Isobutylamine N-hydroxylase (IBAH) and flavin reductase (FRED) from Streptomyces viridifaciens are part of a two-component flavin-dependent monooxygenase enzyme system that catalyze the conversion of isobutylamine (IBA) to isobutylhydroxylamine (IBHA), a key step in the formation of valanimycin, an azoxy antibiotic. In this work, we present the over-expression, purification and biochemical characterization of this two-component enzyme system. IBAH and FRED were expressed and purified to homogeneity as separate proteins. FRED exhibited the oxidoreductase activity by catalyzing the oxidation of NADPH. The hydroxylation activity of IBAH was confirmed using liquid chromatography – mass spectrometry (LC-MS). Steady state kinetic data showed an oxidation activity of the monooxygenase component which proceeded at 1.97 ± 0.06 s⁻¹ as measured from oxygen consumption and in product formation, the rate was 0.012 ± 0.001 s⁻¹ , suggesting a high degree of uncoupling between product formation and oxygen consumption. In pre-steady state kinetic characterization studies, the FRED-catalyzed reduction of FAD by NADPH occurred at a rate of 10.0 ± 0.2 s⁻¹ and the KM was 490 ± 40 µM. The rate of reduction was ~1.5-fold decreased in the presence of substrate IBA whiles the KM was 500 ± 50 µM. NADH showed a markedly reduced rate of reduction with a kred of 0.34 ± 0.03 s⁻¹ with an apparent KM of 3000 ± 500 µM. The rate of flavin re-oxidation in the absence of monooxygenase IBAH was 4.79 × 10⁻⁹ M-1 s⁻¹. Our results suggest a reaction mechanism for the IBAH monooxygenase system controlled by the oxidation half reaction that may be modulated by a complex formation between the reductase and monooxygenase components. / Master of Science in Life Sciences

Thesis (PhD)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Sulfated galactans (agarans and carrageenans) are accumulated in the cell wall of various red algae (Rhodophyta) species. These polysaccharides are of commercial importance in the food, pharmaceutical and biotechnology industries due to their unique physicochemical properties. Although having received significant research attention over the last 20 years, events regarding their biosynthesis have not been elucidated. Aiming for the identification of galactosyltransferase (GalT) genes involved in sulfated galactan biosynthesis, cDNA expression libraries were constructed from the prolific agar-producing South African red seaweed Gelidium pristoides (Turner) Kützing and screened by functional complementation of UDP-galactose 4-epimerase deficient mutants (E. coli and S. cerevisiae). Regretfully, no GalTs were identified. The study however yielded the first UGE enzyme described for a red seaweed. Southern hybridization indicated the presence of two UGE copies and confirmed the gene originated from G. pristoides. Bioinformatic analysis of G. pristoides UGE shows amino acid sequence homology to known UGEs from various organisms. The enzyme was shown to be functional in E. coli crude extracts and showed affinity for UDP-D-galactose, similar to other UDP-galactose 4-epimerases. Further, the isolated G. pristoides UGE (GpUGE) was biochemically characterized and its kinetic parameters determined. We found that there was no kinetic difference between this enzyme and previously described UGE enzymes except enhanced activity in the presence of exogenously added NAD+. The UDP-galactose 4-epimerase (UDP-glucose 4-epimerase, UGE, EC 5.1.3.2) is an essential Leloir pathway enzyme facilitating the catalytic inter-conversion between UDP-D-glucose and UDP-D-galactose. UDP-D-galactose is the nucleotide sugar required by galactosyltransferases for the production of red algae sulfated galactans. UGE is suspected as being responsible for supplying UDP-D-galactose for the synthesis of sulfated galactans. In planta monitoring of GpUGE transcript levels with respect to dark and light cycling indicated high expression of the enzyme at night, while expression diminished during the day. The occurrence of increased nocturnal UGE expression correlates with floridean starch breakdown at night. Evidence for hydrolysis of floridean starch is also reflected in obtained G. pristoides transcriptome sequence data. In red algae, floridean starch degradation coincides with sulfated galactan production. The detection of starch hydrolysis enzyme transcripts alongside increased expression of GpUGE suggests the enzyme plays a role in supplying UDP-Dgalactose for sulfated galactan production. As far as we know, this the first report of sequencing and biochemical characterization of a UGE from red seaweed.

