Enhanced selectivity nanocellulose-based membranes for tangential flow filtration protein separation

The development of fully water-based membrane manufacturing approaches represents an important direction toward more sustainable filtration technologies in bioprocessing. The aim of this work was to demonstrate a facile membrane impregnation method for tailoring pore size distribution and achieving enhanced selectivity of protein separation using nanocellulose-based membranes. A series of graded nanocellulose-based membranes was prepared by poly(vinyl alcohol) (PVA) impregnation at varying concentrations (0, 0.5, 1, and 3% wt solution) to produce membranes with tunable size-exclusion characteristics. The membrane structural characteristics were assessed using thermoporometry by differential scanning calorimetry, hydraulic permeability, and Zeman-Wales particle rejection model. The retention of protein samples of varying molecular weight, i.e., 14 kDa (lysozyme), 66 kDa (human serum albumin), and 660 kDa (porcine thyroglobulin), was assessed by ultrafiltration in tangential flow filtration mode. The selectivity parameter, expressed as the ratio between sieving coefficients for a specific pair of proteins (i.e., α-factor), increased substantially with impregnation percentage, especially for larger protein pairs, in a controlled manner. It is concluded that precise separation between protein pairs over wide molecular weight ranges can be achieved using nanocellulose-based membranes by considering protein specific MW and selecting an appropriate PVA concentration.