Heidelberg, Univ, Diss., 1999. / Dateiformat: tgz, Dateien im PDF-Format. - Text engl.

Heidelberg, Universiẗat, Diss., 2002. / Dateiformat: tgz, Dateien im PDF-Format.

University, Diss., 2003--Heidelberg. / Parallelt.: CsgA, a putative signal molecule of the myxobacterium Stigmatella aurantiaca involved in fruiting.

La γ-décalactone est un arôme se caractérisant par une odeur fruitée de type pêche. La littérature montre que plusieurs levures mésophiles sont capables de produire la γ-décalactone en utilisant lhuile de ricin, lacide ricinoléique et ricinoléate de méthyle comme substrat. Ce travail sest intéressé à loptimisation de la production de γ-décalactone par une levure psychrophile à partir dhuile de ricin. Dans la première partie de notre étude, après avoir comparé la production de γ- décalactone de 18 souches psychrophiles, la levure Rhodotorula aurantiaca A19 a été sélectionnée. Cette levure produit 4 lactones différentes : γ-octalactone, γ-nonalactone, γ-décalactone et γ- undécalactone. Parmi celles-ci, la γ-décalactone est le composant majeur à une concentration de 5,8 g/L en fioles alors que les autres lactones ne dépassent pas 10 mg/L. La levure psychrophile A19 a été comparée à dautres levures mésophiles du même genre. La levure mésophile 30645 produit 0,06 g/L de γ-décalactone alors que la levure 31354 ne produit aucune lactone. Les effets de plusieurs paramètres physico-chimiques comme la température, le pH et la concentration en huile de ricin ont été étudiés en comparant la croissance cellulaire et la production de γ-décalactone par les souches A19 et 30645. Nous avons également démontré que la forme R de la γ-décalactone est prédominante (99,6%). Dans la deuxième partie de ce travail, leffet inhibiteur de la γ-décalactone a été mis en évidence sur sa production ; son précurseur lacide 4-hydroxydécanoïque est beaucoup moins toxique que la γ-décalactone à légard de la cellule. Lajout de la gomme tragacanthe (3 g/L) améliore significativement la production de γ-décalactone en jouant le rôle de piège. La production de γ- décalactone par R. aurantiaca a été développée en fermenteurs de 20- et de 100-L, les concentrations atteintes sont respectivement 6,5 et 4,5 g/L. Les résultats obtenus dans la troisième partie suggèrent que la capacité de la levure psychrophile de produire la γ-décalactone est attribuée à la présence de lacyl-CoA oxydase et une thioesterase. Enfin, la γ-décalactone produite par R. aurantiaca peut être extraite du milieu de culture par adsorption sur trois résines Macronet hydrophobes (MN-100, MN- 102 et MN-202).

