References of "Thonart, Philippe"
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See detailStructural and functional organization of the fengycin synthetase multienzyme system from Bacillus subtilis b213 and A1/3
Steller, S.; Vollenbroich, D.; Leenders, F. et al

in Chemistry & Biology (1999), 6(31-41),

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See detailConversion of green note aldehydes into alcohols by yeast alcohol dehydrogenase
Fauconnier, Marie-Laure ULg; Mpambara, A.; Delcarte, Jérôme et al

in Biotechnology Letters (1999), 21(7), 629-633

‘Green note’ aldehydes were successfully reduced into their corresponding alcohol by commercial yeast alcohol dehydrogenase. Among different yeasts tested for their ability to convert (Z)-3-hexenal into ... [more ▼]

‘Green note’ aldehydes were successfully reduced into their corresponding alcohol by commercial yeast alcohol dehydrogenase. Among different yeasts tested for their ability to convert (Z)-3-hexenal into (Z)-3-hexenol, Pichia anomala gave the best results. Conversion yields higher than 90% were also obtained by directly conducting the reaction in the medium where (Z)-3-hexenal is produced by the action of lipoxygenase and hydroperoxide lyase on <br />linolenic acid. [less ▲]

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See detailComputer Simulation Of Surfactin Conformation At A Hydrophobic/Hydrophilic Interface
Gallet, X.; Deleu, Magali ULg; Razafindralambo, Hary ULg et al

in Langmuir (1999), 15(7), 2409-13

Using a molecular modeling method, different conformations of surfactin at a hydrophobic/hydrophilic interface are established. Two conformations of the peptide ring (S1 and S2) provided by NMR ... [more ▼]

Using a molecular modeling method, different conformations of surfactin at a hydrophobic/hydrophilic interface are established. Two conformations of the peptide ring (S1 and S2) provided by NMR experiments built with three different aliphatic chains in folded or extended configurations were studied. For the structures including the S2 peptide ring conformation, the theoretical interfacial molecular area corresponds to the experimental limiting area A0 value obtained with a Langmuir film balance. The peptide ring is positioned in the plane of the interface with the two acidic chains close to each other and protruding in the aqueous phase, and the β-hydroxy fatty acid chain, folded to interact mainly with the Leu2 side chain and also with the Val4 side chain. This design has the largest calculated molecular area and would correspond to the most stable amphipathic structure representing the surfactin experimental behavior in weak compression. [less ▲]

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See detailIn vitro root cultures of Panax ginseng and P-quinquefolium
Kevers, Claire ULg; Jacques, Philippe ULg; Thonart, Philippe ULg et al

in Plant Growth Regulation (1999), 27(3), 173-178

The paper describes a procedure for the initiation, subculture and continued proliferation of adventitious roots of Panax ginseng and Panax quinquefolium, which resemble hairy roots. The technique took ... [more ▼]

The paper describes a procedure for the initiation, subculture and continued proliferation of adventitious roots of Panax ginseng and Panax quinquefolium, which resemble hairy roots. The technique took advantage of the high powerful activity of a new synthetic auxin: benzo[b]selenienyl acetic acid (BSAA). Such initiation from root explants was dependent upon the season, the type and concentration of auxin. The hairy-like roots of ginseng could be subcultured by transfer every 4 weeks to fresh liquid medium either in agitated Erlenmeyer flasks or in bioreactors. Optimal conditions for a continued multiplication (up to 14 per month) were determined. The only practical problem was the limitation of the fresh mass as inoculum: the multiplication rate decreased with the increased quantity of roots. It is postulated that a root growth inhibiting substance was released into the media by the proliferating ginseng hairy roots. [less ▲]

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See detailThe structure of two fengycins from Bacillus subtilis S499.
Schneider, J.; Taraz, K.; Budzikiewicz, H. et al

in Zeitschrift für Naturforschung. C, Journal of Biosciences (1999), 54(11), 859-66

