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Membrane Separation (membrane + separation)
Terms modified by Membrane Separation Selected AbstractsHandbook of Membrane Separations By Anil K. Pabby, Syed S.H. Rizvi, and Ana Maria SastreAICHE JOURNAL, Issue 11 2009Glenn Lipscomb No abstract is available for this article. [source] A novel purification strategy for retrovirus gene therapy vectors using heparin affinity chromatographyBIOTECHNOLOGY & BIOENGINEERING, Issue 4 2005María de las Mercedes Segura Abstract Membrane separation and chromatographic technologies are regarded as an attractive alternative to conventional academic small-scale ultracentrifugation procedures used for retrovirus purification. However, despite the increasing demands for purified retroviral vector preparations, new chromatography adsorbents with high specificity for the virus have not been reported. Heparin affinity chromatography is presented here as a novel convenient tool for retrovirus purification. The ability of bioactive retroviral particles to specifically bind to heparin ligands immobilized on a chromatographic gel is shown. A purification factor of 63 with a recovery of 61% of functional retroparticles was achieved using this single step. Tentacle heparin affinity supports captured retroviral particles more efficiently than conventional heparin affinity chromatography supports with which a lower recovery was obtained (18%). Intact, infective retroviral particles were recovered by elution with low salt concentrations (350 mM NaCl). Mild conditions for retrovirus elution from chromatographic columns are required to preserve virus infectivity. VSV-G pseudotyped retroviruses have shown to be very sensitive to high ionic strength, losing 50% of their activity and showing membrane damage after a short exposure to 1M NaCl. We also report a complete scaleable downstream processing scheme for the purification of MoMLV-derived vectors that involves sequential microfiltration and ultra/diafiltration steps for virus clarification and concentration respectively, followed by fractionation by heparin affinity chromatography and final polishing by size-exclusion chromatography. Overall, by using this strategy, a 38% yield of infective particles can be achieved with a final purification factor of 2,000. © 2005 Wiley Periodicals, Inc. [source] Technology options for new nutritional conceptsINTERNATIONAL JOURNAL OF DAIRY TECHNOLOGY, Issue 2 2002Hannu Korhonen Recent advances in the food and nutrition sciences support the concept that the diet has a significant role in the modulation of various functions in the body. The diet and/or its components may contribute to an improved state of well-being, a reduction of risks related to certain diseases and even an improvement in the quality of life. These new concepts have led to the introduction of a new category of health-promoting foodstuffs, i.e. functional foods. The concern about health embraces a number of driving issues, needs and opportunities which may be approached by designing specific diets from various food raw materials. These tailor-made products provide physiological benefits that are targeted at particular consumer groups. The functionality of functional foods is based on bioactive components, which may be contained naturally in the product but usually require formulation by appropriate technologies in order to optimise the desired beneficial properties. To this end, it is often necessary to develop and apply novel technologies, e.g. membrane separation, high hydrostatic pressure and supercritical fluid extraction techniques. Also the minimal processing concept could be employed in this context. This review discusses the current technological options available and the future challenges faced in the area. Particular attention is paid to the exploitation of bovine colostrum and milk-derived bioactive compounds for the development of functional foods. [source] CLARIFICATION OF WATERMELON (CITRULLUS LANATUS) JUICE BY MICROFILTRATIONJOURNAL OF FOOD PROCESS ENGINEERING, Issue 6 2008Ch. CHHAYA ABSTRACT Microfiltration of watermelon juice was conducted using stirred membrane cell in continuous mode. The experiments were conducted at operating pressures of 136.5, 204.7 and 276 kPa, and stirring speeds 1,200 rpm (Re = 1.40 × 105), 1,400 rpm (Re = 1.63 × 105) and 1,600 rpm (Re = 1.87 × 105). Permeate flux decline was analyzed using a first-order kinetic model, and correlations were developed for the steady-state polarized layer resistance with the operating conditions, e.g., transmembrane pressure difference, Reynolds number and membrane resistance. The permeate flux was calculated based on the developed correlation, and found to be in good agreement with the actual experimental flux. The change in quality parameters of clarified juice was marginal compared to that of original juice. PRACTICAL APPLICATIONS The application of membrane technology is one of the emerging areas in food industry. The major application includes fruit juice clarification and concentration. Because of the nonthermal nature of membrane separation, the juice can be clarified at room temperature and packed aseptically for a longer shelf life without the loss of its initial quality parameters. The major problem during clarification is decline in permeate flux of fruit juice with time. Identification of causes for flux decline is essential for designing of membrane modules to make the clarification process commercially viable. The quality of juice during storage is vital, and therefore, determination of variation of its physicochemical properties during storage is also important. [source] Simulation of autothermal reforming in a staged-separation membrane reactor for pure hydrogen productionTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2008Anwu Li Abstract Steam methane reforming with oxygen input is simulated in staged-separation membrane reactors. The configuration retains the advantage of regular membrane reactors for achieving super-equilibrium conversion, but reaction and membrane separation are carried out in two separate units. Equilibrium is assumed in the models given the excess of catalyst. The optimal pure hydrogen yield is obtained with 55% of the total membrane area allocated to the first of two modules. The performance of the process with pure oxygen input is only marginally