Recent studies of protein fouling have provided initial flux decline during the stirred cell filtration of considerable insight into both the underlying fouling bovine serum albumin (BSA) was associated with the mechanisms and the mathematical description of the flux deposition of large protein aggregates on the membrane decline. However, most of the data have been obtained surface. Similar results were obtained by Chandavarkar with a single model protein, making it difficult to general-(1990) and Meireles et al. (1991) in cross-flow microfilize the results to commercially relevant process streams. Experiments were thus performed using a range of pro-tration experiments employing BSA. Scanning electron teins with different physicochemical characteristics to demicrographs clearly confirm the presence of BSA aggretermine the relationship between the protein structure
gates on the surface of fouled microfiltration memand fouling behavior. Fouling in these systems occurred branes (Belfort et al., 1994;Kelly and Zydney, 1994; by two distinct mechanisms: deposition of large protein Kim et al., 1993). Mathematical descriptions of protein aggregates and chemical attachment of native proteins to the growing deposit. The chemical attachment generally fouling have generally employed one of the standard occurred via the formation of intermolecular disulfide fouling models based on pore blockage, pore constriclinkages involving a free sulfhydryl group in the native tion, and/or cake formation (Belfort et al., 1994; Hlava-protein. Proteins without a free sulfhydryl group were cek and Bouchet, 1993).
typically unable to form these intermolecular linkages.
Several recent studies have provided evidence that
The quasi-steady flux for the different proteins was pro-BSA fouling in microfiltration is best described using a portional to the square of the protein surface charge density, consistent with a model in which protein deposition two-stage fouling model in which the initial fouling is occurs when the drag force on the proteins associated described using some type of pore blockage model with with the convective filtrate flow is sufficient to overcome the longer-term fouling due to external cake formation electrostatic repulsive interactions. These results clearly model (Jonsson et al., 1996;Tracey and Davis, 1994).
demonstrate the importance of the protein structure, Kelly and Zydney (1995) developed a mathematical for charge, and reactivity in determining the rate and extent of protein fouling during microfiltration.