References of "Richard, Gaetan"
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See detailInteractions of natural rhamnolpids produced by Pseudomonas aeruginosa with plant model membranes
Polo Lozano, Damien ULg; Nasir, Mehmet Nail ULg; Deleu, Magali ULg et al

Poster (2015, January 30)

It is well known that chemical pesticides have harmful effects on human health and environment. In this context, the interest for alternative products such as biopesticides is increasing. Among them ... [more ▼]

It is well known that chemical pesticides have harmful effects on human health and environment. In this context, the interest for alternative products such as biopesticides is increasing. Among them, elicitors act on the plants by inducing systemic resistance against diseases caused by fungal, viral, bacterial agents and insects. Rhamnolipids are surface active molecules produced mainly by various strains of the bacterium Pseudomonas aeruginosa. These secondary metabolites are composed of one to three fatty acids with various chain lengths linked through a glycosidic bond to one or two rhamnose moieties. The fatty acids are linked together through an ester bond. These molecules have shown several biological activities including plant defense stimulation. It has been suggested that this elicitor activity could be related to an interaction of rhamnolipids with the lipid bilayer of the plant plasma membrane (PPM) and lead to its destabilization, which can activate the plant defense signaling pathways. In this context, interactions of two rhamnolipids (Rha-C10-C10 and Rha-Rha-C10-C10) with biomimetic membranes of PPM such as Langmuir monolayers and multilayers were investigated using biophysical and in silico approaches. [less ▲]

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See detailBiochemical characterisation of the seed oils of four safflower (Carthamus tinctorius) varieties grown in north-eastern of Morocco
Ben Moumen, Abdessamad; Mansouri, Farid; Richard, Gaetan ULg et al

in International Journal of Food Science & Technology (2015)

The quality of the oil of four safflower varieties, originating from Spain (Rancho), India (Sharda) and Morocco (Cartamar and Cartafri), which were cultivated at the experimental station in Oujda (a semi ... [more ▼]

The quality of the oil of four safflower varieties, originating from Spain (Rancho), India (Sharda) and Morocco (Cartamar and Cartafri), which were cultivated at the experimental station in Oujda (a semi-arid region of eastern Morocco) was evaluated through analysis of their phenolic and carotenoid contents. The composition of the phenolic compounds of safflower oil has not yet been documented. Therefore, in this preliminary study, Thirty different phenolic compounds were identified, and significant differences between the oil varieties were observed (P < 0.05). In the seed oil from the Rancho and Sharda safflower varieties, the main phenolic compound was trans-chalcone, representing 13.45% and 11.8%, respectively, of the total phenolics, whereas in Cartamar and Cartafri oils, naringin accounted for 26.82% and 16.5%, respectively, of the total phenolics. The total carotenoid contents ranged from 1.13 mg/kg (Rancho) to 1.34 mg/kg (Cartamar and Cartafri).We observed that b-cryptoxanthin (0.31–0.37 mg/kg) and b-carotene (0.3–0.35 mg/kg) were the predominant carotenoids in all of the safflower oils that were studied. [less ▲]

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See detailEvaluation of the oxidative stability of blends of ‘Arbequina’ olive oils with other monovarietal olive oils
Mansouri, F.; Ben Moumen, A.; Houmy, N. et al

in Olivae (Official Journal of the International Olive Council) (2014), 120

Like elsewhere in the Mediterranean, the olive oil sector is one of the strategic branches of the Moroccan economy owing to its social and economic significance. This research entailed evaluation of the ... [more ▼]

