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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

Micropropagation "in vitro" et effets des polyamines sur la microtubérisation de l'igname du complexe "Dioscorea cayenensis - D. rotundata"

Ondo Ovono, Paul 22 October 2009 (has links)
Les Dioscorea cultivées, dont la reproduction sexuée est aléatoire, sont multipliées essentiellement par voie végétative, ce qui entraîne la dissémination dagents pathogènes dans les plantations, provoquant une baisse de rendement et de qualité des récoltes. Dans ces conditions, les besoins en semences sont rarement comblés et les possibilités dextension de la culture restent limitées. En effet, devant une demande quantitative toujours croissante et qualitative de plus en plus restrictive, les techniques classiques encore employées aussi bien pour la multiplication que pour lamélioration de la production des végétaux sont relativement lentes. En revanche, les opportunités offertes par les cultures de tissus peuvent remédier efficacement aux insuffisances et offrir des améliorations irréalisables par les autres méthodes. La multiplication en alternance par bourgeonnement axillaire à partir de nuds pendant 28 semaines et par mise en germination des microtubercules découpés pendant 16 semaines peut remédier à cette situation. Plusieurs facteurs peuvent avoir un impact sur lefficacité de cette approche: la présence ou labsence de régulateurs de croissance, la teneur en saccharose ou en éléments minéraux du milieu de culture. Dans le cadre de cette étude, les tests réalisés ont montré une formation plus précoce du tubercule en présence de polyamines et dacide jasmonique. Si les teneurs en polyamines endogènes et leur métabolisme sont significativement affectés par les polyamines exogènes, les modifications des teneurs en polyamines endogènes, quant à elles, ne peuvent être directement corrélées avec la formation du tubercule. Un retard dans la formation des tubercules lors dune réduction de la teneur en sucre du milieu de culture a aussi été constaté. Ce retard dans nest pas lié à une réduction de losmolarité du milieu de culture, comme nous avons pu le montrer en remplaçant partiellement le saccharose par du sorbitol. La putrescine et ses précurseurs larginine et lornithine favorisent aussi le développement des tubercules, ceux- ci sont plus longs et plus lourds lorsque ces composés sont ajoutés au milieu de culture à faible concentration. Une augmentation de la teneur endogène en putrescine et en auxine a été observée dans ces conditions. Laddition dacide jasmonique a un effet similaire. Une réduction du développement des tubercules est, par contre, observée en présence dune teneur en saccharose réduite. La réduction de la teneur en sucre dans le milieu de tubérisation a aussi un effet négatif sur la germination ultérieure des microtubercules. Pour pouvoir utiliser les microtubercules comme semences, il faut être assuré dun taux de germination élevé et dun stockage possible. Les microtubercules récoltés après 9 mois de culture et transférés sur un nouveau milieu sans régulateur de croissance germent très rapidement. Aucune dormance nest observée. Les microtubercules peuvent aussi être stockés pendant au moins 18 semaines. Les meilleures conditions pour une germination élevée sont une conservation à lobscurité, sous ± 50% dhumidité relative et à 25°C. Une période de dormance secondaire sinstalle une fois le stockage en cours qui varie entre 20 et 28 semaines respectivement pour les microtubercules les plus rapides et les plus lents. Seuls les tubercules de taille supérieure à 350 mm devront être utilisés pour la germination in vitro ou ex vitro.
2

Encapsulação de extratos vegetais em leito fluidizado / Encapsulation of herbal extract in fluidized bed

