hydrogen, the activities of the Cu/ZnO/Al2O3 catalysts prepared by different methods were determined and the experimental results show that the catalyst prepared by oxalate gel-coprecipitation has the best catalytic activity for glycerol conversion and 1,2PD selectivity. With Ni loaded onto a Cu/ZnO/Al2O3 catalyst, the 1,2PD selectivity was improved and the glycerol conversion was lower. It might be because Ni could improve the steam reforming activity to produce more hydrogen, but due to the reduced strong acidic sites based on the NH3 TPD results glycerol conversion was decreased. Cu/MgO/Al2O3 catalysts prepared by oxalate gel-coprecipitation were used in this process and the activity was found to be higher, i.e. higher glycerol conversion and 1,2PD selectivity, compared with the Cu/ZnO/Al2O3 catalyst due to a higher amount of acidic sites based on the NH3 TPD results; the Cu/Mg/Al composition was optimized. When Ni was added into a Cu/MgO/Al2O3 catalyst, it was found that with only 1mole% Ni loaded, the glycerol conversion was lower than that without Ni loaded and the 1,2PD selectivity was slightly improved; when the Ni loading was increased to 5mole%, the catalyst was almost completely inactive, since when 5mole% Ni was loaded, the acidic sites were almost completely eliminated as observed from the NH3 TPD results. When Pd was added onto a Cu/MgO/Al2O3 catalyst the 1,2PD selectivity was significantly improved. When Pd was loaded, more surface hydrogen atoms were provided as observed from the H2 TPD results. Cu/ZnO/Al2O3 and Cu/MgO/Al2O3 catalysts have been recycled and reused to investigate the stability of the catalysts. All the catalysts were deactivated after they were recycled and reused, since it was apparent that catalyst sintering occurred during the reaction resulting in a larger particle size based on the XRD results. The deactivation of the spent catalyst was also possibly due to the formation of carbonate when the metals were contacted with CO2 which was formed via steam reforming.
4

Contrôle d'un bio-procédé par voie électrochimique : électro-fermentation du glycérol / Electrochemical control of a biological process : glycerol electro-fermentation

Moscoviz, Roman 28 February 2017 (has links)
L’électro-fermentation est un nouveau levier permettant le contrôle des procédés fermentaires à travers l'utilisation d'électrodes au potentiel contrôlé. Parmi de nombreux substrats fermentaires, le glycérol est une source de carbone largement utilisée issue de l’industrie du biodiesel, et permettant la production de molécules à valeur ajoutée comme le 1,3-propanediol. L'objectif de cette thèse est d'évaluer le potentiel de l’électro-fermentation du glycérol comme moyen de mieux maîtriser les spectres de produits fermentaires dans les procédés mettant en œuvre des cultures mixtes.La thèse étudie dans un premier temps la fermentation du glycérol en cultures mixtes afin de caractériser les principales voies métaboliques d'intérêt en réponse au paramètre environnemental le plus influent pour la fermentation du glycérol (pH). L'effet de l'introduction d'électrodes colonisées par des bactéries électro-actives, capables d'échanger des électrons avec l'électrode et d’autres microorganismes, est ensuite étudié. Ce travail est réalisé en cultures mixtes dans l'objectif d'améliorer le procédé de fermentation en termes de spécificité des métabolites formés et de leur rendement de production. Enfin, un système modèle composé d’une souche fermentaire et une souche électro-active a ensuite été conçu afin de mieux comprendre les mécanismes mis en jeu lors de l’électro-fermentation. Cette thèse ouvre de nouvelles possibilités quant à la régulation des balances redox lors de fermentation. L’électro-fermentation ainsi que l’utilisation de bactéries électro-actives ont le potentiel de devenir de puissants outils permettant d’améliorer les rendements et spécificité de production du 1,3-propanediol et d’autres molécules à valeur ajoutée. / Electro-fermentation is a novel tool allowing to control classic fermentation through the use of polarized electrodes. Among all possible fermentation substrates, glycerol is a widely used by-product from the biodiesel industry that can be converted in value-added chemicals such as 1,3-propanediol. This PhD thesis aims at evaluating the potential of glycerol electro-fermentation for the improvement of product specificity in mixed-culture fermentation.As a first step, classic fermentation of glycerol by mixed bacterial consortia was studied in order to characterize the main metabolic pathways according to the main influencing environmental parameter (pH). Then, the addition in fermentation broth of electrodes and electro-active bacteria, able to exchange electrons either with an electrode or other microorganisms has been investigated. This work was carried out in mixed-culture glycerol fermentation in order to optimize products selectivity and yields towards 1,3-propanediol. Finally, a model co-culture constituted of one fermentative and one electro-active species was used to elucidate part of the mechanisms underlying electro-fermentation. This thesis opens a whole new range of possibility regarding the regulation of redox balances in fermentation. Hence electro-fermentation and the use of electro-active bacteria could become efficient tools for improving specificity and yield of 1,3-propanediol and other value-added products in fermentation.
5