Like elsewhere in the Mediterranean, the olive oil sector is one of the strategic branches of the Moroccan economy owing to its social and economic significance. This research entailed evaluation of the oxidative stability of olive oils made up of a blend of ‘Arbequina’ olive oil with ‘Arbosana’ and ‘Koroneiki’ monovarietal oils known for their high content of natural antioxidants (phenols and tocopherols) and their superior oxidative stability compared with ‘Arbequina’ oil. The monovarietal oils produced from the ‘Arbequina’, ‘Arbosana’ and ‘Koroneiki’ varieties, which have recently been introduced under intensive cultivation in the eastern region of Morocco, underwent physico–chemical characterisation to determine quality criteria, natural antioxidant content, fatty acid composition and triacylglycerol profile. The Rancimat test* was performed to assess the oxidative stability of these monovarietal oils and their three-variety blends. The oxidation tests were performed on five freshly prepared blends (A) of the three varieties – ‘Arbequina’/’Arbosana’/‘Koroneiki’ – according to the following volume ratios: A1: 60/30/10; A2: 60/20/20; A3: 60:10:30; A4: 50:25:25 and A5: 40:30:30. The test results show that blends A4 and A5 displayed the best oxidative stability, recording respective values of 72.67 h and 75.42 h. These results are comparable to those obtained for ‘Arbosana’ monovarietal oil (75.42 h), which is considered to be relatively stable. Hence, blending is an excellent tool for enhancing oils produced from varieties which, despite their excellent initial quality and their organoleptic attributes, are handicapped by their poor stability, as is the case of ‘Arbequina’ oil. [less ▲]

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See detailUse of lipases for the kinetic resolution of lactic acid esters in heptane or in a solvent free system
Richard, Gaetan ULg; Nott, Katherine; Nicks, François et al

Poster (2014, February 07)

This poster illustrates the kinetic resolution of lactic acid esters using CAL-B as catalyst. The racemic mixture is resolved in heptane and even in a solvent free system.

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See detailEffect of sun-drying on flavonoïd composition and antioxidant activity of three dark fig varieties
Bachir Bey, M.; Richard, Gaetan ULg; Fauconnier, Marie-Laure ULg et al

Poster (2014, February 07)

The aim of the study was to investigate the effect of sun-drying on individual flavonoïd and antioxidant activities of three dark fig varieties (Azenjar, Bouankik, and Aberkane). Flavonoïd compounds were ... [more ▼]

The aim of the study was to investigate the effect of sun-drying on individual flavonoïd and antioxidant activities of three dark fig varieties (Azenjar, Bouankik, and Aberkane). Flavonoïd compounds were identified and quantified using high-performance liquid chromatography. The results showed that all samples significantly differed in their flavonoïd compositions. [less ▲]

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See detailTechnologie de production de masse d’insectes - INSECTECH
Richard, Gaetan ULg; Hance, Thierry; Fauconnier, Marie-Laure ULg et al

Report (2014)

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See detailTechnologie de production de masse d’insectes - INSECTECH
Richard, Gaetan ULg; Hance, Thierry; Fauconnier, Marie-Laure ULg et al

Report (2013)

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See detailUse of response surface methodology for the optimization of the lipase-catalyzed synthesis of mannosyl myristate in pure ionic liquid
Galonde, Nadine ULg; Brostaux, Yves ULg; Richard, Gaetan ULg et al

in Process Biochemistry (2013), 48(11), 1914-1920

The purpose of the present study is to find the conditions allowing to reach the highest 24 h-yield(24 h- ) for the synthesis of mannosyl myristate catalyzed by the immobilized lipase B from Candida ... [more ▼]

The purpose of the present study is to find the conditions allowing to reach the highest 24 h-yield(24 h- ) for the synthesis of mannosyl myristate catalyzed by the immobilized lipase B from Candida antarctica (Novozym®435) in the ionic liquid (IL) [Bmpyrr][TFO] (1-butyl-1-methylpyrrolidinium tri-fluoromethanesulfonate). A full factorial design (FFD) was used in order to study the influence of three variables (temperature, mannose/vinyl myristate ratio and total substrate quantity) on the 24 h- . This design led to a model based on a second order polynomial response function. The resulting predicted con-tour plots have shown that the highest 24 h- should be obtained with high temperatures, low sugar/vinylester molar ratio and intermediate total substrate quantities (mmol). The model has been successfully verified and experimentally confirmed at the optimal conditions of 80◦C, substrate molar ratio of 1/10and total substrate quantity of 0.26 mmol leading to the highest predicted 24 h- of 72.2%. [less ▲]