Benelli, Lucimara 19 February 2016 (has links)
Este trabalho objetivou investigar o processo de revestimento/aglomeração de extratos vegetais em leito fluidizado com atomização top spray, visando melhorar a estabilidade dos compostos bioativos dos extratos e suas propriedades farmacotécnicas. Açúcar cristal, pellets de açúcar e de celulose microcristalina, grânulos de celulose microcristalina, grânulos de arroz e farinha de mandioca foram utilizados como partículas sementes. Inicialmente, avaliou-se a influência do tamanho das partículas e diferentes composições de alimentação contendo extrato vegetal de Rosmarinus officinalis (alecrim). Farinha de mandioca e pellets de açúcar de diferentes granulometrias foram empregados como partículas semente. O desempenho do processo foi avaliado através da eficiência de revestimento e porcentagem de aglomeração. Os grânulos formados foram caracterizados quanto ao tamanho, fluidez e retenção de compostos bioativos (polifenóis). As formulações estudadas também foram submetidas à secagem em spray dryer para comparação entre os produtos obtidos. Os resultados obtidos mostraram que a eficiência de revestimento/aglomeração e a porcentagem de aglomeração dependem das propriedades físico-químicas das partículas sementes e das composições alimentadas. As viscosidades das formulações contendo o extrato vegetal e suas interações com as partículas iniciais influenciaram significativamente o processo. Os grânulos formados em leito fluidizado apresentaram ótima fluidez e maior retenção de polifenóis que os produtos obtidos por spray drying. Pellets de celulose microcristalina de diferentes granulometrias foram utilizados como partículas semente para investigar a dinâmica do sistema durante a encapsulação/aglomeração em leito fluidizado, por meio de análises de sinais de flutuação de pressão associados à cinética de crescimento dos grânulos e ao desempenho do processo. Dois modos operacionais foram avaliados: o modo intermitente (com interrupção da atomização da composição de alimentação em um período específico para redução do teor de umidade no sistema) e o modo contínuo (sem interrupção da atomização de alimentação). O aumento na porcentagem de aglomeração, até certo valor durante o processo, ocasionou aumento no desvio padrão nos sinais da amplitude da flutuação de pressão enquanto o sistema permaneceu estável, indicando poucas mudanças no padrão de circulação de sólidos. Este comportamento ocorreu até que a porcentagem de aglomeração atingiu um valor capaz de ocasionar instabilidades no sistema e, assim, o aumento adicional na percentagem de aglomeração acarretou o colapso do sistema. Neste momento, o desvio padrão da amplitude da flutuação de pressão tende a diminuir, sendo este comportamento mais evidente no modo operacional contínuo e com partículas semente de menor granulometria. Mudanças no desvio padrão da amplitude dos sinais da flutuação de pressão evidenciam que este método é capaz de detectar alterações na dinâmica do sistema e pode ser uma ferramenta útil para o controle e monitoramento do processo. Ensaios para avaliação da influência de diferentes variáveis operacionais, vazão de atomização e velocidade do ar de fluidização, no desempenho do processo foram realizados em modo operacional intermitente utilizando pellets de celulose microcristalina como partículas sementes. As condições operacionais mais adequadas, com maior eficiência de revestimento e menor porcentagem de aglomeração, foram selecionadas para avaliação de duas composições de alimentação contendo extrato vegetal com diferentes agentes de encapsulação, goma Arábica e concentrado proteico de soro de leite, associados à maltodextrina, ácido esteárico e Poloxamer 407. O desempenho dos processos foi avaliado através da eficiência de revestimento e porcentagem de aglomeração e os produtos quanto à fluidez e teor de compostos bioativos do alecrim: ácido cafeico, ácido rosmarínico, carnosol e ácido carnósico, determinados por HPLC-DAD. As duas formulações mostraram-se adequadas quanto ao desempenho do processo, eficiência de revestimento maior que 70% e à retenção de compostos bioativos, eficiência de encapsulação maior que 60%. Os grânulos foram submetidos testes de estabilidade acelerada e de longa duração. Os compostos bioativos sofreram degradação durante os testes com perda total de carnosol e ácido carnósico nos grânulos obtidos com as duas formulações diferentes. Também foi realizado teste de digestão gastrointestinal in vitro com os dois produtos diferentes. As concentrações de ácidos cafeico e rosmarínico não sofreram alterações significativas no decorrer do processo, tanto na simulação das condições gástricas quanto intestinais. O carnosol e o ácido carnósico sofreram perda total ao final da fase intestinal nos dois tipos de grânulos. Os grânulos com diferentes agentes encapsulantes, foram revestidos com Opadry® II visando proporcionar maior estabilidade contra degradação dos compostos bioativos. Ocorreu maior proteção do carnosol nos grânulos contendo goma Arábica submetidos ao teste de estabilidade de longa duração, a 30 °C e 75 % UR, porém esta proteção