Understanding Fermentative Glycerol Metabolism and its Application for the Production of Fuels and Chemicals

Clomburg, James M. 05 September 2012 (has links)
Due to its availability, low-price, and higher degree of reduction than lignocellulosic sugars, glycerol has become an attractive carbon source for the production of fuels and reduced chemicals. However, this high degree of reduction of carbon atoms in glycerol also results in significant challenges in regard to its utilization under fermentative conditions. Therefore, in order to unlock the full potential of microorganisms for the fermentative conversion of glycerol into fuels and chemicals, a detailed understanding of the anaerobic fermentation of glycerol is required. The work presented here highlights a comprehensive experimental investigation into fermentative glycerol metabolism in Escherichia coli, which has elucidated several key pathways and mechanisms. The activity of both the fermentative and respiratory glycerol dissimilation pathways was found to be important for maximum glycerol utilization, a consequence of the metabolic cycle and downstream effects created by the essential involvement of PEP-dependent dihydroxyacetone kinase (DHAK) in the fermentative glycerol dissimilation pathway. The decoupling of this cycle is of central importance during fermentative glycerol metabolism, and while multiple decoupling mechanisms were identified, their relative inefficiencies dictated not only their level of involvement, but also implicated the activity of other pathways/enzymes, including fumarate reductase and pyruvate kinase. The central role of the PEP-dependent DHAK, an enzyme whose transcription was found to be regulated by the cyclic adenosine monophosphate (cAMP) receptor protein (CRP)-cAMP complex, was also tied to the importance of multiple fructose 1,6-bisphosphotases (FBPases) encoded by fbp, glpX, and yggF. The activity of these FBPases, and as a result the levels of fructose 1,6-bisphosphate, a key regulatory compound, appear to also play a role in the involvement of several other enzymes during fermentative glycerol metabolism including PEP carboxykinase. Using this improved understanding of fermentative glycerol metabolism as a platform, E. coli has been engineered to produce high yields and titers of ethanol (19.8 g/L, 0.46 g/g), co-produced along with hydrogen, and 1,2-propanediol (5.6 g/L, 0.21 g/g) from glycerol, demonstrating its potential as a carbon source for the production of fuels and reduced chemicals.
6

Microbial Production and Characterization of 1,3-PDO by a Novel Lactobacillus panis Strain

2012 April 1900 (has links)
Interest in the aliphatic carbon compound 1,3-propanediol (1,3-PDO) has risen over the past 15 years. In part, this interest is due to the ability of 1,3-PDO to generate a variety of industrially relevant products such as the biodegradable polymer, polytrimethylene terephtalate. Our research group previously reported the identification of a novel Lactobacillus panis PM1 isolate capable of converting glycerol to 1,3-PDO. In this body of work, the effects of various process parameters and the ability of the novel L. panis isolate to produce 1,3-PDO in static and fed-batch cultures were examined. Data collected indicated that the concentrations of glycerol, and glucose, and pH, play a vital role in the optimized production of 1,3-PDO. Optimal conditions for the production of 1,3-PDO were determined to include: i) carbon-limited culture, defined as below 50 mM glucose and ii) growth at 37°C without agitation in the presence of glycerol (150 – 250 mM) at an elevated pH of 9 – 10. Factors such as inoculum size and temperature (OD600 in the range of 0.5 – 2 and a temperature range from 15° - 37°C) in a two-step fermentation showed insignificant variance in the production of 1,3-PDO. Initial fed-batch trials reflected the importance of pH on culture viability. A pH of 8 was determined to be necessary within culture parameters for the fed-batch production of 1,3-PDO. Further, the molar concentrations of 1,3-PDO produced were found to vary only slightly between fed batch culture and a static culture. The variance of 1,3-PDO production between the static and fed-batch trials was found to be 9.1 ± 4.9 mM for an average culture producing 85.3 ± 12.0 mM of 1,3-PDO. However, the mol concentrations of 1,3-PDO produced were found to be significantly higher with 22.3 ± 1.6 versus 5.3 ± 0.7 mmol 1,3-PDO produced for the fed batch versus the static cultures, respectively. The duration of 1,3-PDO production was found to be extended in the fed-batch model of production with increased levels of 1,3-PDO being produced over 120 hours. The cloning and characterization of the recombinant 1,3-PDO NAD+-dependent oxidoreductase also were explored to gain further insight into the native production of 1,3-PDO. Initial kinetic studies determined a Km value of 1.28 ± 0.57 mM for NAD+ versus 23.8 ± 1.1 mM for 1,3-PDO. The Km values demonstrated that the availability of NAD+/NADH may be a determining factor in 1,3-PDO concentration. These findings support the literature and the conclusion that the bottleneck in 1,3-PDO production lies in maintaining an available pool of NAD+/NADH while mitigating negative effects associated with the accumulation of toxic byproducts.
7