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See detailUse of lipases for the kinetic resolution of lactic acid esters in heptane or in a solvent free system
Richard, Gaetan ULg; Nott, Katherine ULg; Nicks, François et al

in Journal of Molecular Catalysis B : Enzymatic (2013), 97

tKinetic resolution of d,l-ethyl lactate (d,l-LA-Et) and d,l-butyl lactate (d,l-LA-Bu) was accomplished inthe presence of lipases. Transesterification of the lactate esters with alcohols was shown to be ... [more ▼]

tKinetic resolution of d,l-ethyl lactate (d,l-LA-Et) and d,l-butyl lactate (d,l-LA-Bu) was accomplished inthe presence of lipases. Transesterification of the lactate esters with alcohols was shown to be poorlyenantioselective, with a very low preference toward the l enantiomer. However, esterification of the freehydroxyl function of the lactate esters was much more enantioselective, with an opposite preferencetoward the d form. Among the 200 combinations screened (substrates and lipases), only two reactionsfulfilled the required criteria for an efficient resolution (fast reaction, enantioselectivity ratio higherthan 100). The best resolution was obtained by esterification of d,l-LA-Bu with butyric anhydride inthe presence of lipase B from Candida antarctica (CAL-B) in heptane (at 30◦C): LA-Bu was resolved in6 h with an initial esterification rate of d-LA-BU of 1.5 g L−1h−1g−1EZ, an enantioselectivity ratio higherthan 100, a l substrate consumption lower than 1%, and a final substrate enantiomeric excess superiorto 99%. After having demonstrated that neither LA-Bu nor BuAn were inhibitors of CAL-B, the reactionwas further improved by carrying it out in a solvent free system, at an elevated temperature (60◦C), andat a higher lipase concentration. LA-Bu was resolved in 6 h with an initial rate of 7.6 g L−1h−1g−1EZ, anenantioselectivity ratio higher than 100, and a final substrate enantiomeric excess of 95%. [less ▲]

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See detailAmphiphilic structure-surface property relationships of monosaccharide-based surfactants
Razafindralambo, Hary ULg; Nicks, Francois ULg; Richard, Gaetan ULg et al

Poster (2013, April 08)

A set of monosaccharide-based renewable surfactants has been prepared, structurally checked, and systematically screened for different activities and functionalities. These compounds vary in the polar ... [more ▼]

A set of monosaccharide-based renewable surfactants has been prepared, structurally checked, and systematically screened for different activities and functionalities. These compounds vary in the polar head group, linker, and hydrophobic tail. Beyond the goal to find out the most potential valuable surfactants for each measurement, relationships between chemical structure, basic properties, and functionalities have been examined by comparing compounds differing in a single structural variable. In this paper, we show and explain the impact of the anomeric alpha or bêta, neutral or acid sugar derivatives, equatorial or axial position of hydroxyl group, alkyl chain substitute attachment position, number, and length on surface properties of sugar-based surfactants. [less ▲]

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See detailStudy of the Influence of Pure Ionic Liquids on the Lipase-catalyzed (Trans)esterification of Mannose Based on their Anion and Cation Nature
Galonde, Nadine ULg; Nott, Katherine ULg; Richard, Gaetan ULg et al

in Current Organic Chemistry (2013), 17(7), 763-770

A screening of nine ionic liquids (ILs) has been carried out in order to study the influence of the anion's and cation's nature and structure on the synthesis of mannosyl myristate by (trans ... [more ▼]

A screening of nine ionic liquids (ILs) has been carried out in order to study the influence of the anion's and cation's nature and structure on the synthesis of mannosyl myristate by (trans)esterification catalyzed by Novozym® 435. The best ILs in terms of yield (η) and initial rate (v0) are those based on the TFO- anion. The 24h yield (24h-η) reached 64.9% in [Bmim][TFO] and 70.9% in [Bmpyrr][TFO] by transesterification while it reached 29.7% and 44.5% respectively in each IL by esterification. [Bmpyrr][TFO] based on the pyrrolidinium cation gave the best results although this cation has been rarely used for biocatalysis. This work has thus highlighted a cation that could be further studied in biocatalysis of glycosylated compounds. The study of the relationship between the structure of the ILs and the v0 and η for the biocatalysis of mannosyl myristate showed that the lipase effectiveness is influenced by the anions while the cations have an indirect influence on the interaction strength between Novozym® 435 and the anions. [less ▲]

