References of "Wathelet, Jean-Paul"
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See detailMicrowave – assisted synthesis of carbohydrate compounds, focus on uronic acid derivatives.
Laurent, Pascal ULg; Richel, Aurore ULg; Wathelet, Bernard ULg et al

Poster (2010, May)

At the moment, biorefining is increasingly seen as a promising alternative to petrochemical sector since it targets both the replacement of part of petroleum as a source of energy and the development of ... [more ▼]

At the moment, biorefining is increasingly seen as a promising alternative to petrochemical sector since it targets both the replacement of part of petroleum as a source of energy and the development of chemicals from the biomass, such as detergents, phytopharmaceutics, solvents, plastics, etc. The valorisation of carbohydrates arising from the hydrolysis of renewable feedstocks is therefore an area of outmost interest. In this context, uronic acids such as glucuronic acid (GlcA) or galacturonic acid (GalA) derived from widely available raw material such as hemicellulose or pectins represent important biocompatible and bioresorbable starting material. The quest of highly effective, environmentally friendly and straightforward chemical strategies to transform totally O-unprotected uronic acids into high valuable materials remains actually a particularly challenging task. A new strategy enabling the quantitative “one-pot” production of water-soluble monosubstituted D-glucofuranosidurono-6,3-lactones from unprotected D-glucuronic acid (D-GlcA) involving microwaves and an inexpensive siliceous-based promoter will be described. The use of a heterogeneous acid catalytic systems consisting of sulfuric acid impregnated onto silica (H2SO4/SiG60) or onto carbon (H2SO4/C), offers a green alternative to unrecyclable liquid sulfuric acid and permit the developpment of a truly eco-friendly green process, as these supported acids were readily separated from liquid products, without neutralization, by decantation or filtration, thus minimizing energy consumption and wastes. Faced with environmental concerns, this solventless methodology offers attractive features, including short reaction times, high yields and easy set-up and workup. [less ▲]

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See detailLipase-assisted synthesis of potential bio-based surfactants starting from lignocellulosic carbohydrates
Richard, Gaetan ULg; Nott, Katherine ULg; Paquot, Michel ULg et al

Poster (2010, April)

Surfactants constitute an important class of compounds with a lot of applications, especially in the food and beverage industries (emulsion forming and stabilization, antiadhesive and antimicrobial ... [more ▼]

Surfactants constitute an important class of compounds with a lot of applications, especially in the food and beverage industries (emulsion forming and stabilization, antiadhesive and antimicrobial activities)1. With the prospect of synthesising new active compounds, white biotechnology offers efficient tools. Indeed, the use of enzymes as biocatalysts provides an interesting synthetic route in comparison to the chemical way that often requires high reaction temperatures and suffers from a lack of specificity, resulting in complex mixtures. Among all the biocatalysts available, lipases represent a class of industrial interest 2,3. In parallel, the starting material is also an important parameter : due to the depletion of petroleum reserves, its ever increasing price and various environmental aspects, the use of renewable or biomass resources is inevitable. Within the frame of a biorefinery project, we focused on the lipase-assisted modification of uronic acids. These carbohydrates can be obtained from lignocellulosic material, and, in the presence of fatty alcohols, the Candida antarctica lipase B catalyses the synthesis of amphiphilic compounds. Owing to the initial conditions used and the addition of co-solvents, we optimized the synthesis of these bio-based potential surfactants, and obtained a panel of various structures depending to the acyl acceptor used. The poster will present the details of these syntheses. [less ▲]

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See detailEffective cobalt-mediated radical coupling (CMRC) of poly(vinylacetate) and poly(N-vinylpyrrolidone) (co)polymer precursors
Debuigne, Antoine ULg; Poli, Rinaldo; De Winter, Julien et al

in Macromolecules (2010), 43(6), 2801-2813

Cobalt-mediated radical coupling (CMRC) is successfully applied to poly(vinyl acetate) (PVAc) and poly(N-vinylpyrrolidone) (PNVP) precursors for the first time. The coupling process is based on addition ... [more ▼]

Cobalt-mediated radical coupling (CMRC) is successfully applied to poly(vinyl acetate) (PVAc) and poly(N-vinylpyrrolidone) (PNVP) precursors for the first time. The coupling process is based on addition of isoprene onto polymer chains preformed by controlled radical polymerization with cobalt complexes (CMRP). The extents of coupling were high (>90%) to moderate (75-80%) for PVAc and PNVP precursors, respectively. Effects of the length of the polymer precursors and conditions used in the polymerization step on the coupling efficiency are discussed. Mass spectrometry (MS) and nuclear magnetic resonance (NMR) analyses conducted on the coupling products demonstrate the preferential insertion of two isoprene units in the final polymers. The CMRC mechanistic proposal, supported by DFT calculations, is based on this microstructure feature. Finally, illustration of the macromolecular engineering potential of this technique is given by the preparation of symmetrical PVAc-b-PNVP-b-PVAc triblock copolymers starting from the corresponding PVAc-b-PNVP-[Co] diblock copolymer. [less ▲]