Lactic acid bacteria have been reported to be used as a health adjunct in food for u many years. However, these health benefits have not been proven. and how these bacteria pass through the digestion process and remain viable in the human intestinal tract is still not clear. The aim of this work was to isolate mutants from Lactobacillus acidophilus or Bifidobacterium bifidum that could tolerate the conditions of the digestion process (low pH and bile conduction) and to characterize these isolated mutants. Acid- and bile-tolerant mutants of L. acidophilus were isolated from parental strains successfully using natural selection techniques. These mutants survived and grew at conditions of pH 3.5 with 0.2% mixed bile salts added. After the selection, phenotypic characterization was identified to further clarify desirable traits for use as probiotic adjuncts in foods. These phenotypic characteristics included protease, aminopeptidase, ß-galactosidase, and bile salt hydrolase activity. Based on different protease, aminopeptidase, and ß-galactosidase activity, selected acid- and bile-tolerant mutants contained different growth characteristics compared with their parents. All the isolates tested showed different bile salt hydrolase activity, and this activity was not strain and medium dependent. Plasmid profiles and fatty acid analysis were conducted to provide more information of these acid/bile tolerant isolates and whether or not they were mutants from their parent strains rather than only adapted variants. Results showed the acid-/bile-tolerant isolates contained different plasmid profiles and cell wall fatty acids compared with their parents, which indicated these isolates were mutants. Protein expression by two-dimensional gel electrophoresis showed different protein expression patterns between acid- and bile-tolerant mutants and their parents. fm1her suggesting these isolates were mutants. We observed the protein production in parent strains decreased as the pH decreased. and protein expression in mutants remained the same as pH decreased. Two of the proposed health benefits of probiotic bacteria are anticholesterol activity and antimicrobial activity. These were evaluated using selected acid- and bile-tolerant mutants. Results showed no decrease of cholesterol in the test medium during bacterial growth. The observed antimicrobial activity was due to the presence of active cells. and this may relate to the acid production during cell growth and not to the production of antimicrobial substances. We concluded that the acid-/bile-tolerant isolates were mutants, and they survived and grew better in harsh environments compared with their parent strains. These mutants may be useful as a food adjunct in the future, but further study is needed to establish their use and possible probiotic benefits.

The family of Deg/HtrA proteases is present in a wide range of organisms from bacteria, archaea to eukaryota. These ATP-independent serine endopeptidases play key roles in the cellular protein quality control. The cyanobacterium Synechocystis sp. PCC 6803, a model organism for studies on photosynthesis, metabolism and renewable energy, contains three Deg proteases known as HhoA, HhoB and HtrA. The three proteases are important for survival in stress conditions, such as high light or temperature. In my work the biochemical characteristics of each protease were revealed in vitro and in vivo. In vitro studies performed using recombinant Synechocystis Deg proteases allowed conclusions about their oligomerization states, proteolytic activities and tertiary structure. The in vivo studies addressed their sub-cellular localization, expression and physiological importance by comparing wild-type Synechocystis cells with the three single mutants lacking one of the Deg proteases. HhoA seems to be involved in the cytoplasmic protein quality control. This protease is regulated post-transcriptional and post-translational: oligomerization, pH and/or cation-binding are some of the important factors to stimulate its proteolytic activity. Instead HhoB acts on periplasmic proteins and seems to be important for the transportation/secretion of proteins. While it has low proteolytic capacity, it may act as a chaperone. The stress-induced HtrA functions in the cellular tolerance against photosynthetic stress; additionally it might act as a protease partner of HhoB, generating a protease/chaperone complex. The results presented in this thesis lay the foundation for a better understanding of the dynamic protein quality control in cyanobacteria, which is undoubtedly important for various cellular metabolic pathways.

