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See detailAphid-ant mutualism: how honeydew sugars influence the behaviour of ant scouts
Detrain, Claire; Verheggen, François ULg; Diez, Lise et al

in Physiological Entomology (2010), 35(2), 168-174

Honeydew is the keystone on which ant-aphid mutualism is built. The present study investigates how each sugar identified in Aphis fabae Scopoli honeydew acts upon the feeding and the laying of a ... [more ▼]

Honeydew is the keystone on which ant-aphid mutualism is built. The present study investigates how each sugar identified in Aphis fabae Scopoli honeydew acts upon the feeding and the laying of a recruitment trail by scouts of the aphid-tending ant Lasius niger Linnaeus, and thus may enhance collective exploitation by the ant mutualists. The feeding preferences shown by L. niger for honeydew sugars are: melezitose = sucrose = raffinose > glucose = fructose > maltose = trehalose = melibiose = xylose. Although feeding is a prerequisite to the launching of trail recruitment, the reverse is not necessarily true: not all ingested sugar solutions elicit a trail-laying behaviour among fed scouts. Trail mark laying is only triggered by raffinose, sucrose or melezitose, with the latter sugar being specific to honeydew. By comparing gustatory and recruitment responses of ant foragers to sugar food sources, the present study clarifies the role of honeydew composition both as a source of energy and as a mediator in ant-aphid interactions. Lasius niger feeding preferences can be related to the physiological suitability of each sugar (i.e. their detection by gustatory receptors as well as their ability to be digested and converted into energy). Regarding recruitment, the aphid-synthesized oligosaccharide (melezitose) could be used by ant scouts as a cue indicative of a long-lasting productive resource that is worthy of collective exploitation and defence against competitors or aphid predators. [less ▲]

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See detailCorrigendum to "Quantitative and qualitative study of spelt and wheat fibres in varying milling fractions
Escarnot, Emmanuelle; Agneessens, Richard; Wathelet, Bernard ULg et al

in Food Chemistry (2010), 122

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See detailInfluence de la teneur en galactose sur les interactions moléculaires et sur les propriétés physico-chimiques des galactomannanes en solution
Dakia, Patrick Aubin; Wathelet, Bernard ULg; Paquot, Michel ULg

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

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See detailComparison of the glucooligosaccharide profiles produced from maltose by two different transglucosidases from Aspergillus niger
Goffin, Dorothée ULg; Wathelet, Bernard ULg; Blecker, Christophe ULg et al

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

Prebiotic isomaltooligosaccharide preparations contain α-D-glucooligosaccharides and their structure is the key factor for their prebiotic potential. The transglucosylation selectivity is known to depend ... [more ▼]

Prebiotic isomaltooligosaccharide preparations contain α-D-glucooligosaccharides and their structure is the key factor for their prebiotic potential. The transglucosylation selectivity is known to depend on the enzyme specificity and moreover, maltose and -glucooligosaccharides can actually act as both glucosyl donor and acceptor in the reaction. Thus, two commercial enzymes, a glycosyl-tranferase and an -glucosidase, were tested alone and in combination on pure maltose to study their specificities and the IMO profile obtained. The reactions were monitored using a step-forward AEC-PAD analytical method which permitted to detect and resolve new unknown IMO. Structural determination of unknown IMO was attempt using their retention times and relative abundance. As a general rule, the -glucosidase has a more expressed hydrolyzing activity leading to products containing less residual digestible -(1-4) linkages such as isomaltose, isomaltotriose, isomaltotetraose, kojibiose and nigerose while the glucosyl-transferase produces important amount of panose. Finally, the combination of the two enzymes leaded to an intermediate IMO profile. IMO syrups composition was thus proved to be dependant on the specificity of the transglucosylating enzyme so that products profiles can be designed using different enzymes and in different proportion. [less ▲]

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See detailMicrowave-assisted synthesis of D-glucuronic acid derivatives using cost-effective solid acid catalysts
Richel, Aurore ULg; Laurent, Pascal ULg; Wathelet, Bernard ULg et al

in Tetrahedron Letters (2010), 51

Monomode microwave-assisted coupling of D-glucuronic acid with alcohols, in the presence of various impregnated acid catalysts, was successfully performed, affording in almost quantitative yields the ... [more ▼]

