Simulation d'une interface entre un mélange trioléine-acide oléique et l'eau: analyse de la tension interfaciale et de l'organisation des lipides.

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Lipids behaviour in aqueous solution of disrupted microalgae cultivated under nitrogen starving conditions: molecular simulation compared to experimental study of representative synthetic mixtures

International audienceThis work deals with the microalgae culture and biorefinery for biofuel production. Microalgae transform CO 2 into biomass and valuable molecules, including lipids. The downstream processing to valorise intracellular compounds necessitates innovative, efficient and clean processes for biomass harvesting, concentration, cell disruption and fractionation. Membrane filtration is a promising process for the concentration and the purification of lipids in a wet pathway to produce biofuel. The behaviour of the biomolecules and particles during the filtration processes is unknown. Yet it drives their performances. For example, strong interactions between lipids and polar molecules released during the cell disruption may prevent an efficient separation and valorisation of both compounds because of the water-oil interface stabilisation. Consequently, to achieve oil droplets coalescence, the interface must be disturbed during filtration. The understanding of the local organisation on the target molecules is a necessary step to develop innovative fractionation strategies and optimize the coupling of different processes. To bring understanding, a multiscale approach is proposed. The use of synthetic mixtures drives the link between the different scales. These synthetic mixtures are simplified emulsions that mimic a supernatant of a real grinded biomass, centrifugated to get rid of cell fragments. The composition is based on the characterisation of disrupted cells samples, from a P. kessleri culture, under nitrogen starving conditions. The synthetic mixtures contain water, triglycerides and polar lipids. On the one hand, coarse-grained molecular simulations were carried out, to study the behaviour of lipids in the solution. Interfacial tension of the water-lipids interface was calculated for several compositions and validated with experiments. On the other hand, the interfacial properties of complex mixtures were related to molecular organisation deduced from molecular simulation. The perspective of this project is at first the characterization of water-lipid interfaces with real products, to compare to the results with synthetic solutions. This necessitates a large-scale culture in starving conditions to recover enough lipids in the supernatant. The acquired knowledge on the behaviour and organisation of lipids at the interfaces will help the optimization of membrane processes for the concentration and coalescence of lipids before valorisation into biofuels

Recovery of lipids from microalgae extracts by membrane processes: Comparison of cross-flow and shear-enhanced filtration performances

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Shear-enhanced membrane filtration of model and real microalgae extracts for lipids recovery in biorefinery context

International audienceIn this work, the hydrodynamic effects of rotating disk filtration (with maximum shear rates of 16 000 s −1 and 66 000 s −1) were evaluated and compared with the crossflow filtration (16 000 s −1) in the recovery of lipids from a model solution that simulates the characteristics of Parachlorella kessleri aqueous extracts. Four polymeric membranes were tested. The PAN 500 kDa membrane along with the rotating disk filtration presented the best performances for lipid concentration and coalescence. The rotating disk filtration was tested with real microalgae extracts, confirming the total lipid retention and the limited membrane fouling

Membrane fitration for the recovery of lipids from microalgae extracts

International audienc

Characterisation of the fouling of an ultrafiltration polyethersulfone membrane fouled by an emulsion modelling lipids issued from Microalgae

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Concentration des lipides issus de Parachlorella kessleri en voie humide : effet de la destruction cellulaire sur la performance du procédé de fractionnement par membrane

International audienceLe bioraffinage de microalgues a pour but de produire des biomolécules (lipides, protéines, polysaccharides, pigments, etc.) pour divers secteurs industriels tels que l'alimentation, la cosmétique, la pharmacie, l'énergie ou la chimie verte. Le défi dans ce domaine consiste à développer une cascade de procédés doux et efficaces afin de garantir l'intégrité des molécules fragiles ainsi qu'une production économe en énergie et respectueuse de l'environnement. Pour la production à grande échelle, un bioraffinage en voie humide a été proposé afin de limiter les coûts de séchage, la dégradation de molécules thermolabiles et l'utilisation de solvant. Les différentes étapes proposées sont : la récolte de la biomasse, le broyage des cellules pour libérer les composés intracellulaires d'intérêts dans la phase aqueuse, puis leur fractionnement par procédé membranaire et leur purification. Le verrou au développement de ce procédé est le manque de maîtrise de l'impact des procédés de déconstruction cellulaire sur les procédés de fractionnement. Les travaux présentés ici ont pour but d'étudier l'impact du broyage à billes sur les performances du procédé de filtration membranaire, pour séparer les lipides (triglycérides, phospholipides et glycolipides) des composés hydrosolubles (protéines et sucres) produits lors d'une culture carencée de Parachlorella kessleri. La quantité de molécules cibles libérées (lipides, protéines, sucres) dans la phase aqueuse, l'état de ces molécules (possible dégradation des composés cibles en raison de l'activité enzymatique ou de l'oxydation) et leur organisation dans le mélange complexe dépendent fortement des conditions de broyage et de clarification de la suspension. Ces paramètres déterminent également la qualité de la séparation. Des filtrations membranaires de surnageants issus de suspensions obtenues dans diverses conditions de broyage de Parachlorella kessleri sont réalisées à l'aide d'une membrane préalablement sélectionnée. Les performances (flux, taux de rétention) sont comparées. Les conditions opératoires optimales sont enfin choisies, permettant le couplage entre le procédé de destruction cellulaire et le procédé de fractionnement par membrane, et la séparation des lipides et des composés hydrosolubles

Cross-flow filtration for the recovery of lipids from microalgae aqueous extracts: membrane selection and performances

International audienceThe biorefinery of microalgae necessitates innovative choices of soft and energy-efficient processes to guarantee the integrity of fragile molecules and develop eco-friendly production. A wet processing of biomass is proposed, which avoids expensive drying steps. It includes harvesting, cell disruption, and fractionation of the target compounds. Membrane filtration is a promising clean fractionation step. In this paper, the recovery of lipids from starving Parachlorella kessleri aqueous extracts by cross-flow filtration was studied. A model solution was formulated to test four membranes of different materials (PVDF, PES, PAN) and cut-offs (200 kDa - 1.5 µm). The hydrophilic PAN 500kDa membrane presented the best performance (flux stability, permeate flux, lipid retention, and cleanability) and was therfore selected for filtrating real aqueous extracts. Similar permeation fluxes were obtained with model and real products: 34 -41Lh-1m-2 respectively. The coalescence of lipid droplets was observed with model solutions but not with real products, less concentrated. The lipids from the real products were wholly retained by the PAN membrane, whereas some of the polysaccharides and proteins were able to permeate. An optimization of the coupling between culture, cell disruption, clarification, and filtration would allow a good concentration and purification of the lipids from microalgae

Fractionnement de biomolécules issues des microalgues: exemple du couplage entre broyage et filtration membranaire

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