Polyphenol oxidases are enzymes that catalyze the oxidation of certain phenolic substrates to quinones in the presence of molecular oxygen. Polyphenol oxidases are widely used in several applications. In food industry, they are used for enhancement of flavor in coffee, tea and cocoa production, and determination of food quality. In medicine, they have several uses in treatments of Parkinson&rsquo / s disease, phenlyketonurea and leukemia. In wastewater treatment, they are used for the removal of phenolic pollutants from wastewaters. In pharmaceutical industry, differentiation of morphine from codeine is possible by means of polyphenol oxidase immobilized electrodes. In this study, a thermophilic fungus, Thermomyces lanuginosus was evaluated in terms of poyphenol oxidase production. The effect of different nutrient sources, inducers and fermentation parameters on enzyme production were investigated and maximum PPO activity of 97 U/ml was observed in bioreactor experiments at 50&deg / C, 400 rpm and pH 8.0 in a fermentation medium containing 1.4% yeast extract, 0.3% MgSO4, 1% KH2PO4, 0.003% CuSO4, 0.032% gallic acid. Type of polyphenol oxidase produced by Thermomyces lanuginosus was determined as laccase. For biochemical characterization studies, the enzyme was enriched by electrophoresis. Temperature and pH optima for the enzyme were determined as 60&deg / C and 8.0, respectively. Enzyme retained 67% activity after 1 h incubation at 80&deg / C and retained 87% of its activity after 1 hour of incubation at pH 9.0 at room temperature. The enzyme obeys Michealis-Menten kinetics with Km and Vmax values being 5 mg /ml catechol and 38 U/ml, respectively. Molecular weight of the enzyme was determined as 29 kDa and isoelectric point of enzyme was found to be approximately 6.0.

In this study, the aim was to find an economical plant source for polyphenol oxidase (PPO) production as an alternative to mushroom and possible application areas by characterization and immobilization of the PPOs. For this purpose, tissues of various plants of no commercial value were screened for their PPO activities. Mulberry leaf tissues showed the highest PPO activity against 4-methyl catechol which was comparable to that of mushroom. Average Km and Vmax values of free mulberry leaf PPOs were found as 7 mM and 218 U/ml, respectively. Mulberry leaf PPOs were immobilized in a polypyrole matrix and the Km and Vmax values of immobilized PPOs were calculated as 35 mM and 3 U/ml, respectively. Mulberry leaf PPO was the most active at 45&deg / C and pH 7. By using electrophoretic analysis, laccase and catechol oxidase type activities of PPOs and in addition, peroxidase activity were detected. Molecular weights of laccase, peroxidase and catechol oxidase were found to be about 62, 64 and 62-64 kDa, with pI values of 8.0-8.5, 4.5 and 10, sequentially.

La protéine « Selenium Binding Protein » (SBP1), présente chez la plupart des êtres vivants, a un rôle qui n'est pas encore élucidé. Cette protéine possède dans sa structure primaire de nombreux sites potentiels de liaisons aux métaux. Chez Arabidopsis thaliana, la surexpression de SBP1 augmente la tolérance à deux composés toxiques pour la plante, le cadmium (Cd) et le sélénium (Se) qui sont présents dans les sols pollués. Pour mieux comprendre la fonction de SBP1 dans les mécanismes de détoxication, une démarche intégrée combinant deux approches complémentaires, in vitro et in planta, a été menée. La caractérisation biochimique de SBP1 a mis en évidence ses propriétés chélatrices vis-à-vis de différents ligands dont le Cd et le Se. Le Cd se lie à SBP1 avec un ratio molaire ligand/SBP1 de 3 et un KD de 2,2 × 10-7 M via principalement des acides aminés soufrés et potentiellement à moindre échelle des résidus histidines. Le Se, initialement sous forme SeO32-, se lie à SBP1 de façon covalente, avec un ratio molaire ligand/SBP1 de 1, via les cystéines 21 et 22 pour former une liaison de type R-S-Se-S-R. Les analyses in planta de localisation subcellulaire ont montré que SBP1 était à la fois cytosolique et nucléaire. L'utilisation de lignées bioluminescentes a permis d'analyser la zone promotrice du gène SBP1. Le motif cis ‘GAGAC' connu pour être impliqué dans la régulation de certains gènes à une carence en soufre (S) a été identifié comme élément cis majeur de la régulation de l'expression de SBP1 en réponse à différents stress, dont le Cd et le Se. Ce résultat démontre l'existence d'un lien entre la fonction de SBP1 et une demande en S de la cellule. La surexpression de SBP1 in planta perturbe le niveau d'accumulation du Se dans les parties aériennes, mais pas sa spéciation. L'ensemble de ces résultats semble indiquer que SBP1 soit impliquée dans des mécanismes de détoxication via ses propriétés chélatrices et qu'elle joue également un rôle dans le métabolisme du S et du Se. / The function of the protein “Selenium binding protein 1” (SBPP1), present in almost all organisms, is not yet well established. This protein has numerous potential metal binding sites. In Arabidopsis thaliana, SBP1 overexpression increases tolerance to two toxic compounds for the plant, cadmium (Cd) and selenium (Se), which are often found as soil pollutants. For a better understanding of SBP1 function and its involvement in detoxification mechanisms, an integrated approach combining in vitro and in planta experiments, has been performed. Biochemical characterization of SBP1 has revealed its chelating properties to different ligands including Cd and Se. Cd is bound to SBP1 with a metal ion to protein molar ratio of 3 and a KD of 2.2 × 10-7 M mainly via sulfur-containing amino acids and potentially histidine residues. Se from SeO32- can covalently bound SBP1 with a ligand to protein molar ratio of 1. This binding occurs via cysteines 21 and 22 and forms a R-S-Se-S-R complex. In planta analyses have shown that SBP1 is cytosolic and nuclear. The use of bioluminescent lines allowed the identification of a GAGAC motif in the SBP1 promoter region. This motif is a sulfur starvation responsive element and a major cis element involved in SBP1 expression in response to stress, including Cd and Se. The result directly links SBP1 function to an enhanced sulfur demand of the cell. SBP1 over expression in plants disturbs Se accumulation in shoots but not its speciation. All together these results strongly suggested that SBP1 could act as a detoxifying protein through its chelating properties and plays a role in S/Se metabolisms.

Dissertação(mestrado) - Universidade Federal do Rio Grande, Programa de Pós-Graduação em Engenharia e Ciência de Alimentos, Escola de Química e Alimentos, 2010. / Submitted by Caroline Silva (krol_bilhar@hotmail.com) on 2012-08-19T20:54:12Z No. of bitstreams: 1 dissertao -fernanda pagnussatt.pdf: 1418590 bytes, checksum: 8967b30d06e7a8e26859db843f84ec54 (MD5) / Approved for entry into archive by Bruna Vieira(bruninha_vieira@ibest.com.br) on 2012-12-06T18:47:43Z (GMT) No. of bitstreams: 1 dissertao -fernanda pagnussatt.pdf: 1418590 bytes, checksum: 8967b30d06e7a8e26859db843f84ec54 (MD5) / Made available in DSpace on 2012-12-06T18:47:43Z (GMT). No. of bitstreams: 1 dissertao -fernanda pagnussatt.pdf: 1418590 bytes, checksum: 8967b30d06e7a8e26859db843f84ec54 (MD5) Previous issue date: 2010 / Os cereais são fontes de inibidores enzimáticos que agem sobre a α-amilase, alterando a disponibilidade do amido e podem representar uma ferramenta útil para a resistência dos vegetais ao ataque de patógenos. O objetivo do trabalho foi estudar a presença de inibidores enzimáticos em cereais e avaliar sua relação com a susceptibilidade à contaminação fúngica. Amostras de grãos de aveia (UPFA 20 Teixeirinha, UPFA 22 Temprana e UPFA Pampa), trigo (Safira, Ônix e Pampeano) e arroz (BR 410, BR 417 e BR 424) foram moídas,peneiradas e caracterizadas físico-quimicamente. A melhor condição para a extração de inibidores enzimáticos da aveia e trigo foi obtida ao utilizar o sistema de extração etanol 70 % e 12 horas de agitação, com inibição da amilase fúngica em torno de 90 %. Nas cultivares de arroz, o extrato bruto inibiu 96 % da ação da enzima amilase em ensaios in vitro, quando se empregou como extrator etanol 95 % e 7 h de extração. A enzima Fungamyl®, com atividade específica de 20 mg de amido hidrolisado mL-1 mg proteína-1 foi caracterizada bioquimicamente para fornecer os parâmetros