Submitted by (lucia.rodrigues@ufrpe.br) on 2017-03-16T13:22:52Z No. of bitstreams: 1 Edilaine Alves de Melo.pdf: 641010 bytes, checksum: 2a8032c2676a99782e8fd581d977a950 (MD5) / Made available in DSpace on 2017-03-16T13:22:52Z (GMT). No. of bitstreams: 1 Edilaine Alves de Melo.pdf: 641010 bytes, checksum: 2a8032c2676a99782e8fd581d977a950 (MD5) Previous issue date: 2012-07-27 / The bacterial fruit blotch caused by Acidovorax citrulli is one of the most severe diseases of melon (Cucumis melo), and a major problem in the Northeast, the main melon producing region of Brazil. Strategies for control of bacterial blotch include chemical and physical treatments of seeds and chemical sprays of the plant canopy. Since these treatments are not efficient and resistant melon cultivars do not exist, other strategies have been studied, including biological control. Our objectives were to analyze the efficiency of yeasts in the biocontrol of this disease by protecting seedlings and plants, and by treating melon seeds; and to verify the in vitro activity against the pathogen and the growth promotion of melon plants. None of the 60 yeasts inhibited the growth of the pathogen, but the isolates LMA1 (Rhodotorula aurantiaca), LMS (R. glutinis) and CC-2 (Pichia anomala) stood out as the most effective in protecting seedlings. When tested in plants and seeds, LMA1 and CC-2 maintained effectiveness. In plants, the reductions in disease index (ID) and area under the disease progress curve (AUDPC) compared to the control reach 58.6 and 47.2%, respectively, while seed treatments reduced ID and AUDPC up to 34.3 and 45.5%. These isolates did not promote the growth of melon plants and did not produce killer toxins in vitro. R. aurantiaca (LMA1) and P. anomala (CC-2) were effective in protecting plants and seedlings and for seed treatment of melon. Therefore, the use of these yeasts jointly with other control methods, such as resistant varieties and copper compounds, is important in integrated management of bacterial fruit blotch. / A mancha aquosa causada por Acidovorax citrulli, é uma das doenças mais severas do meloeiro (Cucumis melo) e um dos principais problemas para o Nordeste, a principal região produtora de melão do Brasil. Estratégias para o controle da mancha aquosa incluem tratamentos químicos e físicos das sementes e químico da parte aérea da planta. Uma vez que esses tratamentos não são eficientes e cultivares resistentes de meloeiro inexistem, outras estratégias têm sido investigadas, dentre elas o controle biológico. Os objetivos deste trabalho foram analisar a eficiência de leveduras no biocontrole dessa doença pela proteção de plântulas e plantas e pelo tratamento de sementes de meloeiro, além de verificar a atividade in vitro contra o patógeno e a promoção do crescimento de plantas de meloeiro. Nenhuma das 60 leveduras testadas inibiu o crescimento do patógeno, porém os isolados LMA1 (Rhodotorula aurantiaca), LMS (R. glutinis) e CC-2 (Pichia anomala) destacaram-se como os mais eficientes na proteção de plântulas. Quando testadas em plantas e sementes, LMA1 e CC-2 mantiveram a eficácia. Em plantas, as reduções de índice de doença (ID) e área abaixo da curva de progresso da doença (AACPD) em relação à testemunha foram de até 58,6 e 47,2%, respectivamente, enquanto que o tratamento de sementes reduziu o ID e AACPD em até 34,3 e 45,5%. Esses isolados não promoveram o crescimento do meloeiro e não produziram toxinas killer in vitro. R. aurantiaca (LMA1) e P. anomala (CC-2) foram eficazes na proteção de plântulas e plantas e no tratamento de sementes de meloeiro. Portanto, a utilização dessas leveduras junto a outros métodos de controle, tais como cultivares resistentes e utilização de compostos cúpricos, será importante no manejo integrado da mancha aquosa.

Components of the South African indigenous flora are disappearing at an alarming rate, due to pressures on land use. The flora is protected by proclamation of reserves and conservation legislation, however these measures can never be wholly successful. For these reasons, methods for propagting Clivia miniata, Gloriosa superba and Sandersonia aurantiaca using in vitro techniques were investigated. The highly sought after Clivia miniata var citrina can be successfully cultured using fruit and floral explants. Use of these explants may limit the number of plants produced in culture due to the seasonal nature of flowering. Gloriosa superba and Sandersonia aurantiaca can be propagated using corm explants, with subsequent in vitro stimulation of cormlet formation. To establish a successful tissue culture procedure an integrated approach to all aspects of the culture is necessary. Sterilization techniques should be empirical and specific for each species and explant. The most critical factor in establishing a culture technique is the choice of a suitable explant. Without a suitable explant the success of the culture procedure may be severely limited. Nutritional and environmental variation may modify the explant response in culture, but initial culture response can be directly related to the origin of the explant, particularly, size, time of the year, age and physiological status. Since the discovery of colchicine in Gloriosa by CLEWER, GREEN and TUTIN (1915) a number of researchers have put forward the idea that Gloriosa would serve as a source of colchicine. The present trend in biochemical production is via artificial synthesis, however many desirable compounds still have to be extracted from plant material for biochemical production. The utilization of plant cells that are cultured in vitro provides a viable alternative to the problems involved in the production of chemical compounds. Levels of colchicine in Gloriosa and Sandersonia are very similar, in the range of ± 0,9%. From evidence presented by BELLET and GAIGNAULT (1985), levels of colchicine in the two study species is much higher than the recorded level (0,62%) of Colchicum. This higher level of the alkaloid makes these two plants a viable source for commercial colchicine production. Levels of colchicine recovered from in vitro grown roots and callus was 10 - 20 times lower than that found in -in -viv-o tissue. Levels of colchicine extracted from plantlets grown in vitro was the same as that normally recorded for parent tissue. Higher levels of colchicine in malformed roots adds to the evidence that differentiation increases colchicine production in Gloriosa tissue in vitro. It has been shown that Gloriosa and Sandersonia tissue can synthesize colchicine in vitro. The extent to which the cells synthetic capacity can be enhanced has yet to be determined. However, research into speedier and more wide ranging methods for metabolite production in culture is receiving attention throughout the world. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1988.