Dissertations / Theses on the topic 'Enzymes – Composition chimique'
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Nicolas, Anne. "Etudes structure-fonction d'une cutinase recombinante de Fusarium solani pisi." Aix-Marseille 2, 1996. http://www.theses.fr/1996AIX2A002.
Full textDupille, Éve. "Purification et caractérisation de l'enzyme formant l'éthylène chez la pomme." Toulouse, INPT, 1992. http://www.theses.fr/1992INPT021A.
Full textBernard, Pascale. "Synthèse par voie enzymatique : étude comparative de milieux réactionnels." Vandoeuvre-les-Nancy, INPL, 1995. http://www.theses.fr/1995INPL002N.
Full textDiakou, Paraskevi. "La phosphénolpyruvate carboxylase de la baie de raisin (Vitis vinifera L. ) : étude biochimique, métabolique et immunocytochimique." Bordeaux 2, 1999. http://www.theses.fr/1999BOR20675.
Full textOzenne, Catherine. "Biofaçonnement de la matière grasse du lait." Montpellier 2, 1993. http://www.theses.fr/1993MON20159.
Full textLofty, Samia. "Etude des hydroxycinnamoyl-CoA : transférases : purification, spécificité et intervention dans la biosynthèse des esters hydroxycinnamiques chez les végétaux." Montpellier 2, 1991. http://www.theses.fr/1991MON20212.
Full textDebray, Laurence. "Nutrition du lapereau en période de sevrage : interaction avec les besoins nutritionnels de la femelle." Toulouse, INPT, 2002. http://www.theses.fr/2002INPT005A.
Full textKibelolaud, Aimé Robert. "Incidence du traitement thermique et de la taille des particules sur la digestion des protéines des graines du lupin : Lupinus albus : étude in situ chez la vache laitière." Toulouse, INPT, 1992. http://www.theses.fr/1992INPT025A.
Full textBleta, Rudina. "Systèmes fluorés pour la conception de matériaux poreux : Matrices pour la physisorption de biomolécules." Thesis, Nancy 1, 2007. http://www.theses.fr/2007NAN10111/document.
Full textThe self-assembly properties of surfactants and those of silica chemistry have led to the preparation of ordered mesoporous materials with hexagonal, cubic or lamellar symmetry and with pore sizes varying from 2 to more than 10 nm. Recently, they have aroused of great deal of interest to academics and industrialists for the development of fundamental and applied research. However, their use in any industrial process needs a careful consideration of the total comprehension of the synthesis mechanism as well as the control of their structural and textural properties. In this work, the relation between the physicochemical properties of a fluorinated surfactant, C7F15C2H4(OC2H4)8OH, and the characteristics of mesoporous silica was investigated. In spite of the existence of a micellar phase, only wormlike mesoporous materials were obtained. On the other hand, the addition of the perfluorodecalin led to the organisation of the channels according to a hexagonal symmetry. The use of various fluorocarbons of different molecular structures evidenced that this phenomenon is associated to the shift of the cloud point curve towards higher temperatures. Hierarchically porous silica were also prepared from oil-in-water emulsions and their characteristics were correlated to the phase inversion temperature of the surfactant/water/oil system. Finally, the mesoporous materials were used as hosts for the physisorption of enzymes and the results showed that the catalytic activity of the immobilised lipases is preserved
Herbaut, Mickaël. "Déconstruction de la biomasse lignocellulosique : corrélations entre l’activité et la mobilité enzymatiques." Thesis, Reims, 2017. http://www.theses.fr/2017REIMS047.
Full textBiomass recalcitrance to enzymatic hydrolysis is a multifactorial phenomenon still challenging to understand. The main objective of this work was to determine factors that could be considered as generic markers of this recalcitrance. The relationship between enzymes dynamics and cell wall chemical and structural properties was studied using a panel of contrasted biomass samples (wheat straw, miscanthus, poplar) submitted to four different pretreatments, using a combination of chemical, spectroscopic and microscopy analyses.Lignin structure and composition were found to be the main factors explaining recalcitrance for all three biomasses, as highlighted by the negative correlations between fluorescence intensity and glucose yield. Increasing porosity improves saccharification differently for each species reflecting the different organisation of their cell walls. Mobility measurements of probes representative of enzyme size revealed that pretreatments have a more important impact on cell wall structure than the subsequent saccharification. Both the activity and mobility of enzymes are governed by pores sizes whose diameter need to be at least 5 times the diameter of the enzymes for the catalyst to diffuse efficiently in the cell wall, likely due to a fill-in effect caused by interactions with lignin. The intertwining between lignin and pores sizes was emphasized by measurements of the probes interactions with lignin revealing that binding depended on lignin structure, but also on its accessibility and on cell wall porosity.Our strategy and results provide insights for the improvement of pretreatment methods allowing a better valorisation of lignocellulosic biomass
Bzdrenga, Janek. "De la promiscuité des enzymes : cas des PLLs et de leur implication dans l'anti virulence bactérienne et la décontamination des organophosphorés." Thesis, Aix-Marseille, 2016. http://www.theses.fr/2016AIXM5018.