Monomode microwave-assisted coupling of D-glucuronic acid with alcohols, in the presence of various impregnated acid catalysts, was successfully performed, affording in almost quantitative yields the corresponding monosubstituted b-D-glucofuranosidurono-6,3-lactones in less than 10 min at 85°C. This study evidences the synergy of microwaves and impregnated acid catalysts as a fast and clean strategy in the field of carbohydrate chemistry. [less ▲]

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See detailPartial or total replacement of fish meal by local agricultural by-products in diets of juvenile African catfish (Clarias gariepinus): growth performance, feed efficiency and digestibility
Nyina-Wamwiza, Laetitia; Wathelet, Bernard ULg; Richir, Jonathan ULg et al

in Aquaculture Nutrition (2010), 16

The study was undertaken to evaluate the growth performance and feed utilization of African catfish, Clarias gariepinus, fed six diets (D) in which fishmeal (FM) was gradually replaced by a mixture of ... [more ▼]

The study was undertaken to evaluate the growth performance and feed utilization of African catfish, Clarias gariepinus, fed six diets (D) in which fishmeal (FM) was gradually replaced by a mixture of local plant by-products. In diets 1 and 2, FM (250 g kg)1) was replaced by sunflower oil cake (SFOC). In diets 3 and 4, FM (250 and 150 g kg)1, respectively) was replaced by SFOC and bean meal (BM) while FM was totally substituted by a mixture of groundnut oil cake (GOC), BM and SFOC in diets 5 and 6. Sunflower oil cake was cooked, soaked or dehulled in order to determine the appropriate processing techniques for improving the SFOC nutritive value and to evaluate the apparent digestibility coefficient (ADC) values of the alternative diets. No significant differences were observed for daily feed intake, weight gain, specific growth rate (SGR) and feed efficiency (FE) among fish fed D1, D2, D3 (250 g kg)1 FM), D4 (150 g kg)1 FM) and D6 (0 g kg)1 FM). The highest SGR (3.2% per day) and FE (1.2) were achieved in fish fed D3, and the lowest in fish fed D5 (0% FM), suggesting a maximum acceptable dietary concentration of hulled SFOC below 250 g kg)1 in African catfish juveniles. Protein efficiency ratio ranged from 2.2 to 3.2 for all dietary treatments and was positively influenced by FM inclusion. African catfish were able to digest plant protein very efficiently in all diets tested. ADC of protein ranged from 88.6 to 89.5%, while ADC of energy was relatively low for diets containing hulled sunflower oilcake (71–74%) and high when sunflower oilcake was dehulled (78.6–81.3%). Similarly, ADC of dry matter was higher when sunflower was dehulled (72.1%) when compared with crude SFOC (60.5%). Soaking increased ADC values for neutral detergent fibre (NDF), dry matter, energy, protein and amino acids (AA). There were no significant differences in protein ADCs (88–90%) with increased levels of dietary vegetable ingredients. Both soaking and dehulling of sunflower before incorporation helped in the reduction of NDF, antitrypsin and tannins. Digestibility of all AA was generally high, greater than 90% for both indispensable and non-indispensable AA. Based on the data obtained, it was possible to totally replace menhaden fish meal with a mixture of vegetable proteins (7 % of total dietary protein) when diets contained a relatively low percentage of animal protein (28% based on blood meal and chicken viscera meal) without negative effects. [less ▲]

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See detailAphid-ant mutualism: How do aphids focus ant foraging?
Verheggen, François ULg; Detrain, Claire; Diez, Lise et al

Conference (2009, August)

The mutualistic relationships that occur between myrmecophilous aphids and ants are based on the rich food supply that honeydew represents for ants and on the protection they provide against aphid natural ... [more ▼]