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See detailThe lipoxygenase metabolic pathway in plants: potential for industrial production of natural green leaf volatiles
Gigot, Cédric ULg; Ongena, Marc ULg; Fauconnier, Marie-Laure ULg et al

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2010), 14(3), 451-460

Lipoxygenase enzymatic pathway is a widely studied mechanism in the plant kingdom. Combined actions of three enzymes: lipase, lipoxygenase (LOX) and hydroperoxide lyase (HPL) convert lipidic substrates ... [more ▼]

Lipoxygenase enzymatic pathway is a widely studied mechanism in the plant kingdom. Combined actions of three enzymes: lipase, lipoxygenase (LOX) and hydroperoxide lyase (HPL) convert lipidic substrates such as C18:2 and C18:3 fatty acids into short chain volatiles. These reactions, triggered by cell membrane disruptions, produce compounds known as Green Leaf Volatiles (GLVs) which are C6 or C9-aldehydes and alcohols. These GLVs are commonly used as flavors to confer a fresh green odor of vegetable to food products. Therefore, competitive biocatalytic productions have been developed to meet the high demand in these natural flavors. Vegetable oils, chosen for their lipidic acid profile, are converted by soybean LOX and plant HPL into natural GLVs. However this second step of the bioconversion presents low yield due to the HPL instability and the inhibition by its substrate. This paper will shortly describe the different enzymes involved in this bioconversion with regards to their chemical and enzymatic properties. Biotechnological techniques to enhance their production potentialities will be discussed along with their implication in a complete bioprocess, from the lipid substrate to the corresponding aldehydic or alcoholic flavors. [less ▲]

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See detailCobalt mediated radical coupling (CMRC) : an unusual route to midchain-functionalized symmetrical macromolecules
Debuigne, Antoine ULg; Poli, Rinaldo; De Winter, Julien et al

in Chemistry : A European Journal (2010), 16(5), 1799-1811

Cobalt-mediated radical coupling (CMRC) is a straightforward approach to the synthesis of symmetrical macromolecules that relies on the addition of 1,3-diene compounds onto polymer precursors preformed by ... [more ▼]

Cobalt-mediated radical coupling (CMRC) is a straightforward approach to the synthesis of symmetrical macromolecules that relies on the addition of 1,3-diene compounds onto polymer precursors preformed by cobalt-mediated radical polymerization (CMRP). Mechanistic features that make this process so efficient for radical polymer coupling are reported here. The mechanism was established on the basis of NMR spectroscopy and MALDI-MS analyses of the coupling product and corroborated by DFT calculations. A key feature of CMRC is the preferential insertion of two diene units in the middle of the chain of the coupling product mainly according to a trans-1,4-addition pathway. The large tolerance of CMRC towards the diene structure is demonstrated and the impact of this new coupling method on macromolecular engineering is discussed, especially for midchain functionalization of polymers. It is worth noting that the interest in CMRC goes beyond the field of polymer chemistry, since it constitutes a novel carbon-carbon bond formation method that could be applied to small organic molecules. [less ▲]

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See detailA fast gas chromatographic method for the study of semiochemical slow release formulations
Heuskin, Stéphanie ULg; Lorge, Stéphanie; Leroy, Pascal ULg et al

Poster (2010, January)

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See detailDetermination of phospholipids extracted from Tsukamurella paurometabola C-924 after freeze-drying and during the subsequent storage
Coulibaly, I.; Dauphin, R. D.; Destain, Jacqueline ULg et al

Scientific conference (2010)

The total lipids of Tsukamurella paurometabola C-924 were analyzed after freeze-drying. Seven individual lipids classes were identifiednamelyneutrallipids(NLs),fattyacids(FAs),phospholipids(PLs ... [more ▼]

The total lipids of Tsukamurella paurometabola C-924 were analyzed after freeze-drying. Seven individual lipids classes were identifiednamelyneutrallipids(NLs),fattyacids(FAs),phospholipids(PLs),sterolester(SEs),triglycerides(TGs),diglycerides (DGs) and monoglycerides (MGs). The principal fatty acids identified in most lipid classes were palmitic (C 16:0), palmitoleic (C 16:1), oleic (C 18:1), linoleic (C 18:2), and linolenic (C 18:3). PLs were the major constituents and accounted for 50-60% of the total lipids. PLs were fractionated. PLs of Tsukamurella paurometabola content phosphatidic acid (PA), phosphatidylethanolamine (PE), phosphatidylinositol (PI), phosphatidylcholine (PC), sphingomyelin (SM), lysophosphatidylcholine (LPC) and phosphatidylglycerol (PG). It was observed that PG had the highest proportion at most points relative to other PLs and was the predominant component of PLs (30%-56%). Evolution of individual rate was followed during storage at 20°C and 40°C with or without lithothamne400®, respectively. [less ▲]