Full textPhosphotriesterase-Like Lactonases (PLLs) are a family of enzyme displaying a dual catalytic activity. Lactonase activity allows for, among others, the destruction of Acyl Homoserine Lactones (AHLs). These molecules mediate the communication in Gram negative bacteria, allowing them to synchronize group behavior like virulence factor secretion or biofilm formation. Beside their ability to hydrolyze molecules with a lactones moiety, PLL also show substrate promiscuity for hydrolyzing highly toxic organophosphate compounds (OPs), such as pesticides (i.e. Paraoxon) or Chemical Warfare Nerve Agents (CWNAs) (e.g. Sarin & VX). The work described here consisted in evaluating the efficacy of the PLL SsoPox, originating from the extremophile Archaea Sulfolobus solfataricus, to prevent virulence and biofilm formation on the model strain Pseudomonas aeruginosa PAO1. This evaluation was performed both in vitro and in vivo, by using a rat pulmonary infection model. A study has been performed on a strain collection of 73 clinical strains of P. aeruginosa isolated from diabetic foot, to assess the enzyme effects on pyocyanin secretion and protease activity. Finally, a prospective phase to identify new PLLs allowed for the enzymatic and structural characterization of two new enzymes, SacPox and VmoLac, thus contributing to refine the knowledge about this enzyme family and their engineering potential. In conclusion, PLLs are of prime biotechnological interest and could lead to developments in human health, but also for OPs bioremediation with a non aggressive decontamination solution
Uzel, Alexandre. "Caractérisation fonctionnelle des formiate-déshydrogénases de Bacillus subtilis par spectroscopie RPE." Electronic Thesis or Diss., Aix-Marseille, 2022. http://theses.univ-amu.fr.lama.univ-amu.fr/220310_UZEL_750yyya237ggtlq644ueoq380vkulm_TH-1.pdf.
Full textNowadays one of the biggest environmental challenges is the bioremediation of atmospheric CO2. The biocatalytic reduction of CO2 to formate by microbial formate dehydrogenases (FDHs) is very promising. We present the EPR characterization of two similar FDHs, named ForCE 1 and ForCE 2, from the soil bacterium Bacillus subtilis. These enzymes belong to the Mo/W-bisPGD (i.e. pyranopterin guanosine dinucleotide) superfamily, which is widespread in prokaryotes. These two FDHs appear to be of great scientific interest for several reasons : sequence analyses reveal that their active site harbours non-consensual residues for formate-dehydrogenase activity, defining a new FDH sub-familly not yet characterised. Moreover, the way in which these enzymes are integrated into the metabolism of this organism remains to be established, leaving the door open for new biological discoveries. The catalytic core of ForCEs is composed of two subunits. From sequence analysis, the larger one (ForC) is thought to coordinate five iron-sulfur clusters and a Mo-bisPGD while ForE does not appear to harbor any cofactor. By combining redox potentiometry, multifrequency continuous wave (CW) and pulsed EPR spectroscopy, we were able to characterize the EPR signatures and redox properties of several paramagnetic cofactors in the purified enzymes including at least four FeS clusters (the fifth was detected by spin quantitation) and two MoV species associated to the molybdenum cofactor. An unexpectedly intense radical signal was also detected and could be attributed to a highly stabilized menasemiquinone species based on its redox and spectroscopic properties determined by a multi-frequency EPR approach
Jacquet, Pauline. "Amélioration d'une enzyme hyperthermostable pour la dégradation des organophosphorés." Thesis, Aix-Marseille, 2017. http://www.theses.fr/2017AIXM0618/document.