necessários para avaliação da presença de inibidores nos extratos. As propriedades antifúngicas desses extratos inibidores foram testadas pelo método de ágar diluído, utilizando como resposta o teor de glucosamina dos fungos. Durante os 14 dias de incubação do Fusarium graminearum as maiores inibições de crescimento fúngico foram alcançadas em presença dos extratos de aveia e de trigo. A próxima etapa será a purificação dos inibidores nas cultivares mais promissoras para aplicar o conhecimento em programas genéticos capazes de aumentar a resistência desses grãos a determinados fungos ou extraí-los para a preservação em conservação de alimentos. / Cereals are sources of enzymatic inhibitors which act upon alpha-amylase disturbing starch availability, generating a higher resistance to the attack of pathogens. This work aim was to study the presence of enzymatic inhibitors in cereals and evaluate its relation with fungi contamination susceptibility. Samples of oat (UPFA 20 Teixeirinha, UPFA 22 Temprana e UPFA Pampa), wheat (Safira, Ônix e Pampeano) and rice (BR 410, BR 417 e BR 424) were milled, homogenized and then its physicochemical properties were analyzed. The best conditions for extraction enzymatic inhibitors of wheat and oat was ethanol 70%, 12 hours of agitation which obtained an inhibition of fungal amylase of 90%. Rice crude extract varieties obtained a 96% of enzymatic amylase inhibition during in vitro tests, when extraction contained 95% of ethanol and 7 h agitation. The enzyme Fungamyl®, which specific activity of 20 mg protein mL-1 mg-1 of hydrolyzed starch, was biochemically characterized to establish the necessary parameters to research inhibitors activity. Antifungal properties from the extracts were analyzed utilizing the diluted agar method, the response was measure through the level of glucosamine produce by the fungi. During 14 days of incubation Fusarium graminearum inhibition was greater in the oat and wheat extracts presence. The next stage it’s to purify of the inhibitors on the cultivars most promising to apply this knowledge to genetic databases that are capable to enhance the resistence of grains to certain species of fungi or extract them for preservation in foods.

Orientador: Glaucia Maria Pastore / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-12T17:24:09Z (GMT). No. of bitstreams: 1 Silva_JunioCota_M.pdf: 1041148 bytes, checksum: 4cc2da3de714f40ac19aea72962747ef (MD5) Previous issue date: 2009 / Abstract: Impulsionados pela grande demanda por alimentos ¿saudáveis¿ e de calorias controladas, têm surgido desde os anos 80 um grande número de adoçantes alternativos e, entre eles, diversos oligossacarídeos. Entre os oligossacarídeos mais estudados estão os frutooligossacarídeos (FOS), que se tornaram mais importantes por suas propriedades funcionais que pelo seu poder adoçante. Os FOS podem ser produzidos por meio da reação de transfrutosilação catalisada pela enzima frutosiltransferase (FTase), onde uma molécula de sacarose é hidrolisada e o radical frutosil é transferido para outra sacarose. Diversos microrganismos possuem o gene que codifica para a FTase, e sua aplicação industrial já está bem estabelecida, contudo, o Brasil detém apenas uma pequena fração do total de patentes desses processos tecnológicos. Esse trabalho teve por objetivo selecionar novas linhagens microbianas produtoras de frutosiltransferase que sejam eficientes e competitivas com as já descritas na literatura. Para isso, novas linhagens de microrganismos foram isoladas do Baru, um fruto do cerrado. Inicialmente 54 linhagens foram avaliadas quanto à atividade de transfrutosilação, sendo identificadas 13 como potenciais produtoras de FTase. Cada uma das 13 linhagens foi testada com relação à síntese de FOS em diferentes tempos de reação (6, 12, 24, 48 e 72 h), tendo sido utilizadas preparações enzimáticas parcialmente purificadas. A FTase de Penicillium sp. apresentou o maior rendimento da reação de síntese de FOS (50%), sendo as condições de reação 500g.L-1 de sacarose, 20% de enzima (v/v), agitação de 100 rpm, temperatura de 50°C e tempo de reação de 48 horas, em tampão acetato 50 mM (pH 4,5). Baseando-se no rendimento