Risque génotoxique et ovocytes. : Etude sur modèle souris de la génotoxicité des cryoprotecteurs et des protocoles de vitrification ovocytaire / Genotoxic risk and oocytes : mouse oocytes Genotoxicity assessment of cryoprotectant and oocyte vitrification protocols.

Ricou-Berthelot, Anaïs 16 September 2014 (has links)
La toxicologie génétique est une discipline qui vise à détecter des facteurs chimiques ou physiques interagissant avec l'ADN des cellules et qui, en l'absence de réparation fidèle, sont susceptibles de provoquer des mutations géniques et/ou chromosomiques. Le test des comètes est un test court de génotoxicité simple, reproductible et rapide pour étudier la survenue de lésions primaires de l'ADN. Il s'agit d'une technique micro-électrophorétique très sensible permettant la mise en évidence des lésions de l'ADN de cellules eucaryotes individuelles exposées à des agents génotoxiques. En présence de cassures de l'ADN, les fragments d'ADN ainsi formés migrent plus rapidement que l'ADN intact lors de l'électrophorèse, donnant aux noyaux cellulaires l'aspect de comètes. La cryoconservation des ovocytes matures par vitrification a de nombreuses applications: alternative à la congélation d'embryons en FIV, préservation de la fertilité avant traitement gonadotoxique, développement du don d'ovocyte. La vitrification consiste à transformer un liquide en un état vitreux et utilise des agents cryoprotecteurs (CP) à haute concentration. Plusieurs centaines de naissances d'enfants en bonne santé ont été décrites . Néanmoins peu d'études ce sont intéressées aux effets à long terme de cette technique en particulier au plan génétique. L'objectif de ce travail a été dans un premier temps de développer et de valider une technique de test des comètes sur ovocyte de souris, puis d'utiliser ce test pour évaluer la génotoxicité du PrOH sur les ovocytes de souris qu'il soit employé seul ou inclus dans les solutions de vitrifications commercialisées pour la cryoconservation d'ovocytes humains. / Genetic toxicology is a discipline that aims to detect chemical or physical factors interact with the DNA of somatic and / or germ cells and in the absence of accurate repair, are likely to cause gene and / or chromosomal mutations. The comet assay is a simple, reproductive and rapid test to study primary DNA damage. This microelectrophoretic technique, is used to visualize denatured DNA fragments migrating out of the cell nucleus during electrophoresis. The image obtained is a ''comet'' with a distinct head consisting of intact DNA and a tail containing relaxed DNA loops or broken pieces of DNA. Oocyte vitrification techniques is booming in the world, with the key to many applications: alternative to IVF embryo freezing, fertility preservation before gonadotoxic treatment, development of oocyte donation. Oocyte Vitrification traps all the aqueous solutions in a vitreous solid phase, preventing any ice crystal formation, because of very high cooling rates and high cryoprotectants concentrations. vitrification-cryopreservation has led to several hundred live births with reassuring obstetrical and perinatal outcomes. However, little is known about the possible long-term consequences on human live births after oocyte vitrification. The objective of this work was initially to develop and validate a technique comet assay on mouse oocyte, then to evaluate on mature oocytes the genotoxic effects of PrOH solution and finally the genotoxic effects of three oocyte vitrification protocols used in human ART the genotoxic of three oocyte vitrification protocols used in human.
8

Refactoring voie métabolique pour la production de synthon à partir de sources de carbone renouvelables / Refactoring metabolic pathways for synthon production from renewable carbon sources

