Macroporous PES Composite Membranes Built on an sPES-Containing Asymmetric Platform for Improved Fermentation-Broth Filtration

High clean-water throughput does not necessarily translate into rapid fermentation-broth filtration. We hypothesized that a macroporous upstream layer combined with an asymmetric polyethersulfone (PES) membrane could unite rapid filtration at low broth concentration with improved performance under a greater fouling challenge. Development progressed from symmetric and asymmetric manufacturing platforms through layered proof-of-concept tests to a PES composite. Preliminary asymmetric-PES/nitrocellulose assemblies increased average broth flux 4.81-fold at 100-fold dilution and 3.74-fold at 50-fold dilution relative to their respective bare-base controls. A separately cast PES upstream layer was then developed using mixed polyethylene-glycol additives and vapor/non-solvent-induced phase separation. The selected 40 µm layer had an open particulate morphology and a clean-water flux of 147,000 L m^-2 h^-1. Its composite filtered 100 mL of 50-fold diluted Escherichia coli broth in 52.35 s versus 185 s for an asymmetric-base reference. Subsequent upstream incorporation of 0.5 wt% acid-form sulfonated PES improved composite broth flux 1.77-2.25-fold despite lower isolated-layer water flux; both tested coupons exceeded two commercial references in the same session. The final PES and PES/sPES-H composites were compared at 50-fold dilution only. These results support the architectural hypothesis and establish a third-generation PES composite through coordinated development of upstream morphology, composition and interlayer contact.