The structures of the two fengycins, lipopeptides from Bacillus subtilis, were elucidated by spectroscopic methods and chemical degradation. They show a close structural relationship to the plipastatins ... [more ▼]

The structures of the two fengycins, lipopeptides from Bacillus subtilis, were elucidated by spectroscopic methods and chemical degradation. They show a close structural relationship to the plipastatins from Bacillus cereus differing only in the stereochemistry of the Tyr residues. [less ▲]

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See detailNanometer scale organization of mixed surfactin/phosphatidylcholine monolayers
Deleu, Magali ULg; Paquot, Michel ULg; Jacques, Philippe ULg et al

in Biophysical Journal (1999), 77(4), 2304-2310

Mixed monolayers of the surface-active lipopeptide surfactin-C-15 and of dipalmitoyl phosphatidylcholine (DPPC) were deposited on mica and their nanometer scale organization was investigated using atomic ... [more ▼]

Mixed monolayers of the surface-active lipopeptide surfactin-C-15 and of dipalmitoyl phosphatidylcholine (DPPC) were deposited on mica and their nanometer scale organization was investigated using atomic force microscopy (AFM) and x-ray photoelectron spectroscopy (XPS). AFM topographic images revealed phase separation for mixed monolayers prepared at 0.1, 0.25, and 0.5 surfactin molar ratios. This was in agreement with the monolayer properties at the air-water interface indicating a tendency of the two compounds to form bidimensional domains in the mixed systems. The step height measured between the surfactin and the DPPC domains was 1.2 +/- 0.1 nm, pointing to a difference in molecular orientation: while DPPC had a vertical orientation, the large peptide ring of surfactin was lying on the mica surface. The N/C atom concentration ratios obtained by XPS for pure monolayers were compatible with two distinct geometric models: a random layer for surfactin and for DPPC, a layer of vertically-oriented molecules in which the polar headgroups are in contact with mica. XPS data for mixed systems were accounted for by a combination of the two pure monolayers, considering respective surface coverages that were in excellent agreement with those measured by AFM. These results illustrate the complementarity of AFM and XPS to directly probe the molecular organization of multicomponent monolayers. [less ▲]

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See detailInterfacial and emulsifying properties of lipopeptides from Bacillus subtilis
Deleu, Magali ULg; Razafindralambo, Hary ULg; Popineau, Y. et al

in Colloids and Surfaces A : Physicochemical and Engineering Aspects (1999), 152(1-2), 3-10

The fundamental surface-active properties at the oil/water interface and emulsifying properties of surfactin, iturin A and fengycin, lipopeptides from Bacillus subtilis, were investigated. All ... [more ▼]

The fundamental surface-active properties at the oil/water interface and emulsifying properties of surfactin, iturin A and fengycin, lipopeptides from Bacillus subtilis, were investigated. All lipopeptides reduce rapidly the dynamic interfacial tension. Among lipopeptide families, surfactin is the most effective in terms of fundamental dynamic and equilibrium interfacial properties. Lipopeptides present intermediate properties in comparison with sodium dodecyl sulfate and beta-lactoglobulin concerning the stabilizing effect towards creaming-flocculation and the resistance to coalescence. Among lipopeptides, iturin A seems to show the best resistance to creaming-flocculation whereas fengycin exhibits the highest resistance to coalescence properties. (C) 1999 Elsevier Science B.V. All rights reserved. [less ▲]

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See detailImproving The Catabolic Functions Of Desiccation-Tolerant Soil Bacteria
Weekers, F.; Jacques, Philippe ULg; Springael, D. et al

in Applied Biochemistry and Biotechnology (1999), 77-9

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See detailOptimization of biosurfactant lipopeptide production from Bacillus subtilis S499 by Plackett-Burman design
Jacques, Philippe ULg; Hbid, C.; Destain, Jacqueline ULg et al

in Applied Biochemistry and Biotechnology (1999), 77-9

Bacillus subtilis S499 is well-known for its ability to produce two families of surfactant lipopeptides: Iturin A and Surfactin S1. Fermentation optimization for this strain was performed to amplify the ... [more ▼]

