Procédés de fractionnement de la matière végétale : application à la production des polysaccharides du son et de la paille de blé

Le son et la paille de blé, riches en hémicelluloses, sont deux co-produits de la récolte de blé, abondants et renouvelables, mais qui restent à mieux valoriser. Dans le but d'extraire ces hémicelluloses, possédant plusieurs propriétés intéressantes (filmogènes, épaississantes, émulsifiantes, stabilisantes…), un procédé de fractionnement a été élaboré. Ce procédé consiste, après extraction alcaline, en la purification des extraits hémicellulosiques obtenus. Deux techniques ont été appliquées : l'ultrafiltration et la chromatographie sur résine échangeuse d'anions. L'ultrafiltration a permis de concentrer les extraits d'hémicelluloses et de les purifier en éliminant dans le perméat la plupart des molécules contaminantes, essentiellement les sucres libres et les sels minéraux. Les principales limitations de cette étape étaient la viscosité des extraits et les phénomènes de polarisation de concentration et de colmatage des membranes. La percolation sur résine, quant à elle, a permis de décolorer les extraits et de produire des poudres d'hémicelluloses plus claires en fixant certaines molécules colorées telles que les molécules possédant des groupements phénoliques. La combinaison des deux techniques a permis de produire des hémicelluloses pures à 60%. L'extrapolation du procédé à l'échelle pilote par l'utilisation d'un extrudeur bi-vis a permis d'obtenir des poudres d'hémicelluloses pures à 40%. ABSTRACT : Wheat bran and wheat straw are two by-products abundant and renewable, rich in hemicelluloses, but still not well valued. In order to extract these hemicelluloses characterized by their several interesting properties (film-forming, thickening, emulsifying, stabilizing…), a fractionation process was developed. This process consisted, after alkaline extraction, to purify the hemicellulosic extracts obtained. Two techniques were used: ultrafiltration and chromatography on anion exchange resin. The ultrafiltration allowed to concentrate the extracts and to purify them by removing in the permeate, the contaminating molecules, mostly free sugars and minerals. The main limiting factors of this stage were the extracts viscosity and the fouling of the membranes. The percolation on the resin discoloured the extracts and allowed to produce hemicellulosic powders with lighter colours and that by capturing the coloured compounds such as molecules with phenolic groups. The combination of the two techniques allowed the production of purified hemicelluloses; the purity was about 60%. The extrapolation of the process at a pilot scale using a twin-screw extruder allowed to obtain hemicelluloses with a purity of 40%

Comparison of different twin-screw extraction conditions for the production of arabinoxylans

The aim of this article is to compare two different sets of optimal conditions for twin-screw extraction of xylans and define their influence on the purification steps, combining ultrafiltration and industrial chromatography. Two xylan extracts were obtained by twin-screw extrusion of straw and bran. Condition 1 used a high straw/bran ratio (equal to 6) and high sodium hydroxide content, and condition 2 used a lower straw/bran ratio (equal to 2) and low sodium hydroxide content. Arabinoxylan extraction yields are slightly higher for conditions with low straw content (5.1% versus 4.4%). Nevertheless, these recovery yields remain between 9% and 10%. Ultrafiltration is as efficient as evaporation for polysaccharide concentration, with lower energy consumption, but also demineralizes the solution. The combination of ultrafiltration and chromatography gives partial purification of the extract with a final arabinoxylan purity ranging from 16% to 26%. This is slightly higher than by direct precipitation, but limited because all the large molecules such as proteins and lignins were retained by ultrafiltration

Performance evaluation of a semi-industrial production process of arabinoxylans from wheat bran

A process for hemicellulose fractionation and purification from wheat straw and bran has been investigated. The aim was to define the efficiency of a pilot scale process combining twin-screw extrusion and refining steps such as ultrafiltration and chromatography, to replace alcoholic precipitation. Extraction by twin-screw extrusion gave a complex extract containing only 22.7% carbohydrates. Evaporation (EV) followed by ethanol precipitation (P) and freeze-drying (FD), gave a 25.7% arabinoxylan yield with 24.1% arabinoxylan content. The other purification process studied was based on a combination of ultrafiltration (UF), anion exchange chromatography (CHR) and freeze-drying (FD), without precipitation. It gave a 24.3% yield of arabinoxylans into the hemicellulosic powders and 13.9% arabinoxylan content. Despite the obvious interest of using ultrafiltration for demineralization and anion exchange chromatography for decoloration, the purity of the final powder is still too low, because of difficulties in achieving separation of proteins and hemicelluloses and concentration of the solution, in the same step

Fractionation processes of plant material : application to the production of wheat bran and straw polysaccharides