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See detailReusability study of Novozym® 435 for the enzymatic synthesis of mannosyl myristate in pure ionic liquids
Galonde, Nadine ULg; Richard, Gaetan ULg; Deleu, Magali ULg et al

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2013)

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See detailEnzymatic synthesis, surface and lipid interaction properties of novel rhamnolipids
Nott, Katherine ULg; Richard, Gaetan ULg; Deleu, Magali ULg

Conference (2013)

Amongst glycolipidid biosurfactants, rhamnolipids have drawn particular attention as they have several interesting biological properties such as antimicrobial, antiphytoviral, zoosporicidal and plant ... [more ▼]

Amongst glycolipidid biosurfactants, rhamnolipids have drawn particular attention as they have several interesting biological properties such as antimicrobial, antiphytoviral, zoosporicidal and plant defense elicitor activities [1-3]. It is generally recognised that these activities must be linked to the interaction of these molecules with constituents of biological membranes [4] but the detailed mechanism is far from being fully understood. The objective of this work is double. First, it aims to investigate a new strategy of synthesis for the production of novel rhamnolipids [5] that could exhibit properties as promising for industrial and environmental applications as their natural counterparts while avoiding the use of the pathogenic Pseudomonas aeruginosa for their production. Secondly, their basic surface properties (critical aggregation concentration, surface tension at CAC and interfacial behaviour of their monolayer) and their interaction with model membranes are investigated in relation with their structure in order to give insight about the mechanism of their biological actions. [1] Vatsa P. et al. Int. J. Mol. Sci. 2010;11:5095. [2] Varnier A-L. et al. Plant, Cell Environ. 2009;32:178. [3] Lang S. et al. Appl. Microbiol. Biotechn. 1999;51:22. [4] Aranda F.J. et al. Langmuir. 2007;23:2700. [5] Nott K. et al. Process Biochemistry, http://dx.doi.org/10.1016/j.procbio.2012.11.019 [less ▲]

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See detailEnzymatic synthesis and surface properties of novel rhamnolipids
Nott, Katherine ULg; Richard, Gaetan ULg; Laurent, Pascal ULg et al

in Process Biochemistry (2013), 48

New rhamnolipids were obtained via the development of a synthesis procedure consisting of two biocatalyzed steps. In the first step, naringinase was used to introduce a primary alcohol function onto ... [more ▼]

New rhamnolipids were obtained via the development of a synthesis procedure consisting of two biocatalyzed steps. In the first step, naringinase was used to introduce a primary alcohol function onto rhamnose by glycosylation of 1,3-propanediol. In the second step, immobilized lipase B from Candida antarctica catalyzed the esterification of the primary hydroxyl group with mono- and di-carboxylic fatty acids of increasing chain length (from C8 to C14). For the monoic acids, the initial rate and 24 h yield decreased with increasing chain length. For the dioic acid, the number of carbon atoms of the acid did not influence these parameters. The new rhamnolipid obtained with tetradecanoic acid showed very good surface properties. At pH 5, it had a very low critical aggregation concentration of 1.70 M and it diminished water’s surface tension to 27.6 mN/m. It was also able to form stable insoluble monolayers. On the other hand, the rhamnolipid formed with tetradecanedioic acid showed far less interesting surface properties. [less ▲]

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See detailGreen synthesis and antioxidant activity of new PEGylated ferulic acids
Nicks, Francois ULg; Richel, Aurore ULg; Richard, Gaetan ULg et al

in Tetrahedron Letters (2012), 53(19), 2402-2405

PEGylation of ferulic acid is described through a green esterification process involving poly(ethylene glycol) (PEG) with three different average molecular weights (200, 400 and 1000 g/mol) as both ... [more ▼]