Bacillus subtilis S499 is well-known for its ability to produce two families of surfactant lipopeptides: Iturin A and Surfactin S1. Fermentation optimization for this strain was performed to amplify the surfactant production. Ten active variables were analyzed by two successive Plackett-Burman designs, consisting respectively of 12 and 16 experiments to give an optimized medium. The amount of biosurfactant lipopeptides in the supernatant of a culture carried out in this optimized medium was about five times higher than that obtained in nonoptimized rich medium. The analysis of the surfactant molecules produced in such optimized conditions has revealed the presence of a third family of lipopeptides: the fengycins. The time-dependent production of these three families of molecules in bioreactors showed that surfactin S1 is produced during the exponential phase and iturin A and fengycins during the stationary phase. [less ▲]

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See detailProtection Of Cucumber Against Pythium Root Rot By Fluorescent Pseudomonads: Predominant Role Of Induced Resistance Over Siderophores And Antibiosis
Ongena, MARC ULg; Daayf, F.; Jacques, Philippe ULg et al

in Plant Pathology (1999), 48(1),

Four Pseudomonas strains were evaluated for their intrinsic properties conferring their ability to protect long English cucumber against Pythium aphanidermatum in hydroponic culture. Two of the strains ... [more ▼]

Four Pseudomonas strains were evaluated for their intrinsic properties conferring their ability to protect long English cucumber against Pythium aphanidermatum in hydroponic culture. Two of the strains, BTP1 and its siderophorenegative mutant M3, increased plant yield as compared with the non-inoculated control plants. Strain BTP7 was intermediate in its biocontrol activity while strain ATCC 17400 failed to reduce disease development. The role of pyoverdines could not be confirmed since treatment with either BTP1 or its siderophore-negative mutant M3 provided similar suppression of Pythium disease. In addition, no siderophores were detected in the nutrient solution. BTP1 did not inhibit pathogen growth in vitro on several media, suggesting that antibiosis was not a mechanism of suppression. Quantification of root bacterial populations did not indicate differences among the strains. On the other hand, roots treated with either BTP1 or its sid¹ mutant M3 contained more antifungal phenolics than roots from any other treatments including controls. These results suggest that antifungal compounds induced by inoculation of cucumber roots with the fluorescent Pseudomonas strains BTP1 and M3 participate actively in the protection of cucumber plants against P. aphanidermatum [less ▲]

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See detailCharacterization of acetification enzymes from thermotolerant acetic acid bacteria, Acetobacter pasteurianus VM 136.
Mouanda, P.; Thonart, Philippe ULg; Tanazefti, H. et al

in Mededelingen Faculteit Landbouwkundige en Toegepaste Biologische Wetenschappen Universiteit Gent (1999), 64(5a),

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See detailMicroencapsulation Of Erythromycin And Clarithromycin Using A Spray-Drying Technique
Zgoulli, S.; Grek, V.; Barre, G. et al

in Journal of Microencapsulation (1999), 16(5), 565-71

Previous methods of microencapsulation are unable to process particles smaller than 100 microm without organic solvents or the use of multistep processes. The present study investigates the feasiblity of ... [more ▼]

Previous methods of microencapsulation are unable to process particles smaller than 100 microm without organic solvents or the use of multistep processes. The present study investigates the feasiblity of a one-step spray-drying process to microencapsulate erythromycin and clarithromycin, antibiotics known to have an unpleasant, bitter taste. Mixtures of clarithromycin (5% by weight) or erythromycin (30% by weight) with a biodegradable polymer were prepared and spray-dried under specific conditions of temperature and turbine speed. This process resulted in the microencapsulation of 80% of each drug as determined by high pressure liquid chromatography. Particle size ranged from 1 to 80 microm as determined by electron microscopy. These data show that microencapsulation of macrolides using a spray-drying technique is feasible. Spray-drying microencapsulation might be useful in the formulation of palatable oral suspensions of bitter tasting drugs. [less ▲]