Full textOrganophosphates (OPs) are neurotoxic compounds widely used as pesticides. Over the years, utilization of OP led to a considerable environmental contamination of soils and agricultural wastewaters, this pollution is furthermore a major health issue as these insecticides can be found in food. OP are highly toxic and are responsible for 300,000 deaths in the world every year. OPs were also developed as chemical warfare nerve agents such as sarin. Currently, no satisfying method for external decontamination is available, therefore bioremediation with enzymes is highly appealing. Among OP degrading enzymes, phosphotriesterases (PTEs) are the most active biocatalysts but are poorly stable what hinders their potential for bioremediation. Hyperthermostable enzymes from extreme environments were thus considered to circumvent this limitation. In particular, SsoPox isolated from the archaeon Sulfolobus solfataricus, displaying a lactonase activity and a promiscuous phosphotriesterase activity was deeply investigated. SsoPox is extremely robust but its activity for OP degradation is from far lower. A protein engineering strategy was started in order to reach a compromise between PTE activity and SsoPox robustness. Using structural similarities between PTEs and SsoPox, a mutational database was designed in order to transfer the highly performant active site of PTE into the hyperstable scaffold of SsoPox. This strategy led to variants displaying up to 2,000-fold increase against OPs as compared to wild-type enzyme. The variants efficiency was demonstrated in vivo using an original animal model planarian, allowed to enhance survival rate as well as mobility and regeneration capacity
Michelutti, Isabelle. "Variations des cellules somatiques et de la composition biochimique du lait en relation avec l'inflammation expérimentale de la glande mammaire." Vandoeuvre-les-Nancy, INPL, 1998. http://www.theses.fr/1998INPL138N.
Full textLegentil, Anne. "Étude de la composition chimique des pectines de la paroi cellulaire de la fraise et de leur solubilisation par des préparations enzymatiques industrielles : application à la liquéfaction de la fraise." Vandoeuvre-les-Nancy, INPL, 1996. http://www.theses.fr/1996INPL018N.
Full textPuspita, Maya. "Extraction assistée par enzyme de phlorotannins provenant d’algues brunes du genre Sargassum et les activités biologiques." Thesis, Lorient, 2017. http://www.theses.fr/2017LORIS440/document.
Full textIn France and Indonesia, Sargassum is quite abundant yet this alga has not been optimally exploited. Sargassum contains macro and micro molecules and also bioactive compounds, the most known is phlorotannins, showing a wide range of pharmacological properties. Therefore, it is interesting to further valorize this alga. The heterogeneity and complexity of algal cell wall strongly reduces the extraction efficiency application of conventional extraction. Subjects of interest in this study were to characterize the seasonal variation of Sargassum biochemical composition and to extract phlorotannins using conventional and alternative method, i.e. solid-liquid and enzyme- assisted extraction. In this study, minerals represented a significant value with a content reaching 33% followed by proteins with 24% of algal dry material. In the contrary, sugars showed only 13% of algal dry material. Further, the biochemical composition of Sargassum, like most algae, was highly affected by the seasons and related to Sargassum life cycle. In terms of polyphenol compounds in Sargassum, season might be the most influential factor but suitable methods of extraction determine the efficiency to collect these compounds from Sargassum. Solid-liquid extraction, in certain extent, yielded lower (ranging from 5 to 24% of dry algal material) than the enzyme-assisted extraction (ranging from 21 to 38% of dry algal material). Concerning the polyphenol content of Sargassum extracted with these two methods, enzyme-assisted extraction, in certain extent, had higher content than the solid-liquid extraction. Enzymatic extracts showed a strong antiradical activity
Kader, Farid. "Analyse des transformations oxydasiques (PPO, POD) responsables du brunissement et de la dégradation des pigments anthocyaniques des jus de bluet (Vaccinium corymbosum, L. ) : caractéristiques des principaux constituants du fruit : importance de la contribution des intermédiaires quinoniques." Vandoeuvre-les-Nancy, INPL, 1996. http://www.theses.fr/1996INPL131N.
Full textConnolly, Siobhan. "Etude biochimique et physicochimique de gommes végétales exsudées par Acacia senegal et Combretum nigricans." Rouen, 1988. http://www.theses.fr/1988ROUES005.