Le son et la paille de blé, riches en hémicelluloses, sont deux co-produits de la récolte de blé, abondants et renouvelables, mais qui restent à mieux valoriser. Dans le but d'extraire ces hémicelluloses, possédant plusieurs propriétés intéressantes (filmogènes, épaississantes, émulsifiantes, stabilisantes…), un procédé de fractionnement a été élaboré. Ce procédé consiste, après extraction alcaline, en la purification des extraits hémicellulosiques obtenus. Deux techniques ont été appliquées : l'ultrafiltration et la chromatographie sur résine échangeuse d'anions. L'ultrafiltration a permis de concentrer les extraits d'hémicelluloses et de les purifier en éliminant dans le perméat la plupart des molécules contaminantes, essentiellement les sucres libres et les sels minéraux. Les principales limitations de cette étape étaient la viscosité des extraits et les phénomènes de polarisation de concentration et de colmatage des membranes. La percolation sur résine, quant à elle, a permis de décolorer les extraits et de produire des poudres d'hémicelluloses plus claires en fixant certaines molécules colorées telles que les molécules possédant des groupements phénoliques. La combinaison des deux techniques a permis de produire des hémicelluloses pures à 60%. L'extrapolation du procédé à l'échelle pilote par l'utilisation d'un extrudeur bi-vis a permis d'obtenir des poudres d'hémicelluloses pures à 40%.Wheat bran and wheat straw are two by-products abundant and renewable, rich in hemicelluloses, but still not well valued. In order to extract these hemicelluloses characterized by their several interesting properties (film-forming, thickening, emulsifying, stabilizing…), a fractionation process was developed. This process consisted, after alkaline extraction, to purify the hemicellulosic extracts obtained. Two techniques were used: ultrafiltration and chromatography on anion exchange resin. The ultrafiltration allowed to concentrate the extracts and to purify them by removing in the permeate, the contaminating molecules, mostly free sugars and minerals. The main limiting factors of this stage were the extracts viscosity and the fouling of the membranes. The percolation on the resin discoloured the extracts and allowed to produce hemicellulosic powders with lighter colours and that by capturing the coloured compounds such as molecules with phenolic groups. The combination of the two techniques allowed the production of purified hemicelluloses; the purity was about 60%. The extrapolation of the process at a pilot scale using a twin-screw extruder allowed to obtain hemicelluloses with a purity of 40%

Procédés de fractionnement de la matière végétale (application à la production des polysaccharides du son et de la paille de blé)

Le son et la paille de blé, riches en hémicelluloses, sont deux co-produits de la récolte de blé, abondants et renouvelables, mais qui restent à mieux valoriser. Dans le but d'extraire ces hémicelluloses, possédant plusieurs propriétés intéressantes (filmogènes, épaississantes, émulsifiantes, stabilisantes ), un procédé de fractionnement a été élaboré. Ce procédé consiste, apre s extraction alcaline, en la purification des extraits hémicellulosiques obtenus. Deux techniques ont été appliquées : l'ultrafiltration et la chromatographie sur résine échangeuse d'anions. L'ultrafiltration a permis de concentrer les extraits d'hémicelluloses et de les purifier en éliminant dans le perméat la plupart des molécules contaminantes, essentiellement les sucres libres et les sels minéraux. Les principales limitations de cette étape étaient la viscosité des extraits et les phénomènes de polarisation de concentration et de colmatage des membranes. La percolation sur résine, quant à elle, a permis de décolorer les extraits et de produire des poudres d'hémicelluloses plus claires en fixant certaines molécules colorées telles que les molécules possédant des groupements phénoliques. La combinaison des deux techniques a permis de produire des hémicelluloses pures à 60%. L'extrapolation du procédé à l'échelle pilote par l'utilisation d'un extrudeur bi-vis a permis d'obtenir des poudres d'hémicelluloses pures à 40%.Wheat bran and wheat straw are two by-products abundant and renewable, rich in hemicelluloses, but still not well valued. In order to extract these hemicelluloses characterized by their several interesting properties (film-forming, thickening, emulsifying, stabilizing ), a fractionation process was developed. This process consisted, after alkaline extraction, to purify the hemicellulosic extracts obtained. Two techniques were used: ultrafiltration and chromatography on anion exchange resin. The ultrafiltration allowed to concentrate the extracts and to purify them by removing in the permeate, the contaminating molecules, mostly free sugars and minerals. The main limiting factors of this stage were the extracts viscosity and the fouling of the membranes. The percolation on the resin discoloured the extracts and allowed to produce hemicellulosic powders with lighter colours and that by capturing the coloured compounds such as molecules with phenolic groups. The combination of the two techniques allowed the production of purified hemicelluloses; the purity was about 60%. The extrapolation of the process at a pilot scale using a twin-screw extruder allowed to obtain hemicelluloses with a purity of 40%.TOULOUSE-INP (315552154) / SudocSudocFranceF

Validation of a Rapid Multiresidue Method for the Determination of Pesticide Residues in Vine Leaves. Comparison of the Results According to the Different Conservation Methods

International audienceThe QuEChERS method was applied to the determination of pesticide residues in vine (Vitis vinifera) leaves by LC-MSMS. The method was validated in-house for 33 pesticides representing 17 different chemical groups, that are most commonly used in grape production. Recoveries for the pesticides tested ranged from 75 to 104%, and repeatability and reproducibility relative standard deviations (RSDr% and RSDRw%) were less than 20%. The method was applied to the analysis of pesticide residues in 17 market brands of vine leaves processed according to three different preservation methods and sampled from the Lebanese market. Dried vine leaves were more contaminated with pesticide residues than those preserved in brine or stuffed vine leaves. The systemic fungicides were the most frequently detected among all the phytosanitary compounds usually applied to grape production. Brine-preserved and stuffed vine leaves contained lower concentrations of the residues but still contained a cocktail of different pesticides

