Single pass tangential flow filtration (SPTFF) is relatively straightforward to apply in bioprocessing, but it can be difficult to design and size the SPTFF module for a given application since the filtrate flux and degree of concentration that can be achieved in a single pass is highly dependent on the properties of the protein, buffer conditions, and feed flow rate, according to Andrew Zydney, PhD, director of the membrane science, engineering and technology (MAST) Center at Pennsylvania State University.

“The design of SPTFF processes has thus been largely empirical, requiring significant experimental investigation,” he says, pointing out that it’s still worth taking on these challenges of applying SPTFF in bioprocessing.

“It can provide inline concentration of process streams, enhancing the performance of subsequent unit operations—for example, by increasing the product concentration in the load to a chromatography column—and reducing the volume needed for any holding tanks,” Zydney explains. “Second, SPTFF can be used for final concentration with only a single pump pass, thereby enhancing product recovery—by reducing hold-up volume—while minimizing aggregation of labile products.”

So, Zydney and his colleagues developed a model for using SPTFF in bioprocessing. Zydney says that this work “provides a mathematical model for the filtrate flux, concentration factor, and pressure drop in SPTFF modules that specifically accounts for the properties of the protein feed stream—for example, the viscosity of the protein solution. [Consequently] this model can greatly facilitate the design of SPTFF processes, allowing biopharmaceutical manufacturers to more rapidly design and optimize SPTFF steps in their downstream process.”

That means that a bioprocessor can take advantage of the benefits of SPTFF without suffering from its shortcomings.