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See detailSynthesis and Surface-Active Properties of Uronic Amide Derivatives, Surfactants from Renewable Organic Raw Materials
Laurent, Pascal ULg; Razafindralambo, Hary ULg; Wathelet, Bernard ULg et al

in Journal of Surfactants and Detergents (2011), 14(1), 51-63

Short chemical syntheses were developed to produce a new set of surfactants from uronic acids derived from widely available raw material. Three different strategies were used to synthesise uronic amide ... [more ▼]

Short chemical syntheses were developed to produce a new set of surfactants from uronic acids derived from widely available raw material. Three different strategies were used to synthesise uronic amide derivatives, the structures of which were totally characterized by spectrometric methods (IR, MS, 1H-RMN and 13C-RMN). The best one, using an acid chloride as synthetic intermediate, furnished the expected amides as a mixture of anomers in 46 to 58 % global yield. Surface-active properties (CMC, g cmc, Tmax, Amin) of homologous series of uronic acid N-alkylamides from C8 to C18 were also assessed. In general, these sugar-based surfactants exhibited good surface-activities, and appeared as valuable non ionic surfactants compared to Triton X-100, the most well-known non ionic surfactant. Increasing the alkyl chain length influenced the CMC values for both glucuronic and galacturonic N-alkylamide derivatives. The galacturonic N-alkylamides decreased g cmc at slower values than their counterpart's glucuronic N-alkylamides. [less ▲]

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See detailSynthèse assistée par Micro-ondes de dérivés d'acides uroniques
Laurent, Pascal ULg; Richel, Aurore ULg; Wathelet, Bernard ULg et al

Poster (2010, October 14)

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 detailCARBOHYDRATE-BASED SURFACTANTS FOR FORMING AND STABILIZING COLLOIDAL SYSTEMS AS EMULSIONS AND FOAMS
Razafindralambo, Hary ULg; Blecker, Christophe ULg; Richel, Aurore ULg et al

in Abstracts book of 5th edition of world congress on emulsions (2010, October 12)

Carbohydrate-based surfactants (CBS) constitute a class of amphiphilic molecules with particular and common interests. These surface-active compounds can be produced from the most abundant renewable ... [more ▼]

Carbohydrate-based surfactants (CBS) constitute a class of amphiphilic molecules with particular and common interests. These surface-active compounds can be produced from the most abundant renewable materials allowing large product concept possibilities, and may occur in a large structural range with one or more hydrophilic head groups and hydrophobic chains with various linkers/spacers, thanks to numerous reactive functional groups in their basic structure. It is then possible to design a quasi-unlimited number of new compounds by (bio)-synthesis from various raw materials. This structural diversity can generate a wide range of properties, which could be developed in food and non-food applications. Our challenge is now to find out the most suitable molecular structures for the post-development of CBS, mainly for colloidal systems like emulsion, foam, and suspension. A pre-screening of the dynamic and equilibrium interfacial tensions and interfacial rheology properties of various CBS prepared by chemical, enzymatic, or chemo-enzymatic synthesis routes from the derivatives of bio-renewable substrates is carried out. Then, the characterization of emulsifying and foaming properties of pre-selected molecules is performed. These investigations are completed by the characterization of thermal properties of liquid suspensions and powders. Homologous series of two derivative compounds of glucuronic and galacturonic acids with mono- or bicatenar hydrophobic chains and different linkages (linear or cyclic ester, amide) have been chosen as CBS starting compounds. These were full characterized by spectroscopic techniques (RMN, SM, IR). The effect of the hydrophobic chain length and number, polar head group, and the linker on whole properties investigated is easily deduced. [less ▲]

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See detailMicrowave-assisted conversion of carbohydrates. State of the art and outlook.
Richel, Aurore ULg; Laurent, Pascal ULg; Wathelet, Bernard ULg et al

Conference (2010, May)

The valorisation of carbohydrates arising from the hydrolysis of renewable feedstocks (i.e. lignocellulosic biomass) is nowadays an area of outmost interest. In this context, the implementation of fast ... [more ▼]

The valorisation of carbohydrates arising from the hydrolysis of renewable feedstocks (i.e. lignocellulosic biomass) is nowadays an area of outmost interest. In this context, the implementation of fast, expeditous and cost-effective methodologies for the modification of these naturally occurring compounds is becoming a prerequisite. In this sense, the application of microwaves has gained progressive attention in laboratories for making a range of high-added value sugars derivatives scaffolds. Its advantages are numerous and include enhacement of reaction rates and yields combined to improved regio-, chemo- and anomeric selectivities. Since the first publications of Gedye et Giguere in 1986, the use of microwave has progressively emerged as a popular non conventional heating source in the field of organic synthesis.1 Nevertheless, its application in the area of carbohydrate chemistry is less documented.2, 3 Although research in this field is still in its infancy, recourse to microwaves often provides, with remarkable yields and atom efficiency, new carbohydrate-based structures that are not easily available by any another means (or only via painstaking multi-step protocols). This communication proposes therefore selected, recent and non exhaustive illustrations of the application of microwaves to promote famous carbohydrates “model” reactions. The scale-up of such microwave-assisted reactions is also presented. [less ▲]

Detailed reference viewed: 106 (13 ULg)
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 detailCellular engineering of Bacillus subtilis to enhance the biosynthesis of highly active anti fungal lipopeptides
Guy, J.; Guez, Jean-Sébastien; Coucheny, F. et al

Poster (2010)

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See detailQuantitative and qualitative study of spelt and wheat fibers in varying milling fractions
Escarnot, Emmanuelle ULg; Agneessens, Richard; Wathelet, Bernard ULg et al

in Food Chemistry (2010), 122

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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 detailNRPS molecules producing strains isolated from Bikalga and Soumbala fermented condiments of Burkina Faso.
Savadogo, A.; Chollet-Imbert, M.; Tapi, A. et al

Conference (2009)

Detailed reference viewed: 22 (1 ULg)