The test results demonstrated excellent scale-up performance of the Stax assembly with a volumetric throughput at a differential pressure of 1.0 bar within 2% for the Stax 20 m2 compared to the 2 m2 system. The results also demonstrated that the Stax filter scaled to within 3% of the other sheet filter formats.
Prior to full product launch of the Pall Stax product range, trials with prototype filter assemblies were conducted with several leading biotech companies to assess performance and gain valuable feedback on the design. One such application was the clarification of a bacterial toxin for use in production of a vaccine product.
Due to the hazardous nature of the product, the process developers wanted to assess the feasibility of transferring the existing process to a single-use depth-filtration system.
The current process is validated with Seitz depth-filter modules for the clarification of the toxin from the bacteria. A two-stage depth-filtration system is used with a coarser prefilter grade followed by a finer-grade prior to a sterile-filtration step. Trials were performed using the same grade of filter media contained within the Pall Stax capsule format and operated within a Stax lab-scale chassis.
The trials took place with a scaled-down product batch volume, while operating under the same parameters as those used for the production process, i.e., filter sheet rating, feed volume per unit area of filter, and feed flow rate (l/m2/hr) were maintained constant.
The trials were run until the feed volume had been processed or when a differential pressure of 1.0 bar was reached. The results are shown in Figure 3.