Twin-screw extrusion for hemicellulose recovery: Influence on extract purity and purification performance

International audienceA twin-screw extruder was used for the extraction of wheat bran hemicelluloses by the co-extrusion of wheat straw and bran. As compared with a stirred reactor extraction, a twin-screw extruder resulted in a lower extraction rate (only about 24% of hemicelluloses in the wheat bran), but it has the advantages of a shorter residence time for the vegetable matter and a lower chemical and water consumption. Hemicellulose powder production is usually effected via an expensive alcoholic precipitation step after concentration. Ultrafiltration was investigated as a means to reduce the alcohol consumption. Trials were made with hollow fiber polyethersulfone membranes with a molecular weight cut-off of 30 kDa. Ultrafiltration mainly concentrated the extract and removed small molecules such as monosaccharides and minerals. The combination of the anion-exchange chromatography and ultrafiltration allowed for the removal of colored compounds. (C) 2010 Elsevier Ltd. All rights reserved

Eco-conception of a production and purification process of Arabinoxylans from wheat straw and bran

National audienc

The Effects of Formulation on Imidacloprid Dissipation in Grapes and Vine Leaves and on Required Pre-Harvest Intervals under Lebanese Climatic Conditions

In this study, imidacloprid, a systemic insecticide, currently having a specified European Commission MRL value for vine leaves (2 mg kg−1), was applied on a Lebanese vineyard under different commercial formulations: as a soluble liquid (SL) and water dispersible granules (WDG). In Lebanon, many commercial formulations of imidacloprid are subject to the same critical good agricultural practice (cGAP). It was, therefore, important to verify the variability in dissipation patterns according to matrix nature and formulation type. Random samplings of grapes and vine leaves were performed starting at 2 days until 18 days after treatment. Residue extractions were performed according to the QuEChERS method and the analytical determination using liquid chromatography coupled to tandem mass spectrometry (LC-MS-MS). The SL formulation yielded significantly higher initial deposit than the WDG formulation on grapes and vine leaves. The formulation type did not significantly affect the dissipation rates; the estimated half-lives in grapes and vine leaves were 0.5 days for all imidacloprid formulations. No pre-harvest intervals were necessary on grapes. PHIs of 3.7 days for the SL formulation and 2.8 days for the WDG formulation were estimated on vine leaves. The results showed that the type of formulation and the morphological and physiological characteristics of the matrix had an effect on the initial deposits, and thus residue levels, but not on the dissipation patterns

Comparison of the efficacy of two insecticides for the management of Dactylopius opuntiae on prickly pear cactus in Lebanon and monitoring of the insecticides residues dissipation rates in fruits and cladodes

International audienceEnvironmental conditions and availability of new cultivated areas of prickly pear cactus in Lebanon appeared lately to be favourable for the survival and development of D. opuntiae which has become highly noxious. To thwart use of random chemicals and broad spectrum pesticides by local farmers, efficacy of sulfoxaflor (Closer™ 240 SC, rate 0.179 kg a.i/ha) and diflubenzuron (Dimilin® 25 W, rate 0.329 kg a.i/ha) was compared. Individual insecticidal solutions of each applied alone or in mixing with mineral oil (spray oil 7E, rate 1.010 kg a.i/ha) on potted cladodes in laboratory conditions (T = 23 ± 4 °C, RH = 58–63%) showed a sharp decrease in the number of individuals within colonies 48 h after treatment especially among first- and second-instar larvae. Similarly, the same insecticidal solutions applied on separate plots in field condi-tions (T = 20–35 °C, RH = 55–75%) according to the Good Agricultural Practices showed efficacious control of the pest development. D. opuntiae mortality mean percentage reached 80% and 72%, respectively, for sulfoxaflor and diflubenzu-ron 96 h after treatment. The added mineral oil acted as a synergist and enhanced efficacy of both insecticides. Mortality mean percentages increased to 92% and 88%, respectively. Insecticides residues content over time in fruits and cladodes were afterwards monitored. Samples were harvested at 3 days interval and residues extracted by the QuEChERS method and quantified by LC–MS. Dissipation rates after 30 days of treatment attained 70.8% and 80.6% in fruits and 98.5% and 74.0% in cladodes, respectively, for sulfoxaflor and diflubenzuron. Half-life time varied accordingly and was higher for fruits treated with sulfoxaflor (14.20 days) than for those treated with diflubenzuron (11.18 days). On contrary, for clad-odes, half-life time of the former (4.18 days) was lower than that of the latter (15.47 days). The addition of mineral oil into the spray solution of the insecticides increased their persistency in the crop. Consequently, half-life times increased and dissipation rates decreased. Findings of this study should enlarge the spectrum of chemical means for D. opuntiae management and promote resilience of the crop. Analytical method applied for residues analysis should be useful for registration of the insecticides on the crop and MRLs setting