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See detailThe utilization of gum tragacanth to improve the growth of Rhodotorula aurantiaca and the production of γ-decalactone in large scale
Alchihab, Mohamed ULg; Destain, Jacqueline ULg; Aguedo, Mario ULg et al

in Applied Biochemistry and Biotechnology (2010), 162(1), 233-241

The production of γ-decalactone and 4-hydroxydecanoic acid by the psychrophilic yeast R. aurantiaca was studied. The effect of both compounds on the growth of R. aurantiaca was also investigated and our ... [more ▼]

The production of γ-decalactone and 4-hydroxydecanoic acid by the psychrophilic yeast R. aurantiaca was studied. The effect of both compounds on the growth of R. aurantiaca was also investigated and our results show that γ-decalactone must be one of the limiting factors for its production. The addition of gum tragacanth to the medium at concentrations of 3 and 4 g/l seems to be an adequate strategy to enhance γ-decalactone production and to reduce its toxicity towards the cell. The production of γ-decalactone and 4- hydroxydecanoic acid was significantly higher in 20-l bioreactor than in 100-l bioreactor. By using 20 g/l of castor oil, 6.5 and 4.5 g/l of γ-decalactone were extracted after acidification at pH 2.0 and distillation at 100 °C for 45 min in 20- and 100-l bioreactors, respectively. We propose a process at industrial scale using a psychrophilic yeast to produce naturally γ-decalactone from castor oil which acts also as a detoxifying agent; moreover the process was improved by adding a natural gum. [less ▲]

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See detailL'Ylang-Ylang (Cananga odorata (Lam.) Hook & Thoms.) : une plante à huile essentielle méconnue dans une filière en danger.
Benini, Céline ULg; Danflous, J.-P.; Wathelet, Jean-Paul ULg et al

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2010), 14

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See detailEffet de la puissance micro-ondes sur la composition chimique de l'huile essentielle de l'Eucalyptus globulus
Ramdani, M.; Fadel, O.; Mouni, L. et al

Poster (2010)

Dans le but de mettre au point les conditions optimales d’extraction des huiles essentielles sous micro-ondes, nous avons effectué une série de travaux en contrôlant l’effet de plusieurs facteurs sur la ... [more ▼]

Dans le but de mettre au point les conditions optimales d’extraction des huiles essentielles sous micro-ondes, nous avons effectué une série de travaux en contrôlant l’effet de plusieurs facteurs sur la composition chimique des extraits : présence du solvant, quantité de solvant et puissance des micro-ondes. Dans le cas de l’Eucalyptus globulus récolté à Oujda, nous avons comparé la composition chimique de l’huile essentielle extraite par micro-ondes sous deux puissances différentes : 280W et 700W. 38 composés volatils ont été identifiés par GC/MS et GC/FID. La comparaison de la composition chimique, dans les deux cas de puissance d’extraction (280W et 700W), nous a permis de noter respectivement les résultats suivants : a-pinène (2,41%, 4,06%) ; transpinocarveol (2,94%, 3,28%) ; 1,8-cinéole (0,91%, 1,84%) ; (+)-aromadendrene (2,22%, 2,82) ; globulol (4,63%, 4%) ; g-eudesmol (4,66%, 4,2%) ; b-eudesmol (17,02%, 14,5%) ; 1,2,3,4-tetrahydro-2,3-methano-2,8-dimethoxynaphtalene (4,27%, 4,28%) ; anisole, p(m-chlorophenyl) (0 %, 0,24%). La puissance micro-ondes choisie a un effet direct sur la variation de la composition chimique de l’huile essentielle extraite par micro-ondes de point de vue quantitatif et qualitatif. [less ▲]

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See detailActivité antibactérienne et Technique d'extraction
Ramdani, M.; Benchat, N.; Fadel, O. et al

Poster (2010)

L’évaluation de l’activité antibactérienne fait l’objet de nombreuses études dans le domaine des plantes aromatiques et médicinales. Les résultats obtenus correspondent généralement à une technique ... [more ▼]

