Neil Soice

Clarification of recombinant proteins from high cell density mammalian cell culture systems using new improved depth filters

Increasingly high cell density, high product titer cell cultures containing mammalian cells are being used for the production of recombinant proteins. These high productivity cultures are placing a larger burden on traditional downstream clarification and purification operations due to higher product and impurity levels. Controlled flocculation and precipitation of mammalian cell culture suspensions by acidification or using polymeric flocculants have been employed to enhance clarification throughput and downstream filtration operations. While flocculation is quite effective in agglomerating cell debris and process related impurities such as (host cell) proteins and DNA, the resulting suspension is generally not easily separable solely using conventional depth filtration techniques. As a result, centrifugation is often used for clarification of cells and cell debris before filtration, which can limit process configurations and flexibility due to the investment and fixed nature of a centrifuge. To address this challenge, novel depth filter designs were designed which results in improved primary and secondary direct depth filtration of flocculated high cell density mammalian cell cultures systems feeds, thereby providing single‐use clarification solution. A framework is presented here for optimizing the particle size distribution of the mammalian cell culture systems with the pore size distribution of the gradient depth filter using various pre‐treatment conditions resulting in increased depth filter media utilization and improved clarification capacity. Feed conditions were optimized either by acidification or by polymer flocculation which resulted in the increased average feed particle‐size and improvements in throughput with improved depth filters for several mammalian systems. Biotechnol. Bioeng. 2013; 110: 1964–1972.

A novel primary amine-based anion exchange membrane adsorber☆

A novel anion exchange membrane adsorber is presented which shows excellent impurity removal under different buffer conductivities ranging from 2 to 2 7mS/cm. The membrane utilizes a primary amine ligand (polyallylamine) and was designed specifically to bind impurities at high salt concentrations. Studies with DNA, endotoxin, and virus spiked into buffer at varying salt conditions were done, resulting in clearance of >3, 4, and 4 LRV, respectively, with negligible change on increasing salt up to 27 mS/cm conductivities. Verification of virus removal in mAb feedstocks is also shown. The data are compared with other membrane adsorbers and a conventional resin which utilize traditional chemistries to demonstrate improved purification performance with the primary amine ligand. Additional data on scale-up of the membrane adsorber device is discussed. A stacked flat-sheet design was implemented to ensure linear scale-up of performance using bovine serum albumin (BSA) as a model. The linearly scalable device, coupled with the highly effective membrane for virus, DNA, and endotoxin removal, represents a step forward in polishing technology for the purification of monoclonal antibodies and recombinant proteins.