PEGylation of ferulic acid is described through a green esterification process involving poly(ethylene glycol) (PEG) with three different average molecular weights (200, 400 and 1000 g/mol) as both reactive and solvent. Esterification with PEG400 and PEG1000 leads to original compounds soluble in all proportions in water. These new compounds display an antioxidant activity similar to that of ferulic acid. [less ▲]

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See detailImpact of the alkyl chain carbon atom number of uronic acid-derivative surfactants on interfacial and colloidal systems
Razafindralambo, Hary ULg; Richard, Gaetan ULg; Laurent, Pascal ULg et al

Poster (2012, March 26)

Uronic acid-derivative surfactants represent today an attractive group of Carbohydrate-based amphiphilic compounds for both fundamental and practical reasons [1,2]. In the continuity of our screening of ... [more ▼]

Uronic acid-derivative surfactants represent today an attractive group of Carbohydrate-based amphiphilic compounds for both fundamental and practical reasons [1,2]. In the continuity of our screening of their basic properties, and the approach in establishing relationships between their structure and properties [3,4], the impact of the alkyl chain carbon atom number on interfacial and colloidal systems has been systematically investigated. In this communication, the effect of odd-even number of carbon atom from C11 to C18, and the particular behavior of long chain derivatives on interfacial properties, as well as their impact on the formation and stability of colloidal systems, are presented. Experimental approaches have been conducted by investigating their properties and behaviors at gas-liquid and liquid-liquid under dynamic, equilibrium, and oscillatory interfacial conditions. Results are completed by and discussed with single molecule models established by theoretical approaches. [1] Razafindralambo, H.;Blecker, C.; Paquot, M., Screening of Basic Properties of Amphiphilic Molecular Structures for Colloidal System Formation and Stability. In Amphiphiles: Molecular Assembly and Applications, American Chemical Society: 2011; Vol. 1070, pp 53-66. [2] Laurent, P.; Razafindralambo, H.; Wathelet, B.; Blecker, C.; Wathelet, J.; Paquot, M., Synthesis and Surface-Active Properties of Uronic Amide Derivatives, Surfactants from Renewable Organic Raw Materials. J. Surfactants Deterg. 2011, 14, 51-63. [3] Razafindralambo, H.; Richel, A.; Wathelet, B.; Blecker, C.; Wathelet, J.; Brasseur, R.; Lins, L.; Miñones, J.; Paquot, M., Monolayer properties of uronic acid bicatenary derivatives at the air-water interface: effect of hydroxyl group stereochemistry evidenced by experimental and computational approaches. Physical chemistry chemical physics: PCCP 2011, 13 15291-15298. [4] Razafindralambo, H.; Blecker, C.; Mezdour, S.; Deroanne, C.; Crowet, J.; Brasseur,R.; Lins, L.; Paquot, M., Impacts of the Carbonyl Group Location of Ester Bond on Interfacial Properties of Sugar-Based Surfactants: Experimental and Computational Evidences. The journal of physical chemistry. B 2009, 113, 8872-8877. [less ▲]

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See detailStructure, properties and obtention routes of flaxseed lignan secoisolariciresinol
Sainvitu, Pauline ULg; Nott, Katherine ULg; Richard, Gaetan ULg et al

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2012), 16(1), 115-124

Following a brief description of the structure and nomenclature of the lignan family, this review focuses on the flaxseed lignan secoisolariciresinol (SECO). The main properties, the analysis methods and ... [more ▼]

Following a brief description of the structure and nomenclature of the lignan family, this review focuses on the flaxseed lignan secoisolariciresinol (SECO). The main properties, the analysis methods and two routes for the preparation of SECO, i.e. extraction from renewable raw material and (hemi)-synthesis, are reviewed. Green methods recently developed for the first route and chemical syntheses inspired from biosyntheses for the second one are the main subjects of this paper. [less ▲]

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