L’évaluation de l’activité antibactérienne fait l’objet de nombreuses études dans le domaine des plantes aromatiques et médicinales. Les résultats obtenus correspondent généralement à une technique d’extraction employée. Notre travail a pour objectif d’étudier l’effet de la technique d’extraction sur l’activité antibactérienne des huiles essentielles extraites à partir de certaines plantes aromatiques et médicinales. Nous avons préparé deux échantillons d’huiles essentielles par hydro-distillation conventionnelle et par hydro-distillation assistée par micro-ondes. Une série d’expériences a été effectuée sur un groupe de bactéries : E. coli, Staphylococcus, Klépsilla, Protéus, Bacillus. Les résultats obtenus ont montré que l’activité antibactérienne est nettement supérieur dans le cas du chauffage classique pour E. coli et Bacillus. Ceci montre que la composition chimique est différente pour les deux échantillons d’huiles essentielles. Les travaux effectués confirment que l’activité antibactérienne dépend directement de la technique d’extraction utilisée. [less ▲]

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See detailL'exraction par micro-ondes: un choix de qualité
Ramdani, M.; Ghazi, Z.; Fadel, O. et al

Poster (2010)

Le but de ce travail est de comparer l’extraction faite par chauffage classique (CC) avec celle réalisée sous micro-ondes (MO). Deux modes d’extraction ont été réalisés : - L’hydro-distillation par ... [more ▼]

Le but de ce travail est de comparer l’extraction faite par chauffage classique (CC) avec celle réalisée sous micro-ondes (MO). Deux modes d’extraction ont été réalisés : - L’hydro-distillation par chauffage classique (extraction par entraînement à la vapeur d’un solvant) et, - L’hydro-distillation activée par micro-ondes. Les MO permettent un gain de temps considérable. Par exemple, dans le cas du lavandula dentata : on note une cinétique 3 fois plus rapide, de plus le rendement est nettement supérieur (1% contre 0,6% par chauffage classique). Dans le cas de la plante fraiche, l’extraction est faite en absence de solvant sous MO. Ceci présente un grand intérêt sur le plan économique et environnemental. De plus, la qualité de l’huile extraite présente généralement une meilleure pureté. L’extraction par MO constitue une technique en accord avec la chimie verte. Grâce à ce procédé, on pourra alors réduire d'environ 60 % les besoins en énergie, ce qui diminuera d'autant les émissions de gaz à effet de serre. [less ▲]

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See detailL'organométallique au service des extraits naturels
Ramdani, R.; Ghazi, Z.; Fadel, O. et al

Poster (2010)

Le Maroc est considéré parmi les pays méditerranéens les plus riches en ressources naturelles, notamment, les plantes aromatiques et médicinales. La valorisation des extraits naturels passe soit par des ... [more ▼]

Le Maroc est considéré parmi les pays méditerranéens les plus riches en ressources naturelles, notamment, les plantes aromatiques et médicinales. La valorisation des extraits naturels passe soit par des échantillons à l’état brut, soit en les transformant en d’autres structures chimiques nouvelles. [less ▲]

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See detailChemical Composition and Antimicrobial Activity of the Essential Oil of Myrtus communis L. from Algeria
Brada, M.; Hennia, A.; Nemmiche, S. et al

Poster (2010)

This study deals with the valorisation of medicinal and aromatic plants of the Algerian flora, in order to find new bioactive natural products. Myrtus communis essential oil obtained by hydrodistillation ... [more ▼]

This study deals with the valorisation of medicinal and aromatic plants of the Algerian flora, in order to find new bioactive natural products. Myrtus communis essential oil obtained by hydrodistillation was investigated by capillary gas chromatography and gas chromatography/mass spectrometry. Twenty-seven volatile compounds were identified in the leaves essential oil; the major components were: -pinene (23.5 %), limonene (22.9 %), 1,8-cineole (16.1 %), linalool (13.0%), linalyl acetate (10.9%) and geranyl acetate (4.6%). The antibacterial activity of essential oils extracts was evaluated by the diffusion method and by the dilution method in liquid medium on pathogenic bacteria (Staphylococcus aureus, Escherichia coli, Salmonella sp, Proteus sp and Klebsiella sp). [less ▲]

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See detailInteraction between earthworms and soil fungi: volatiles attraction
Zirbes, Lara ULg; Thonart, Philippe ULg; Wathelet, Jean-Paul ULg et al

in 9th International Symposium on Earthworm Ecology (2010)

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See detailChemical Composition, Cytotoxic and Antioxydant Activity of The Essential Oil of Lavandula dentata
Imelouane, B.; El Bachiri, A.; Wathelet, Jean-Paul ULg et al

in World Journal of Chemistry (2010), 5(2), 103-110

The composiiton of the essential oil from aerial part and flowers of lavandula dentate, collected in eastern Morocco (Taforalt, Talazart), were analysed by GC/FID and GC-MS.

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