Full textLe, Deun Erell. "Couleur des jus de pomme et des cidres : analyse structurale et impact de plusieurs paramètres physico-chimiques." Thesis, Rennes 1, 2016. http://www.theses.fr/2016REN1B047/document.
Full textThe phenolic compounds are involved in the main organoleptic properties of plant-derived foods. They are especially responsible for the bitterness, the astringency and the color of apple cider products. The browning observed during fruit processing is related to the formation of yellow-orange pigments. By its catalytic activities, the polyphenol oxidase, a plastidial enzyme, initiates the oxidation of polyphenols in the presence of oxygen. It leads to the formation of quinones, very reactive species which are quickly involved in further chemical reactions. Some of the neoformed products are colored. Four apple juices, showing contrasted colors, were analyzed by reversed-phase HPLC-DAD-MS in order to obtain their profiles in colored compounds. The presence of yellow-orange oxidized tanning and non-tanning compounds was highlighted. Within the latter compounds, some phloridzin oxidation products, deriving from dihydrochalcones, were clearly identified (POPj, XGPOPj). In parallel, coupled approaches in real media and model solutions led to the identification of a new colored structure deriving from an oxidative coupling between a dihydrochalcone and a flavanol monomer. Finally, catechin trimers were also characterized in synthetic medium but they were not detected directly in apple juices. Moreover, the color expressed by the yellow-orange pigments can suffer some variations as a function of the physical-chemical environment. For instance, the cider fermentation results generally in a loss of color in apple juices; but the composition of the fermentative medium evolves under the influence of several parameters, such as pH and redox potential. The impact of reducing conditions on the color of POPj and A-type dehydrotriepicatechin, both selected as model pigments of apple juices, was explored by cyclic voltammetry and UV-visible spectroelectrochemistry. Besides, the changes in spectral properties of POPj, related to its protonation state, were rationalized by TD-DFT calculations
Brillouet, Jean-Marc. "Purification et étude des propriétés d'endo-(1->4)-[bêta]-D-xylanases de Polyporus tulipiferae et de l'[alpha]-L-Arabinofuranosidase de Dichomitus squalens : application à l'analyse structurale d'un hétéroxylane ramifié du péricarpe du grain de blé : comparaison avec les méthodes chimiques et physique (RMN)." Grenoble 1, 1986. http://www.theses.fr/1986GRE10054.
Full textTheron, Louwrens. "Etude de l’impact de MpAPr1, une protéase aspartique de la levure Metschnikowia pulcherrima, sur les propriétés du vin." Thesis, Bordeaux, 2017. http://www.theses.fr/2017BORD0009/document.
Full textProtein removal is a key step during the production of white wine in order to avoid the possible appearance of a harmless but unsightly haze. Alternatives to the use of bentonite are actively sought because of technological, organoleptic and sustainability issues associated with its use. In this study, MpAPr1, an extracellular aspartic protease previously isolated and partially characterised from the yeast Metschnikowia pulcherrima, was cloned and expressed heterologously in Komagataella pastoris. Enzymatic properties of MpAPr1 were initially characterised in a crude extract. After several attempts using different techniques, MpAPr1 was successfully purified via cation exchange chromatography. Its activity against haze-forming grape proteins was initially tested in a model solution under optimal environmental conditions for MpAPr1 activity and under those occurring during winemaking. Thereafter, MpAPr1 activity was evaluated in grape must and throughout alcoholic fermentation. The presence of MpAPr1, supplemented to grape must, resulted in the partial degradation of grape proteins throughout fermentation and ultimately in a slight difference in the wine’s composition in volatile compounds. The study provides further evidence that aspartic proteases could represent a potential alternative to bentonite for the wine industry and that non-Saccharomyces yeasts such as M. pulcherrima could have a beneficial impact on wine properties
Bory, Sothavireak. "Étude ethnopharmacologique d'une plante utilisée en médecine traditionnelle cambodgienne dans le traitement de la malaria : stephania rotunda (Lour.) : approche analytique, phytochimique, pharmacologique et métabolique." Thesis, Aix-Marseille 2, 2010. http://www.theses.fr/2010AIX22960.