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See detailModification of the Thermoresistance to Spray-Drying of a Cold-Adapted Subtilisin by Genetic Engineering
Bare, G.; Diakiese, A.; Zgoulli, S. et al

in Applied Biochemistry and Biotechnology (1999), 77-79(Spring), 857-65

The thermoresistance of a cold-adapted subtilisin dried by spray-drying was studied. Proteolytic activity of this enzyme was measured before and after spray-drying. Without chemical additives, spray ... [more ▼]

The thermoresistance of a cold-adapted subtilisin dried by spray-drying was studied. Proteolytic activity of this enzyme was measured before and after spray-drying. Without chemical additives, spray-drying yields ranged from 2-13%. The use of arabic gum and lactose in the composition of the enzyme solutions allowed the strengthening of the enzyme structures and increased water mobility in the product. Increase of water mobility led to a shorter residence time of the product in the spray-drier and a net yield increase was obtained (yield higher than 50%). The effect of two selective mutations on the thermoresistance to spray-drying of the cold-adapted subtilisin was also investigated. Mutation T85D (introduction of an additional link with an ion Ca2+ necessary for enzyme activity, by substitution of Asp for Thr 85) had no effect on the thermoresistance of the subtilisin to spray-drying. Mutation H121W (introduction of an additional aromatic link by substitution of Trp for His 121) reduced the drying yield from 66% (not modified subtilisin) to 52%. This higher thermosensitivity could be explained by an increase of the hygroscopic character of the modified subtilisin (mutation H121W). [less ▲]

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See detailA biological pluridisciplinary model to predict municipal landfill life
Steyer, E.; Hiligsmann, Serge ULg; Radu, Jean-Pol ULg et al

in Christensen; Cossu; Stegmann (Eds.) Proceedings Sardinia 99, Seventh International Waste Management and Landfill Symposium (1999)

The degradation processes occurring within landfills are the keys to assessment and control of their environmental impact. This degradation results from different microbial activities interacting all ... [more ▼]

The degradation processes occurring within landfills are the keys to assessment and control of their environmental impact. This degradation results from different microbial activities interacting all along the landfill lifetime and influenced by several non-biological factors. Approaching these complex biological and chemical processes requires a multidisciplinary pattern. Thanks to Walloon Region support, we have developed a pattern or model combining the evolution of different key parameters. Such parameters qualify biogas (composition, production rate), leachate (pH, BOD5, COD, volatile fatty acids, redox potential, nitrogen balance, humic acids...), or solid waste (moisture, settlement, cellulose content...). This paper presents relationships, including our model, between these parameters. Variations of pH, BOD5/COD ratio, sulphate concentration in leachates and settlement measures allows to predict landfill age since completion. Evaluation of cellulose and water content in refuse as well as settlement degree are useful to estimate the time required for complete biological degradation. The mathematical model has also been applied, with success, to the case of Anton Sclayn site. [less ▲]

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See detailLandfill management in Africa
Lardinois, M.; Kapepula, D.; Hiligsmann, Serge ULg et al

in Christensen; Cossu; Stegmann (Eds.) Proceedings Sardinia 99, Seventh International Waste Management and Landfill Symposium (1999)

Landfill management is an important matter to study in order to set up techniques respectful of the environment. Before any suggestions of management solutions, behaviour of landfills has to be ... [more ▼]

Landfill management is an important matter to study in order to set up techniques respectful of the environment. Before any suggestions of management solutions, behaviour of landfills has to be characterised. This is necessary to predict future interactions between a landfill and the neighbourhood, and to estimate the landfill lifetime. Water is one of the most important parameter implied in the biological degradation of refuse, which is a substantial source of pollution. Therefore, this parameter is characterised in terms of quantitative and qualitative data. A relationship between climatic conditions, one of the main source of water, and possible evolution of landfills is propounded. [less ▲]

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See detailL’évaluation biologique des décharges en relation avec les propriétés de perméabilité
Steyer, E.; Ourth, A.; Hiligsmann, Serge ULg et al

Scientific conference (1998, September 25)

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