Optimization of bovine serum albumin concentration and diafiltration via tangential flow filtration

This study aims to optimize process parameters for the concentration and diafiltration of
a 100-L bovine serum albumin (BSA) solution, within 3-hour timeframe. The initial
solution contained 1 g/L BSA in phosphate buffered saline (PBS) with 250 mM NaCl,
and the final target was 5 g/L BSA in PBS with 137 mM NaCl. Given BSA’s molecular
weight of 66.5 kDa, Merk Millipore’s cassettes with Ultracel® 10 kDa membrane were
used. Process optimization was first conducted at a small scale using the Pellicon® XL
cassettes (50 cm² filtration area), and later validated at larger scale using the Pellicon® 3
cassettes (88 cm²) to confirm process scalability. Transmembrane pressure (TMP)
excursions were performed on 1 g/L and 5 g/L BSA solutions at three different feed flow
rates (3, 5, and 7 LPM/m²) to determine the optimal TMP and flow rate for protein
concentration. The optimal operating conditions were determined to be a TMP of 28 psi
and a feed flow rate of 7 LPM/m². Further evaluation revealed that the optimal BSA
concentration for diafiltration was 5 g/L. Using these optimal conditions, permeate
fluxes obtained from small-scale experiments were used to determine the required
volume and filter area for validation and scale-up. At the validated scale with Pellicon®
3, 1.2 L of BSA solution was successfully concentrated and buffer-exchanged within 2
hours and 58 minutes, achieving 81% BSA recovery. Thus, to process 100 L of BSA
solution within 3 hours, a minimum area of Ultracel® 10 kDa filter of 0.63 m² is
recommended.