TangenX manufactures ProStream™ and HyStream™ modified PES membranes validated for use in cGMP processes. Both membrane chemistries are available in our NovaSet™ and Sius™ ultrafiltration cassettes. We also die cut from sheet stock these membranes into standard disc formats, and custom configurations upon request.
ProStream™ (PP) – This PES membrane has been modified to minimize its protein adsorption characteristics due to non-specific binding. Due to these unique characteristics, the process flux is enhanced and product yield is higher than with unmodified PES membranes. ProStream membranes are ideally suited for many critical downstream TFF processing applications where product recovery is most important. ProStream™ modified PES membranes provide the highest possible performance and recovery under a wide range of conditions, while exhibiting excellent chemical compatibility. Available in 0.65kD, 1kD, 3kD, 5kD, 10kD, 30kD, 50kD, 100kD, 300kD.
HyStream™ (XP) – This PES membrane has been modified to be significantly more hydrophilic than standard PES membranes. It is resistant to fouling by hydrophobic species such as fats, lipids, anti-foams, and other similar highly fouling substances. HyStream™ modified PES membranes prevent the dramatic decrease in flow rate that typically occurs with many upstream and early downstream TFF processing applications where hydrophobic species are present. Optimal flow rates are achieved for fast, efficient processing. Available in 5kD, 10kD, 30kD, 50kD, 100kD, 300kD, 0.1um , 0.2um, 0.45um, and 0.65um.
HyStream – the performance of regenerated cellulose with the robustness of modified PES!
Pore Size Distribution and Selectivity
The selective portion of an ultrafiltration membrane is the shiny surface layer known as the “skin” of the membrane. The layer beneath the skin is made up of a “finger-pore” structure that supports the skin and facilitates liquid flow. Examination of the scanning electron micrograph above (above right) shows the porous substructure of the TangenX ProStream™ 10K membrane. The uniform finger pores of this substructure allow for minimal particle entrapment which results in low fouling and maximum fluid flow. TangenX has developed this membrane substructure to ensure a defect-free surface and provide maximum adhesion to the substrate while achieving highest possible flow rates.
UF membranes are rated for pore size in kilodaltons (kD) and are based on nominal molecular weight cutoff (MWCO). MWCO is the ability of a membrane to retain 90% of a globular macromolecule of defined molecular weight. Unlike microporous membranes, UF membranes do not have an absolute micron rating (e.g., retain 100% of a macromolecule of the rated pore size) because all pores are not the same size. Instead, UF membranes utilize nominal molecular weight cutoffs that are a measure of the pore size distribution across the membrane surface. The more uniform the pore size, the better the membrane’s selectivity is. A narrow pore size distribution enables UF membranes to have high selectivity; that is, the ability to differentiate between macromolecules of a more similar size. The membrane selectivity curves shown to the right graphically represent the selectivity profile of several different membrane molecular weight cutoffs offered by TangenX. Each membrane selectivity curve is distinctly separated from one another with no overlap and show a high degree of selectivity. These are very desirable attributes for ultrafiltration membranes which lead to higher process performance and product yield.
Membrane Selection Guidelines: Factors to Consider for Optimal Performance
TangenX recommends selecting a molecular weight cutoff (MWCO) that is 3 to 6 times smaller than the protein or other molecule you want to retain. If obtaining highest possible flow rates is most critical to your application, then choose a more open MWCO membrane at the lower end of the range (3x). If retention is your main concern, then choose a tighter MWCO membrane at the upper end of the range (6x). Please keep in mind that certain factors can influence the selectivity and retentivity of a membrane. The shape of a molecule, presence of other solutes, pressure, adsorption and ionic conditions may affect membrane performance.
Membrane Cut Discs
Membrane discs are often times useful for screening diferent membrane pore sizes and chemistries. Our cut discs are available in common diameters to fit conventional stirred cells and our X-Flo76 membrane screening system. Discs are disposable; however, if appropriate cleaning measures are taken, they may be washed and reused typically 10 to 20 times. If you have unique requirements, call with your special die configuration needs.
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X-Flo76 Tangential Flow Test Cell
TangenX has developed a TFF cell that utilizes 76mm membrane discs. A unique “spiral” flow path in the X-Flo76 allows fluid to be directed across the surface of the membrane, creating cross-flow shear conditions that are more representative of true scale-up. Unlike traditional stirred cells, the X-Flo76 uses a pump as the filtration driving force for better TMP control and optimal scale-up performance. Play the video below to learn more about the XFlo-76 device and see it in operation!