não foi efetiva para nenhum dos grânulos submetidos ao teste de estabilidade acelerada a 40 °C. Este estudo demonstrou a viabilidade do processo de encapsulação de extratos vegetais em leito fluidizado como um método promissor para produção de composições fitoterápicas com propriedades farmacotécnicas e físico-químicas adequadas. / This work aimed to investigate coating/agglomeration process of herbal extracts in fluidized bed with top spray atomization in order to improve stability of bioactive compounds and their pharmacotechnical properties. Crystal sugar granules, sugar and microcrystalline cellulose pellets, microcrystalline cellulose, cassava flour and rice granules, were used as seed particles. First, coating/agglomeration processes with cassava flour and sugar pellets as seed particles and feed compositions loaded with herbal extract of Rosmarinus officinalis (rosemary) were investigated. Fluidized bed performance was evaluated based on coating efficiency and agglomeration percentage. Products were characterized by determining the particle sizes, flow properties and retention of bioactive compounds (polyphenols). Herbal compositions were also spray dried to compare the product generated by both processes. Results showed that coating efficiency and percentage of agglomeration depend on seed particles and feed compositions physicochemical properties. The viscosity of the feed formulations and the interaction with seed particles influenced process performance. Fluidized bed granules exhibited higher efficiency of coating/agglomeration, higher retention of bioactive compounds and better flow properties than the powder obtained by spray drying. Microcrystalline cellulose pellets of different sizes were used as seed particles to investigate system dynamic during fluidized bed encapsulation/agglomeration by analysis of pressure fluctuation signals associated with growth kinetics and process performance. Two distinct operating modes were investigated: intermittent (interrupting the composition atomization for a specific period of time in order to reduce the system humidity) and continuous (without interruption of feed atomization). The increase in the agglomeration percentage to a certain value during the processes caused an increase in the standard deviation of the amplitude of the pressure fluctuations signals while the system remained stable, indicative of slight change on solids circulation patterns. However, the standard deviation of the amplitude of the pressure fluctuations signals tended to decrease when agglomeration percentage reached a value able to affect significantly the system stability, in which agglomerates growth tended to cause the system collapse. This behavior was most evident for small size seed particles and continuous operating mode. The changes in the standard deviation of the amplitude of pressure fluctuation signals showed strong evidence that this method would be able to detect changes in system dynamics and can be a useful tool for process control and system monitoring. Different operational variables, feed flow rate and fluidizing air flow rate, were used to analyze fluidized bed performance using intermittent mode and microcrystalline cellulose pellets as seed particles. Operating conditions that promoted higher coating efficiency and lower percentage of agglomeration were selected to be used in processes to evaluated different feed compositions loaded with herbal extract and encapsulating agents of two types, Arabic gum and whey protein, associated with stearic acid and poloxamer 407. Process performance was evaluated by coating efficiency and percentage of agglomeration. Products were evaluated by flow properties and the retention of bioactive compounds: cafeic acid, rosmarinic acid, carnosol and carnosic acid, determined by HPLC-DAD. Both compositions presented high coating efficiency and retention of bioactive compounds. Products were submitted to accelerated and long-term stability tests. Bioactive compounds of all granules suffered degradation during the tests with total loss of carnosol and carnosic acid. In vitro gastrointestinal digestion assays were carried out with the two types of products obtained. The concentrations of caffeic and rosmarinic acids did not change significantly during the digestion process, both in the simulation of gastric as intestinal conditions. The carnosol and carnosic acid have undergone total loss at the end of the intestinal phase in both types of products. The two types of granules with different encapsulating agents, were coated with Opadry® II aiming to provide greater stability against degradation of bioactive compounds. Higher protection of carnosol occurred in the granules containing gum Arabic subjected to long term stability test at 30 ° C, 75% RH, but this protection was not effective for any of the granules subjected to accelerated stability testing at 40 °C. The results provide strong evidence of the feasibility of the fluidised bed as a promising method for production of encapsulated phytopharmaceutical compositions with adequate pharmacotechnical and physicochemical properties.
3