better than with air. Oxygen must be added in split mode to reach autothermal operation for both reformer modules, and the oxygen input to each module depends on the process conditions. The effects of temperature, steam-to-carbon ratio and pressure of the reformer and the area of the membrane modules are investigated for various conditions. Compared with a traditional reformer with an ex situ membrane purifier downstream, the staged reactor is capable of much better pure hydrogen yield for the same autothermal reforming operating conditions. Le reformage du méthane à la vapeur avec apport d'oxygène est simulé dans des réacteurs à membranes de séparation étagés. Cette configuration conserve l'avantage des réacteurs à membranes réguliers pour la conversion en sur-équilibre, mais la réaction et la séparation par membranes sont réalisées dans deux unités séparées. L'équilibre est supposé dans les modèles selon l'excès en catalyseur. Le rendement optimal en hydrogène pur est obtenu avec 55% de la surface totale des membranes affectée au premier des deux modules. La performance du procédé avec apport d'oxygène pur n'est que marginalement meilleure par rapport à l'air. De l'oxygène peut être ajouté en mode fractionné pour atteindre un fonctionnement autothermique pour les deux modules reformeurs, et l'apport d'oxygène de chaque module dépend des conditions de procédé. Les effets de la température, du rapport vapeur-carbone et de la pression du reformeur et de la surface des modules membranaires sont étudiés pour diverses conditions. Comparativement au reformeur traditionnel avec, en aval, un purificateur à membranes ex-situ, le réacteur étagé peut donner un bien meilleur rendement en hydrogène pur pour les mêmes conditions opératoires de reformage autothermique. [source] Scaleable purification process for gene therapy retroviral vectorsTHE JOURNAL OF GENE MEDICINE, Issue 4 2007Teresa Rodrigues Abstract Background Retroviral vectors (RVs) constitute one of the preferred gene therapy tools against inherited and acquired diseases. Development of scaleable downstream processes allowing purification under mild conditions and yielding viral preparations with high titer, potency and purity is critical for the success of clinical trials and subsequent clinical use of this technology. Methods A purification process for murine leukaemia virus (MLV)-derived vector supernatants was developed based on membrane separation and anion-exchange chromatography (AEXc). Initial clarification of the vector stocks was performed using 0.45 µm membranes followed by concentration with 500 kDa molecular weight cut-off (MWCO) membranes; further purification was performed by AEXc using a tentacle matrix bearing DEAE functional ligands. Finally, concentration/diafiltration was performed by 500 kDa MWCO membranes. To validate final product quality the process was scaled up 16-fold. Results Optimization of microfiltration membrane pore size and ultrafiltration transmembrane pressure allowed the recovery of nearly 100% infectious particles. Further purification of the RVs by AEXc resulted in high removal of protein contaminants while maintaining high recoveries of infectious vectors (77 ± 11%). Up-scaling of the process resulted in high titer vector preparations, 3.2 × 108 infectious particles (IP)/ml (85-fold concentration), with an overall recovery reaching 26%. The process yielded vectors with transduction efficiencies higher than the starting material and more than 99% pure, relative to protein contamination. Conclusions The combination of membrane separation and AEXc processes results in a feasible and scaleable purification strategy for MLV-derived vectors, allowing the removal of inhibitory contaminants thus yielding pure vectors with increased transduction efficiencies. Copyright © 2007 John Wiley & Sons, Ltd. [source] Prediction of gas sorption kinetics for porous media using MRIAICHE JOURNAL, Issue 9 2006Matthew J. Watt-Smith Abstract Diffusion and reaction within porous media involving condensable vapors are important processes in catalysis, fuel cells, and membrane separations. In this work, 3-D maps of the spatial variation of porosity, pore size and network tortuosity within a porous solid, derived from magnetic resonance images, have been used to construct a structural model for a mesoporous catalyst pellet. Simulations of the kinetic uptake, adsorption and capillary condensation of butane vapor within the porous solid, conducted on the structural model, have successfully predicted experimental measurements of the effects of the onset of capillary condensation on mass transfer rates without the need of the various adjustable parameters prevalent in other models. These findings suggest that accurate mathematical models for both the complex void space of the porous medium, and the mass transport processes taking place within it, have been successfully developed. © 2006 American Institute of Chemical Engineers AIChE J, 2006 [source] Hybrids of poly(ethylene oxide- b -amide-6) and ZrO2 sol,gel: Preparation, characterization, and application in processes of membranes separationADVANCES IN POLYMER TECHNOLOGY, Issue 1 2002Rita Aparecida Zoppi Abstract Hybrids consisting of poly(ethylene oxide- b -amide-6), PEBAXTM, and zirconium oxide were prepared from hydrolysis and condensation of zirconium tetraisopropoxide in solution containing the dissolved organic polymer. These hybrids were characterized by thermogravimetric analysis, differential scanning calorimetry, infrared spectroscopy, and electron microscopy. Results show that the incorporation of the inorganic phase seems to promote the degradation of the organic polymer. Composite membranes consisting of a porous support of poly(vinylidene fluoride), PVDF, and a filter layer of PEBAX/ZrO2 were prepared and characterized by electron microscopy. Permeation tests of water or aqueous solutions containing poly(ethylene glycol) of different molar masses were carried out to determine the permeation rate and the membrane cutoff respectively. To determine the phosphate retention, permeation tests using a KH2PO4 aqueous solution were carried out. Independent of composition of the filter layer, values of phosphate retention were nearly equivalent to 80%. © 2002 John Wiley & Sons, Inc. Adv Polym Techn 21: 2,16, 2002; DOI 10.1002/adv.10011 [source] | |||||||||||||||||||||||||