Les tanins jouent un rôle clé dans les qualités organoleptiques du vin rouge. Ils sont à l’origine de l'Astringence, une sensation de sècheresse perçue en bouche lors de la dégustation. Cette sensation est la conséquence d'une interaction spécifique entre des tanins et des protéines salivaire, principalement les Protéines Riches en Prolines (PRPs). Une première partie de ce travail a consisté à étudier l'influence de divers sucres sur le processus d'auto-association des tanins ainsi que sur les interactions tanins-protéines. Le comportement colloïdal d’un tanin (l’Epigallocatechine Gallate – EGCG), ainsi que son interaction avec un peptide modèle IB9-14 représentatif des PRPs, ont été étudiés en présence de différents sucres simples et polysaccharides. Les paramètres de l’interaction ont été déterminé pour l’ensemble des systèmes, mettant en évidence l’existence d’une interaction entre EGCG et sucres dont l’affinité semble dépendre du degré de polymérisation du sucre. Cette interaction ne perturbe pas, dans les conditions expérimentales testées, l’association entre les tanins et le peptide. Une deuxième partie de ce travail correspond à la synthèse complète de la protéine IB9 incluant la séquence peptidique d’IB9-14, et à l’étude de son interaction avec deux procyanidines : l’EGCG et le dimère B3. Cette étude a permis d’observer et de confirmer une influence de la longueur de la chaîne peptidique sur les interactions avec les tanins. / Tannins play a key role in the organoleptic qualities of red wine. They are responsible for wine astringency, a dry, rought and puker sensation perceived in the mouth while tasting. This sensation is the consequence of a specific interaction between tannins and saliva proteins, mainly Proline Rich Protein (PRPs). The first part of this work was to study the influence of various sugars on the self-association of tannins process as well as tannins - proteins interactions. The colloidal behavior of a tannin (the epigallocatechin gallate - EGCG), as well as its interaction with a representative peptide IB9-14 of PRPs was studied in the presence of various simple sugars and polysaccharides. The parameters of the interaction were determined for all systems, highlighting the existence of an interaction between EGCG and sugars whose affinity seems to depend on the sugar polymerization degree. This interaction does not interfere, under the experimental conditions tested, on the association between tannins and peptide. The second part of this work was to realize the full synthesis of the protein IB9 including the peptidic sequence of IB9-14, and to study its interaction with two procyanidins: EGCG and dimer B3. The results show and confirm the influence of the length of the peptide chain interactions with tannins.

Il a été montré que la consommation de Lactobacillus pouvait avoir des conséquences sur le poids de l’hôte, et ce, en fonction de la souche inoculée. Nous avons voulu comprendre le mécanisme par lequel ces microorganismes prolifèrent dans le tube digestif et induisent un changement de poids. Nous avons exploré la production de bactériocines permettant aux souches de Lactobacillus de croître au détriment des autres micro-organismes. Nous avons constitué une base de données de bactériocines nommée BUR et recherché les bactériocines dans les génomes de bactéries du tube digestif humain. Nous avons observé une abondance de bactériocines dans les génomes des bactéries du tube digestif, majoritairement dans les Firmicutes. Aussi, nous avons approfondi l’étude du profil métabolique des souches de Lactobacillus par une approche génomique et dans une analyse in vitro. Nous avons constaté que les souches de Lactobacillus dont la consommation induit une perte de poids possèdent des enzymes qui empêchent l'obésité en réduisant les niveaux de glucose dans le sang, les niveaux de triacylglycérols sériques, la masse corporelle et l'accumulation de graisse, tandis que les génomes des souches dont la consommation induit un gain de poids codent pour plusieurs enzymes favorisant la production de fructose, et mobilisent l'énergie et le carbone stocké dans les acides gras. De ce fait, nous pouvons dire que les espèces de Lactobacillus jouent un rôle important dans la digestion des nutriments, avec un effet direct sur le changement de poids. / It has been shown that Lactobacillus consumption could affect the weight of the host, and led consequently to significant weight gain or loss, depending on the strain. We wanted to understand the mechanism by which these microorganisms induce weight change. We explored the various known mechanisms, including the production of bacteriocins, allowing Lactobacillus strains to grow at the expense of other microorganisms. We established a bacteriocin database, named BUR, and search for bacteriocins in the genomes of human gut bacteria. We observed an abundance of bacteriocins in the genomes of bacteria in the digestive tract, predominantly in Firmicutes. We also have deepened the study of the metabolic profile of Lactobacillus strains, both by a genomic approach and in an in vitro assay, to better understand the pathophysiology of obesity. We have found that Lactobacillus strains whose consumption induces weight loss possess enzymes which prevent obesity by reducing glucose levels in blood, serum triacylglycerols levels, body weight and the accumulation of fat, whereas the genomes of strains whose consumption leads to weight gain encode several enzymes promoting the production of fructose and mobilize energy and the carbon stored in the fatty acids. Therefore, we can say that Lactobacillus species are important in the digestion of nutrients and can have a great influence on carbohydrate and lipid metabolism, with direct effect on weight change.