Propriétés nutritionnelles et fonctionnelles des protéines de tourteaux, de concentrats et d'isolats de Ricinodendron heudelotii (Bail.) Pierre ex Pax et de Tetracarpidium conophorum (Müll. Arg.) / Nutritional and functional properties of proteins from defatted flours, concentrates and isolates of Ricinodendron heudelotii (Bail.) Pierre ex Pax and Tetracarpidium conophorum (Müll. Arg)

Mezajoug Kenfack, Laurette Blandine 07 April 2010 (has links)
Cette étude a été menée dans le but d’explorer les nouvelles sources de protéines à valeur nutraceutique. Les graines de Ricinodendron heudelotii (Bail. Pierre ex Pax) et de Tetracarpidium conophorum (Müll. Arg) ont d’abord été cuites dans de l’eau bouillante pendant 90 et 30 min qui sont respectivement leurs temps optimums de cuisson. Après délipidation et tamisage des tourteaux, la fraction 400 - 500 µm s’est révélée la plus représentative avec plus de 70 % et riche en azote protéique (6–7% MS). Les concentrats et les isolats protéiques ont été préparés à partir des tourteaux respectivement dans l’eau distillée à pH 4,5 et dans une solution de NaOH à 0,2 % (R. heudelotii), une solution de NaCl 0,6 M (T. conophorum) à pH 11. Ces concentrats (65 – 75 % MS de protéines) et ces isolats protéiques (81 – 92 % MS de protéines) ont une composition physico-chimique différente (P < 0,05) de celle des tourteaux. Pour les deux Euphorbiacées, les capacités de rétention d’eau (367 – 467 g / 100 g d’échantillon), de rétention d’huile (256 – 410 g / 100 g d’échantillon) et moussante (68 – 71 %) sont maximales dans les isolats protéiques tandis que les capacités gélifiante (6 – 14 %) et émulsifiante (63 – 87 %) le sont dans les concentrats protéiques. Les teneurs en acides aminés essentiels des tourteaux de R. heudelotii et de T. conophorum sont comparables à celle de la protéine de référence. L’étude de la digestibilité enzymatique in vitro a montré que l’azote libéré après 6 h est supérieur à 90 % dans les concentrats et les isolats protéiques. La digestibilité protéique in vivo indique que le gain de poids des rats mâles âgés de 21 ± 3 jours durant 15 jours d’expérimentation ainsi que les paramètres de rétention azotée sont plus importants avec les régimes à base de l’aliment de référence (caséine) et du tourteau de T. conophorum. Les valeurs corrigées des paramètres de digestibilité par l’indice chimique des acides aminés laissent apparaître que le tourteau de T. conophorum renferme les protéines de très bonne qualité nutritionnelle, autant que la caséine / This study was conducted in order to look for alternative sources of proteins having nutraceutic value. The grains of Ricinodendron heudelotii (Bail.) and Tetracarpidium conophorum (Müll. Arg) were first cooked in boiled water at their optimal cooking time for 90 and 30 min respectively. After defating, sieving of the defatted cakes showed that samples with a granulometry of 400 - 500 µm were most representative (more than 70%), containing more proteic nitrogen (6–7 %). Protein concentrates and protein isolates were prepared from defatted cakes respectively in distilled water at pH 4.5 and in NaOH 0.2% (R. heudelotii) and NaCl 0.6M (T. conophorum) at pH 11. Physico-chemical properties of protein concentrates (65 – 75 % of proteins) and protein isolates (81–92 % of proteins) were different from those of the defatted cakes. Water holding (367 – 467 g / 100 g of sample), oil holding (256 – 410 g / 100 g of sample) and foaming capacities (68 – 71 %) were highest with protein isolates whereas gelling (6 – 14 %) and emulsion capacities (63 – 87 %) were highest with concentrates. The amounts of essential amino acids in both defatted flours were comparable to the value in FAO / WHO (2007) scoring pattern. Nitrogen liberated after 6 h of enzymatic digestibility was more than 90 % both in the proteins concentrates and isolates. In vivo studies carried out on 21 ± 3 days old Sprague Dawley male rats for 15 days showed that gain of weight and nitrogen retention parameters were higher for rats that consumed casein and T. conophorum defatted cake. Corrected values of nitrogen digestibility of the analysed samples showed that T. conophorum defatted cake contains protein source with good nutritional quality

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