Remedios Frazao, Claudio jose 29 October 2018 (has links)
L’ingénierie métabolique utilise des techniques de clonage pour moduler directement les voies métaboliques des microorganismes dans le but de produire des molécules d’intérêts. Précédemment envisagée pour surproduire des métabolites endogènes, l’ingénierie métabolique est aussi considérée maintenant comme une approche prometteuse pour la biosynthèse de composés non naturels par l'expression de voies métaboliques synthétiques. Cependant, malgré leur évolution au cours de millions d’années, les enzymes sont cependant peu ou pas adaptées aux nouvelles fonctions catalytiques requises par ce métabolisme synthétique. Le but de cette thèse est donc d’améliorer deux enzymes qui sont requises pour la construction et le fonctionnement de voies artificielles conduisant à la biosynthèse de molécules d’intérêts, en particulier le (L)-2,4-dihydroxybutyrate et le 1,3-propanediol, en appliquant des concepts d'ingénieries microbienne et enzymatique. / Metabolic engineering, defined as the rational engineering of organisms towards production goals, has greatly evolved since its conception over three decades ago. Once applied to overproduce cell endogenous metabolites, it is now a promising approach also for the biosynthesis of non-natural compounds through the expression of synthetic metabolic pathways. Improved over billions of years by evolution, enzymes are however less adapted to new catalytic functions as required by synthetic metabolism. The present work was aimed at the construction and optimization of artificial routes for the biosynthesis of two industrially relevant commodity chemicals (L-2,4-dihydroxybutyrate and 1,3-propanediol) through the application of concepts of enzyme rational design, directed evolution and microbial engineering.
9

Hydrogénolyse sélective du glycérol en phase aqueuse sur catalyseurs métalliques supportés / Selective hydrogenolysis of glycerol in aqueous phase over supported metallic catalysts

Noe Delgado, Séverine 11 December 2012 (has links)
Dans le contexte de la valorisation des bioressources, l'hydrogénolyse sélective du glycérol en composé C3 (propanediols, propanol, propane) est étudiée en phase aqueuse sur des catalyseurs bifonctionnels à base de ruthénium, seul ou modifié par ajouts d'étain, ou à base de platine, supportés sur alumine, alumine-silice ou oxyde de titane. Les ajouts d'étain sont effectués par différentes méthodes : co-imprégnation, imprégnation successive et réduction catalytique. La réaction d'hydrogénolyse du glycérol est réalisée en autoclave, à 210°C, P=60 bar (sous N2 ou H2), avec une solution aqueuse à 4,5% en masse de glycérol. Les conditions opératoires de cette réaction entraînent des modifications structurales et texturales des catalyseurs. Cependant, le support TiO2 est identifié comme étant celui conduisant à la meilleure stabilité de la phase métallique dans les conditions de réaction. Une plus grande acidité (de Lewis et de Brønsted) est obtenue sur les catalyseurs supportés sur alumine-silice. Pendant la transformation du glycérol, les sites acides sont impliqués dans les réactions de déshydratation sélectivement recherchées, mais peuvent promouvoir les ruptures indésirables de liaisons C-C par un mécanisme de craquage acide. La production d'alcanes s'avère relativement faible pour tous les catalyseurs testés. Les catalyseurs au Ru montrent une forte activité, mais avec une sélectivité importante en CH4. Les ajouts d'étain permettent de diminuer légèrement la formation de ce produit de dégradation indésirable. Parmi tous les catalyseurs au Pt, ceux supportés sur TiO2 montrent les meilleures conversions du glycérol et les meilleures sélectivités en produits C3 valorisable / The selective hydrogenolysis of glycerol to C3 compounds (propanediol, propanol, propane) was studied in aqueous phase on bifunctionnal catalysts composed of ruthenium, alone or modified by Sn additions, or of platinum supported on alumina, alumina-silica or titania. Tin was added by various methods: co-impregnation, successive impregnation and catalytic reduction.The glycerol hydrogenolysis was performed in batch reactor, at 210°C, 60 bar of total pressure (under N2 or H2), 4.5 wt% glycerol aqueous solution. These operating conditions involve structural and textural modifications of the catalysts. However, the TiO2 support is identified as leading to the best stability of the metallic phase in the reaction conditions. A higher acidity (Lewis and Brønsted sites) is obtained on catalysts supported on alumina-silica. During the transformation of glycerol, the acid sites are implied in the selectively intended dehydration reactions, but can promote the undesirable C-C bond cleavages by a mechanism of acid cracking. The selectivity to alkanes remains relatively low for all the tested catalysts. Ru based catalysts show a high activity with an important selectivity to CH4. Adding of tin allows to slightly decrease the selectivity to this degradation product. Among all the Pt-based catalysts, those supported on TiO2 show the best conversions of glycerol and the best selectivity to C3 valuable products.
10