The mutualistic relationships that occur between myrmecophilous aphids and ants are based on the rich food supply that honeydew represents for ants and on the protection they provide against aphid natural enemies. While aphid predators and parasitoids actively forage for oviposition sites by using aphid semiochemicals, scouts of aphid-tending ant species would also benefit from locating honeydew resources by orienting toward aphid pheromone sources. The present study aims to identify the chemical factors that attract ants and that maintain their mutualistic relationships with aphids. The perception and behavioral impact of Aphis fabae alarm pheromone, namely (E)-β-farnesene, on Lasius niger were firstly investigated using electroantennography and a four-arm olfactometer. Aphis fabae honeydew sugar composition was subsequently analyzed while the foraging and recruiting behaviour of L. niger scouts towards each of the identified sugars was studied. Clear electrical depolarisations were observed from L. niger scout antennae to stimulations of A. fabae alarm pheromone. Scouts were significantly attracted toward (E)-β-farnesene in the four-arm olfactometer, suggesting for the first time that the latter compound is a key chemical in the establishment of the mutualism. Aphis fabae honeydew consisted of 9 identified mono-, di- and tri-saccharides and 8 hydrocarbons that could not be identified. The main identified sugars were sucrose, fructose, glucose and melezitose. L. niger scouts showed the following drinking preferences for the tested sugars: melezitose = sucrose = raffinose > glucose = fructose > maltose = trehalose = melibiose = xylose, with a recruitment launched toward the first three sugars. Therefore, ant scouts may use aphid semiochemicals to locate at distance an aphid colony and subsequently estimate honeydew quality by tasting it before recruiting conspecifics and establishing a mutualistic relationship. [less ▲]

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See detailNonribosomal peptides producing strains isolated from Bikalga and Soumbala fermented condiments of Burkina Faso
Savadogo, Aly; Chollet, Marlène; Tapi, Arthur et al

Conference (2009)

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See detailEgg and whole-body amino acid profile of African bonytongue (Heterotis niloticus) with an estimation of their dietary indispensable amino acids requirements
Momentcham, Serge-Eric; Wathelet, Bernard ULg; Pouomogne, Victor et al

in Fish Physiology and Biochemistry (2009)

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See detailA Step-Forward Method Of Quantitative Analysis Of Enzymatically Produced Isomaltooligosaccharide Preparations By Aec-Pad
Goffin, Dorothée ULg; Robert, Christelle; Wathelet, Bernard ULg et al

in Chromatographia (2009), 69(3-4),

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See detailCalorimetric study of milk fat/rapeseed oil blends and their interesterification products
Aguedo, Mario ULg; Giet, Jean-Michel ULg; Hanon, Emilien ULg et al

in European Journal of Lipid Science and Technology [=EJLST] (2009), 111(4), 376-385

Milk fat (MF) and rapeseed oil (RO) blends were analyzed by differential scanning calorimetry (DSC). It was shown that peak and onset temperatures can be used to determine the percentage of each fat in ... [more ▼]

Milk fat (MF) and rapeseed oil (RO) blends were analyzed by differential scanning calorimetry (DSC). It was shown that peak and onset temperatures can be used to determine the percentage of each fat in the blend and that the relative enthalpy of one peak assigned to low-melting triacylglycerols (TAG) can also be used to determine the percentage of RO in the blend. A linear relation was also established between IMF content of the blend and its dropping point (DP), indicating that DP can be linearly related with the above DSC data. A blend of MF/RO 70 : 30 (wt/wt) was then chosen as a model system for enzymatic interesterification (EIE). The applicability of DSC analyses to EIE products was checked and a correct correlation could be established between DSC values and the interesterification degree and DP. Among the data from the DSC profiles, the peak associated with low-melting TAG was the best indicator of the reaction course. In the same way, a high-melting MF stearin fraction was interesterified. with RO. In that case, onset temperatures and peak "a" were better reaction indicators than for the interesterified MF/RO blend. We therefore suggest that values from DSC endotherms could be used to monitor EIE of fat blends. [less ▲]

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See detailSynthèse et propriétés tensioactives de nouveaux surfactants provenant de matières premières renouvelables.
Laurent, Pascal ULg; Razafindralambo, Hary ULg; Wathelet, Bernard ULg et al

Poster (2009)