da reação de síntese de FOS, essa linhagem de Penicillium sp. foi selecionada para realização de estudos dos parâmetros cinéticos e termodinâmicos da FTase. Foi utilizada a metodologia de superfície de resposta para avaliar as condições ótimas de atividade enzimática, sendo estas: pH de 4,8 a 5,2, 54 a 57°C e sacarose (410 a 520 g.L-1). Os parâmetros termodinâmicos tempo de meia vida (t1/2), constante de desnaturação (kd) e valor de redução decimal (D) foram determinados para cada uma das quatro temperaturas estudadas (45, 50, 55 e 60°C). A energia de ativação da desnaturação (Ead) e o valor z também foram calculados para a FTase. A enzima estudada apresentou inibição pelo substrato quando a concentração de sacarose foi superior a 400 g/L. Os parâmetros cinéticos vmax, km e ki foram estimados pelos métodos de linearização de Lineweaver-Burk e Eadie-Hofsteen e pelo modelo de clássico de inibição combinado com o modelo de Hill utilizando o software Statistica® 8.0. A análise das constantes sugere que há um fenômeno de inibição que afeta a enzima e não foi possível a identificação de quais componentes do sistema reacional causam a inibição enzimática, utilizando apenas o modelo clássico de inibição, sendo necessários estudos futuros para desenvolver o modelo cinético adequado para a FTase. Os resultados obtidos indicam que a FTase de Penicillium sp. tem potencial para ser aplicada em processos industriais para produção de FOS / Abstract: Nowadays, there is a high demand on health and low caloric food. Since the years of 1980 a big number of sweteners have appeared to replace sucrose. The fructooligosacchrides (FOS) are considered the most important sweeteners among them due their properties to promoting health by increasing of the amount of beneficial bacteria in human gut. They can be produced by simple transfructosilation reaction catalysed by fructosyltransferase (FTase), wherein one molecule of sucrose is hydrolyzed and the fructosyl radical is bonded to another sucrose. Some microorganisms have the gene encoding FTase and its industrial applications are well known. However, Brazil has a small share of patents registered around the world in these technological process. In this work, we aimed to find potential microorganisms strains that produce both FTase and FOS. New strains were isolated from Baru fruits of Brazilian Cerrado biome. Initially 54 isolated strains were screened for transfructosilating activity. As result it was found 13 strains which were able to produce FTase. Enzimatc extracts partially purified from each of 13 strains were evaluated in the ability to produce FOS in several reaction times (6, 12, 24, 48 and 72 h). The reaction conditions were 500 g.L-1 sucrose, 20% (v/v) enzime:solution, 100 rpm, 50°C and 48 h reaction time in acetate buffer 50 mM (pH 4,5). The Penicillium sp. FTase showed the highest yield of FOS synthesis. Hence this strain was selected to study the FTase kinetical and thermodynamical properties. The best conditions found using the Response Surface Methodology were: pH 4.8 to 5.2; 54 to 57°C and 410 to 520 g.L-1 sucrose. The thermodynamic parameters half-life (t1/2), denaturation constant (kd) and the decimal reduction time (D) were calculated to each of the four tested temperatures (45, 50, 55 e 60°C). The activation energy of denaturation (Ead) and the z-value were also calculated. This enzyme showed inhibition by substrate when the sucrose concentration was above 400 g.L-1. The kinetical parameters vmax, km e ki were estimated by Lineweaver-Burk e Eadie-Hofsteen linearization methods. In addition, these constants were also estimated by classic model of inhibition combined with the Hill model using the StatisticaTM 8.0 software. The data analisys indicated an enzimatic inhibition fenomena. However, it was not possible to identify which agents triggered the enzimatic inhibition using only the classic model. It is necessary more future studies to elucidate the appropriated model to FTase. These results sugest that the FTase from Penicillium sp. has a great potential to be applied in further FOS industrial processes / Mestrado / Mestre em Ciência de Alimentos