Made available in DSpace on 2017-07-21T18:53:09Z (GMT). No. of bitstreams: 1 Mary Dias Queji.pdf: 909281 bytes, checksum: 0364cd27c13b09019850a0944168a898 (MD5) Previous issue date: 2008-04-05 / The agro industry of the apple generates, during the processing, the pomace which is considered the main by-product. Studies show that of the total amount of fruit that is processed to obtain the apple juice, 20 to 40 correspond to this by-product, which, is usually destined as a complement in animal feed or delivered onto the soil as organic fertilizer. The chemical composition, in moist base, is constituted by moisture (80), fibers (5) and soluble solids (14) represented, mainly, by fructose, glucose and sucrose, as well as, by organic acids, represented, in the most part by malic acid. The apple pomace also presents phenolic compounds that are target nutrients of great sensory and nutritional importance. Therefore, the quantification of its constituents represents an important source of data in the characterization of apple pomace for biotechnological purposes, seeking to attribute an appropriate use for this by-product. The conventional methodologies used for the quantification of sugars, organic acids and total phenols, although being part of the routine analyses in the quality control laboratories, are onerous, time consuming and generate residues. The aim of this study was to develop a fast, versatile analytical technique, of low cost and no pollutant, using the diffuse reflectance infrared spectroscopy (DRIFTS) allied to methods of multivariate calibration (PLSR). For the construction of the multivariate models, the averages of the concentrations of the simple sugars, malic acid and total phenols were used, obtained by the conventional methodologies, as well as the data in the medium infrared spectroscopy (MID) and near (NIR), obtained in duplicate, and of the 52 spectra obtained for the samples of apple pomace, 47 made part of the set calibration and 5 of the set validation. The regression models for the prediction of the concentration of fructose, sucrose, total phenols and malic acid obtained better results in MID, with averages of relative standard errors of 3.9 (with 5 Latents Variable), 6.6 (with 5 Latents Variable), 6.4 (with 4 Latents Variable) and 5.9 (with 5 Latents Variable), respectively. Already the best capacity prediction for glucose concentration was obtained by NIR, in which the average of relative standard error was 7.4 (with 6 Latents Variable). The obtained results demonstrate the good capacity of prediction of the multivariate models based in infrared spectroscopy and characteristic advantages of the association DRIFTPLSR. / A agroindústria da maçã gera, durante o processamento, o bagaço que é considerado o principal subproduto deste setor. Levantamentos mostram que da quantidade total de fruta que é processada para a obtenção do suco de maçã, 20 a 40 correspondem a este subproduto, que, normalmente, é destinado como complemento na alimentação animal ou dispensado no solo como adubo orgânico. Sua composição química, em base úmida, é constituída por umidade (80), fibras (5) e sólidos solúveis (14), estes últimos representados, principalmente, por frutose, glucose e sacarose, bem como, ácidos orgânicos, representados, majoritariamente pelo ácido málico. O bagaço da maçã também apresenta compostos fenólicos, que são fito-nutrientes de grande importância sensorial e nutricional. Portanto, a quantificação desses constituintes representa uma importante fonte de dados na caracterização do bagaço de maçã para finalidades biotecnológicas, visando atribuir um fim mais nobre a este subproduto. As metodologias convencionais empregadas para a quantificação de açúcares, ácidos orgânicos e fenóis totais, embora façam parte das análises de rotina nos laboratórios de controle de qualidade, são onerosas, demoradas e geram resíduos. O objetivo deste trabalho foi desenvolver uma técnica analítica rápida, versátil, de baixo custo e não poluente. Para tal, utilizou-se a espectroscopia no infravermelho por refletância difusa (DRIFTS) aliada a métodos de calibração multivariada (Regressão de Mínimos Quadrados Parciais - PLSR). Para a construção dos modelos multivariados, foram utilizadas as médias das concentrações dos açúcares simples, ácido málico e fenóis totais, obtidas pelas metodologias convencionais, bem como, os dados de espectroscopia no infravermelho médio (MID) e próximo (NIR). Os espectros foram obtidos em duplicata, sendo que dos 52 espectros das amostras de bagaço de maçã, 47 fizeram parte do conjunto de calibração e 5 do conjunto de validação externa. Os modelos de regressão para a previsão da concentração de frutose, sacarose, fenóis totais e ácido málico obtiveram melhores resultados no MID, com médias de erro padrão relativo de 3.9 (com 5 Variáveis Latentes), 6.6 (com 5 Variáveis Latentes), 6.4 (com 4 Variáveis Latentes) e 5.9 (com 5 Variáveis Latentes), respectivamente. Já a melhor capacidade de previsão para a concentração de glucose foi obtida pelo NIR, na qual a média de erro padrão relativo foi de 7.4 (com 6 Variáveis Latentes). Os resultados obtidos demonstram a boa capacidade de previsão dos modelos multivariados fundamentados em espectroscopia no infravermelho e vantagens características da associação DRIFT-PLSR.