A l'heure actuelle, le bioraffinage se présente de plus en plus comme une alternative prometteuse aux filières pétrochimiques puisqu'il vise à la fois le remplacement d'une partie du pétrole comme source ... [more ▼]

A l'heure actuelle, le bioraffinage se présente de plus en plus comme une alternative prometteuse aux filières pétrochimiques puisqu'il vise à la fois le remplacement d'une partie du pétrole comme source d'énergie et le développement de produits chimiques issus de la biomasse (végétale principalement) tels que détergents, produits phytopharmaceutiques, dissolvants, matières plastiques, etc. La valorisation de carbohydrates provenant de matières premières renouvelables fait ainsi actuellement l'objet de nombreuses recherches. Dans ce cadre, la synthèse de nouveaux tensioactifs non ioniques dérivés des acides Dglucuronique et D-galacturonique a été effectuée. [less ▲]

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See detailEffect of protective compounds on the survival, electrolyte leakage and lipid degradation of freeze-dried Weissella paramesenteroides LC11 during storage.
Yao, Amenan Anastasie ULg; Wathelet, Bernard ULg; Thonart, Philippe ULg

in Journal of Microbiology and Biotechnology (2009), 19(8), 810-817

The effect of cryoprotectants (maltodextrin+glycerol) and cryoprotectants+antioxidant [ascorbic acid and/or butylated hydroxytoluene (BHT)] mixtures on the survival, electrolyte leakage, and lipid ... [more ▼]

The effect of cryoprotectants (maltodextrin+glycerol) and cryoprotectants+antioxidant [ascorbic acid and/or butylated hydroxytoluene (BHT)] mixtures on the survival, electrolyte leakage, and lipid degradation of freeze-dried Weissella paramesenteroides LC11 during storage was investigated and compared with that of the control (cells without additives) over a 90-day storage period at 4 or 20 degrees in glass tubes with water activity (a(w)) of 0.23. The survival, electrolyte leakage, and lipid degradation were evaluated through colony counts, electrical conductivity, and thiobarbituric acid reactive substances (TBARS) content, respectively. The fatty acids composition was determined by gas chromatography, in both the total lipid extract and the polar lipid fraction, and compared with that of the control after the 90-day storage period. As the storage proceeded, increases in leakage value and TBARS content, as well as a decrease in viability, were observed. After 90 days of storage, the major fatty acids found in both the total lipid extract and the polar lipid fraction were palmitic (16:0), palmitoleic (16:1), stearic (18:0), oleic (18:1), linoleic (18:2), and linolenic (18:3) acids. The survival, leakage value, TBARS content and 18:2/16:0 or 18:3/16:0 ratio were the greatest for the protected strain held at 4 degrees . Cells with the cryoprotectants+BHT mixture showed the highest percentage of survival and 18:2/16:0 or 18:3/16:0 ratio in both lipid extracts, as well as the lowest leakage value and TBARS content after the 90-day storage period. Drying cells with the cryoprotectants+BHT mixture considerably slowed down polar lipid degradation and loss of membrane integrity, resulting in improved viability during storage. [less ▲]

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See detailPolar lipids analysis from the MFGM by SPE and HPLC-ELSD
Bodson, Pascal ULg; Danthine, Sabine ULg; Blecker, Christophe ULg et al

Poster (2008, January 23)

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See detailAnalyse des lipides polaires de la MFGM par SPE et HPLC-ELSD
Bodson, Pascal ULg; Danthine, Sabine ULg; Blecker, Christophe ULg et al

in CRAW Gembloux (Ed.) Treizième Carrefour des Productions Animales : Vérités et Contre-Vérités (2008, January 23)

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See detailCombining Feed, Food and Non-Food Uses of Lupin for Sustainability
Froidmont, E.; Delcarte, J.; Wathelet, Jean-Paul ULg et al

in III International Scientific Symposium "Farm Machinery and Process Management in Sustainable Agriculture (2008)

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See detailCharacterization of pectins extracted from banana peels (Musa AAA) under different conditions using an experimental design
Happi Emaga, Thomas ULg; Ronkart, Sébastien ULg; Robert, Christelle et al

in Food Chemistry (2008), 108(2), 463-471

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