Le baobab est un arbre qui pousse à l'état sauvage en Afrique et ailleurs dans le monde où le fruit est consommé sous différentes formes. Si l'écologie et la botanique de la plante ont été bien étudiées, il y a peu d'information disponible sur la composition biochimique d'une manière générale et même inexistante chez les espèces malgaches en particulier. Cette étude s'inscrit dans le contexte du développement et de la valorisation des produits locaux en Afrique. Elle a pour objectif principal de mieux caractériser la pulpe des fruits de baobabs issus d'échantillons de diverses provenances de Madagascar et d'Afrique. A cette fin, elle s'est attachée dans un premier temps à caractériser et à quantifier les principaux éléments nutritifs comme les glucides, les acides aminés, les lipides, les polyphénols, la vitamine C, les acides organiques, les éléments minéraux et les arômes. La caractérisation biochimique de la pulpe a révélé une forte acidité titrable (102 meq/100g) et une teneur élevée en acide ascorbique (jusqu'à 312 mg/100g) et en polyphénols de (60,24 à 137,81mg/100g et de 329 à 1705,98 mg/100g) ainsi qu'un potentiel antioxydant très fort et une bonne source de Ca 658 mg/100g.Une évaluation du potentiel de ce fruit pour une valorisation à plus grande échelle à travers une amélioration des procédés de transformation existant en Afrique a été réalisée. L'identification d'une approche de stabilisation et de conservation du nectar par voie conventionnelle (pasteurisation) a été réalisée. Nos résultats ont montré que le nectar est aussi nutritif que les fruits usuels et que sa stabilisation peut se faire par une pasteurisation en utilisant le barème 70°C/10 min. L'analyse sensorielle du nectar après chaque étape de traitement ou de conservation (42 j) n'a pas montré de modification organoleptique du produit quelque soit la température de stockage Deux approches empiriques classiques (modèles d'Arrhenius et de Ball) ont été utilisés pour décrire la cinétique de dégradation thermique de la vitamine C du nectar.Enfin, une étude de faisabilité de l'utilisation de la spectrométrie proche infrarouge pour la caractérisation des origines et pour la détermination des teneurs en constituants biochimiques a été réalisée. Ce travail a permis de montrer qu'il était possible de doser la matière sèche, les protéines, le fructose et le potassium.Une séparation des espèces basée sur l'analyse des spectres semble aussi pouvoir être réalisée via leur appartenance aux sections (brevetubae, longitubae). / Baobab tree is growing wild in Africa and elsewhere in the world. Fruits are consuming in different ways. Plant ecology and botanic are well detailed, but generally few information is available on biochemical composition and even nothing about Malachi species. This study takes place in the development and valorization of African local fruits program. The main objective is to characterize baobab fruit pulp samples coming from both Madagascar and Africa. First, the main nutriments were characterized and quantified, such as, carbohydrates, amino acids, lipids, polyphenols, vitamin C, organic acids, minerals and aroma compounds. Biochemical characterization of the pulp showed high level of total acidity (102 meq/100g), ascorbic acid (till 312 mg/100g), polyphenols (from 60.24 to 137.81mg/100g) and anti oxidant potential.To valorize the fruit at larger scale, evaluation of its potential was realized trough improvements of existing processing techniques in Africa. A conventional approach (pasteurization) was realized to stabilize and store nectar. Data show nectar is as nutritive than fresh fruit with pasteurization schedule at 70°C/10min. Sensory analysis of nectar after each step of process doesn't show organoleptic difference relative to storage temperature. Two classical empirical approaches (Arrhenius and Ball models) were used to describe kinetic of thermal degradation of C vitamin of nectar.At least, Near Infra Red Spectroscopy (NIRS) was tested, to determine geographical origins and levels of biochemical compounds. Dry matter, proteins, fructose and potassium were quantified. Species segregation with NIRS seems possible by means of belonging to brevetubae and longitubae sections.