Filterability of exopolysaccharides solutions from the red microalga Porphyridium cruentum by tangential filtration on a polymeric membrane

International audienceThe red microalga Porphyridium cruentum is exploited industrially for its exopolysaccharides (EPS) and pigments production. EPS produced by P. cruentum are partially released and dissolved into the surrounding environment, they can be recovered from the culture medium after removing the cells. This paper presents a parametric study of the ultrafiltration of EPS solutions on organic membrane. The EPS solutions were produced in conditions representative of an industrial production. They were filtered at lab-scale on a flat, PES 50 kDa MWCO membrane in a complete recirculation mode of permeate and retentate. Permeate flux-transmembrane pressure (TMP) curves were established up to the limiting flux for the filtration of solutions with various values of concentration in EPS (0.10 to 1.06 kg GlcEq.m), fluid tangential velocity (0.3 to 1.2 m.s) and temperature (20 and 40 °C). The reversible and irreversible parts of fouling were evaluated for each experiment and the critical flux was determined for an intermediate EPS concentration (0.16 kg GlcEq.m). The results showed that EPS solutions had a strong fouling capacity. When filtering the lowest concentrated solution (0.10 kg GlcEq.m) with moderate fouling conditions, the overall fouling resistance was approximately half of the membrane and the share of irreversible/reversible fouling was 88 and 12%. However, the part of reversible fouling becomes predominant when approaching the limiting flux. Permeate fluxes which were obtained allow to estimate that a VRR of approximately 10 could be obtained when concentrating EPS solutions using PES membranes in flat or tubular modules but not in spiral-wound

Exopolymers recovery from culture supernatants of Porphyridium cruentum using membrane techniques : study of the solutions filterability on an organic membrane and fouling characterization

Certaines microalgues peuvent excréter hors de la cellule des polysaccharides ayant des propriétés intéressant différents secteurs industriels (santé, cosmétique, agroalimentaire, etc.). Les exopolysaccharides (EPS) solubilisés dans le milieu de culture pourraient être concentrés et purifiés par filtration sur membrane après élimination des cellules. Dans ce contexte, la thèse a porté sur l’étude de la filtrabilité des solutions d’EPS de Porphyridium cruentum sur une membrane plane d’ultrafiltration en polyéthersulfone d’un seuil de coupure égal à 50 kDa muni d’un espaceur côté alimentation. Les solutions d’EPS ont été filtrées à petite échelle avec recyclage du rétentat et du perméat dans le bac d’alimentation. Des courbes flux de perméation-pression transmembranaire (PTM) ont été établies jusqu’au flux limite pour différentes conditions de vitesse tangentielle (de 0,3 à 1,2 m.s-1), de teneur en EPS (de 0,10 à 1,06 kg GlcEq.m-3) et de température (20 et 40 °C). Le colmatage de la membrane a été évalué par le biais du calcul des résistances hydrauliques de colmatage, du flux critique, et de cartographies FTIR-ATR et AFM du colmatage irréversible. Les résultats ont montré le caractère fortement colmatant des solutions d’EPS avec une prépondérance de la part du colmatage irréversible pour des pressions de filtration modérées et réverible pour des pressions proches de la PTM limite. Ainsi, la concentration des EPS d’un facteur 10 nécessiterait des vitesses tangentielles de l’ordre de 1 m.s-1, ce qui serait envisageable dans un module plan de type “filtre presse”, mais pas dans un module spiralé.Some microalgae are able to excrete polysaccharides featuring properties which are of high interest and value to various fields (health, cosmetics, food, etc.). The exopolysaccharides (EPS) solubilized in the culture medium could be concentrated and purified by membrane filtration after removing the cells. Within this context, the thesis focused on the study of the filterability of Porphyridium cruentum EPS solutions on a flat polyethersulfone ultrafiltration membrane with a 50 kDa molecular weight cut-off. The EPS solutions were filtered at a lab-scale with a complete recirculation of both retentate and permeate to the feed tank. Permeate fluxtransmembrane pressure (TMP) curves were established up to the limiting flux for the filtration of solutions with various values of cross-flow velocity (0.3 to 1.2 m.s-1), EPS concentration (0.10 to 1.06 kg GlcEq.m-3) and temperature (20 and 40 °C). Membrane fouling was evaluated through the calculation of hydraulic fouling resistances, the critical flux and FTIRATR and AFM mapping of the irreversible fouling. The results showed the high fouling power of the EPS solutions as well as the preponderance of the irreversible fouling at moderate filtration pressures and the reversible one at pressures close to the limiting TMP. Thus, concentrating EPS by a factor of 10 would require cross-flow velocities of 1 m.s-1, which would be feasible in a flat module (plate and frame filter press) but not in a spiral-wound module

Analyse par FTIR-ATR du colmatage irréversible d'une membrane organique après la filtration d'une solution d'exopolysaccharides de Porphyridium cruentum

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Filterability of exopolysaccharides solutions from the red microalga Porphyridium cruentum by tangential filtration on a polymeric membrane

International audienceThe red microalga is exploited industrially for its exopolysaccharides (EPS) and pigments production. EPS produced by are partially released and dissolved into the surrounding environment, they can be recovered from the culture medium after removing the cells. This paper presents a parametric study of the ultrafiltration of EPS solutions on organic membrane. The EPS solutions were produced in conditions representative of an industrial production. They were filtered at lab-scale on a flat, PES 50 kDa MWCO membrane in a complete recirculation mode of permeate and retentate. Permeate flux-transmembrane pressure (TMP) curves were established up to the limiting flux for the filtration of solutions with various values of concentration in EPS (0.10-1.06 kg GlcEq m), fluid tangential velocity (0.3-1.2 m s) and temperature (20°C and 40°C). The reversible and irreversible parts of fouling were evaluated for each experiment and the critical flux was determined for an intermediate EPS concentration (0.16 kg GlcEq m). The results showed that EPS solutions had a strong fouling capacity. When filtering the lowest concentrated solution (0.10 kg GlcEq m) with moderate fouling conditions, the overall fouling resistance was approximately half of the membrane and the share of irreversible/reversible fouling was 88% and 12%. However, the part of reversible fouling becomes predominant when approaching the limiting flux. Permeate fluxes which were obtained allow to estimate that a VRR of approximately 10 could be obtained when concentrating EPS solutions using PES membranes in flat or tubular modules but not in spiral-wound

Concentration et purification d’exopolysaccharides de la micro-algue porphyridium cruentum par procédé membranaire

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Membrane processes for the microalage biorefinery : example of polysaccharides upgrading

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Comparison of thermochemolysis and classical chemical degradation and extraction methods for the analysis of carbohydrates, lignin and lipids in a peat bog

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