Metabolic characterization of an adaptively evolved cell factory for continuous production of 1.3-propanediol and development of a new catalyst for 1.3 propanediol and acetone co-productions / Caractérisation métabolique de l'évolution adaptive d'une souche d'E. coli ingénieurée pour la production continue de 1.3 propanediol et création de nouvelles voies métaboliques pour la co-production de 1.3 propanediol et d'acétone

Tian, Liang 19 February 2014 (has links)
Les micro-organismes ont la capacité de s'adapter rapidement aux différentes contraintes environnementales ou métaboliques, mais le mécanisme détaillé et les principes de cette réponse adaptative en micro-organisme sont mal compris aux niveaux génétiques, biochimiques et métaboliques. Ici, une souche de E. coli a évolué avec un titre élevé de 1,3-propanediol a été sélectionné et cette souche a été analysée comme un exemple pour la découverte de ce processus d'évolution adaptative. La technologie de séquençage comparatif du génome entier a été utilisée pour identifier les mutations génétiques dans le chromosome et le plasmide portant les gènes codant pour la voie de production de 1,3-propanediol a également été séquencée. Quatre mutations ont été trouvées dans le chromosome et ils sont Ipd, glpR, dhak, nagD - promoteur. Une mutation a été trouvée dans le gène GGP2, qui est situé dans le plasmide. Toutes les mutations ont été en outre caractérisées par analyse génétique et inverse biochimique et leur influence dans le réseau métabolique sont aussi découverts. Nous avons démontré que tous les cinq mutations individuellement peuvent augmenter le taux de croissance et la production de 1,3 -propanediol. Selon le profil de fermentation de la souche évolué, l’accumulation d'acétate entravé la croissance de la souche et de l'augmentation de 1,3-propanediol titre. Pour optimiser la production de 1,3- propanediol, un nouveau catalyseur a été développé pour la co-production de 1,3-propanediol avec de l'acétone au lieu de l'acétate, parce que l'acétone a une plus grande valeur et est moins toxique que l'acétate. Les deux voies de l'acétate, dépendantes et indépendantes, ont été testées pour la co-production de 1,3-propanediol et l'acétone dans des conditions anaérobies. Pour la voie de l'acétate dépendante, en modifiant le niveau d'expression de l'acétate kinase cette voie était active dans des conditions anaérobies dans E. coli. Pour la voie de l'acétate indépendant, une courte chaîne acyl-CoA thioestérase candidat a été sélectionné et caractérisé, mais son activité doit encore être améliorée en utilisant l'évolution adaptative ou la sélection in vitro. Pour l'évolution adaptative, le réseau métabolique était rationnel conçu pour forcer de flux de carbone à la production d'acétone, ce qui va augmenter la possibilité et l'efficacité de la sélection d'une thioestérase avec une affinité et une activité élevée à l'acétoacétyl -CoA au cours du processus d’évolution adaptative. Pour la sélection in vitro, un système de bio-sensor a été développé afin de simplifier la méthode de sélection d'une thioestérase mutant avec une grande capacité de catalyser l'acétoacétyl -CoA in vitro. / Microorganisms have the ability to adapt rapidly to different environmental or metabolic constraints, but the detailed mechanism and the principles of this adaptive response in microorganism is poorly understood at the genetic, biochemical, and metabolic levels. Here, the glycerol pathway from S. cerevisiae and the B12-independent C. butyricum 1,3-PD pathways were introduced into E. coli and its central metabolic network was restructured to couple the production of 1.3-propanediol to the growth of the microorganism. This strain was grown in conditions favouring adaptive evolution for around 1000 hours. An evolved population was selected under optimal conditions in mineral medium. Comparing with the original strain, it can convert glucose to 1.3-PD at high molar yield (94 %) and its productivity was also significantly increased. Comparative whole genome sequencing technology was used to identify the genetic mutations and five mutating genes lpd, glpR, dhaK, nagD and GPP2 were discovered. All the mutations were further analysed and characterized to disclose their changes after the evolution and to elucidate their influence in the whole metabolic engineering network. To optimize the production of 1.3-PD further, we plan to convert the co-production of acetate to acetone. Indeed, the 1.3 propanediol production was hampered by the acetate inhibition on growth, and acetone is a valuable product which is less toxic thyan acetate. Both the acetate-dependent and independent pathways were tested to produce acetone and some modifications to adapt the global metabolic network were performed. Several strategies were applied to ameliorate the performance of acetone production. Finally, the bottleneck of the acetate-dependent acetone pathway under anaerobic condition was indentify and the acetate-independent acetone pathway still need to be improve with the selection of an evolved or mutant enzyme with high short-chain acyl-CoA thioesterase activity.

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