Development of a Microfiltration Process for the Purification of Precipitated Monoclonal Antibodies and Crystallized Proteins

Monoclonal antibodies are one of the most important drug classes because of their ability to target specific pathogens or cell receptors. However, they are also one of the most expensive classes of drug on the market, in part because of the high cost of the downstream purification process. In this work, we examined the use of continuous tangential flow microfiltration for the purification of precipitated / crystallized proteins. Experiments were performed with suspensions of two model proteins: immunoglobulin G (IgG), which was selectively precipitated using ZnCl₂ and polyethylene glycol, and human serum albumin (HSA), which was crystallized using CeCl₃. Microfiltration was performed through polyethersulfone hollow-fiber membrane modules, with the critical flux evaluated using a flux-stepping procedure to determine the maximum flux before the onset of fouling. The size and morphology of the precipitated IgG particles, evaluated by optical microscopy, were found to be a function of the precipitation conditions, such as the addition of specific salts, buffers, and pH. These changes in morphology had a significant impact on the fouling behavior of the membrane and could thus be leveraged to optimize the precipitate dewatering and washing performance. This work also provided the first demonstration that it was possible to dewater crystallized protein by tangential flow microfiltration, with the yield of protein crystallization and the membrane performance being a function of the concentrations of CeCl₃ and polyethylene glycol used for the crystallization. These results demonstrate the potential of developing a low-cost platform for purification of high-value therapeutics proteins using precipitation / crystallization in combination with tangential flow microfiltration.