Full textAn HPLC method is developed and validated for the simultaneous determination of major alkaloids: cepharanthine,xylopinine, tetrahydropalmatine in tuber of Stephania rotunda Lour. The validated method was successfully applied toquantify the three alkaloids in various parts of the plant. The higher content of major alkaloids, in particularcepharanthine (1%), is found in the tuber of this plant. The major alkaloids of tubers from different regions aredetermined. The cepharanthine is concentrated in tuber of Pailin (1.9%). The comparison of the chemical composition ofcultivated and wild tubers shows similar results. Eight alkaloids were isolated from S. rotunda using FlashChromatography. Their structures are elucidated by MS and NMR. Cepharanthine, xylopinine, tetrahydropalmatine,palmatine and roemerine previously described are reisolated. Pseudopalmatine, stephanine, and vireakine (newaporphine alkaloid) are described for the first time in the plant. Pharmacological study of S. rotunda shows that themajority of extracts (76%) exert in vitro antiplasmodial activity against a chloroquine resistant strain of Plasmodiumfalciparum (W2) with IC50 < 5 μg/ml. Cepharanthine and pseudopalmatine display significative activity with IC50 valuesof 0.7 and 1 μg/ml, respectively. Isobol experiments are performed with W2 strain by combination of alkaloids/alkaloidsand alkaloids/antimalarial reference molecules. In vitro metabolism study of cepharanthine using human liver microsomesshows the cytochrome-dependant formation of a major metabolite M1. Enzymatic kinetics were investigated with pooledhuman liver microsomes to determine Michaelis-Menten constants. Important inter-individual variability of cepharanthinemetabolism is observed. In vitro studies indicate an important inter-species variability. The enzyme responsible for theformation of M1 metabolite is investigated. This study shows that CYP3A4 is involved in the metabolism of thecepharanthine. The structure of M1 metabolite, identified by CDI-MS/MS, corresponds to a N-desmethyle derivative ofcepharanthine
Brouard, Eloïse. "Effet de l'adaptation des pratiques culturales de la vigne en réponse au changement climatique (manipulation de la canopée, utilisation d'acide abscissique) sur le potentiel qualitatif de la baie de raisin : approches agronomique, analytique et transcriptomique : & Caractérisation fonctionnelle de VviAKR, enzyme potentiellement impliquée dans la voie de biosynthèse des méthoxypyrazines." Thesis, Bordeaux, 2018. http://www.theses.fr/2018BORD0408.
Full textGlobal climate changes have already affected and will continue to affect the physiology of grapevine, in particular the yield and berry composition at harvest, and thus ultimately the quality and typicality of the wines produced. Among the different possible strategies of adapting viticulture to climate change (changes varieties, creation of new varieties better adapted to future conditions,...), modulating berry composition at harvest through changing cultural practices, such as manipulations of the canopy (leaf / fruit ratio, grape exposure), may be a fast and efficient option as a short-term adaptation strategy.My thesis aims to find the best point of compromise between reducing the sugar level and, maintaining the acidity, phenolic compounds, and the aromatic complexity by the canopy manipulations (leaves / fruits ratio, secondary shoot removal), coupled or not with the application of abscisic acid.Different leaf / fruit ratios were studied on the Cabernet-Sauvignon cultivar in greenhouse and in vineyard within a plot of production. The berry composition analysis of primary and secondary metabolites, performed in these two experiments, made it possibleto determine that the ratio of 6 leaves remaining per cluster was the threshold value below which an effect on the primary metabolites is visible. A decrease in the sugar content was especially observed, also associated with a decrease in the concentration of total anthocyanins which are particularly important in the definition of the typicality of Bordeaux wines. The application of exogenous abscisic acid to the berries before veraison permitted to reduce the negative effects of the modification of the leaf-to-fruit ratio on the accumulation of anthocyanins and did not affect the typicality of the wines during the tastings of the microvinifications carried out during this study. These analytical results were coupled with transcriptomic analyses of RNAseq and real-time quantitative PCR (Fluidigm) to identify key genes associated with the primary and secondary metabolic pathways reacting to modulations of leaf-to-fruit ratio coupled or not with the addition of abscisic acid.Thus, the coupling modulation of the leaf-to-fruit ratio to the application of exogenous abscisic acid on the berries would be a usable method to reduce the sugar content and maintain a typicality of Bordeaux wines close to the current one.The functional characterization of a gene potentially associated with the biosynthetic pathway of methoxypyrazines, which are involved in vegetable character of grapes and wine, was also conducted. Different approaches have been tested and provided useful clues but the conclusive results are still under further confirmation