ABSTRACT

Simultaneous micro- and ultra-filtration was used to recover a recombinant monoclonal antibody from mammalian cell culture. Performance of micro-filtration was affected by the choice of base used to control pH in cell culture. A higher viable cell density and titer could be maintained with sodium hydroxide, while stable viability and higher sialic ratio were obtained with sodium carbonate. Lysis, rejection coefficient and resistance (ratio of trans-membrane pressure to permeation rate) data were internally consistent. MF resistance was higher for the sodium hydroxide lots. Product retained by the MF membranes de-sialylated with increasing lysis during operation, while product in the MF permeate retained its level of glycosylation. The MF membranes also retained multimeric forms of the product, known to have lower sialylation. The MF permeate was concentrated on UF membranes and then filtered through a polishing filtration train before downstream processing. DNA and protein aggregates were found to increase in size during the MF/UF operation and during UF concentration. Presence of such aggregates affected polishing filtration adversely. Borosilicate glass and poly-ether-sulfone membranes were found to pre-filter this material better than nylon, mixed esters of cellulose and polypropylene membranes. Performance of nylon sterilizing grade membranes (0.2-µm) was better than PVDF membranes. Also, performance of PVDF membranes was different for different manufacturers. Increasing pH of the UF concentrate improved polishing filtration for some lots. Presence of bio-burden and air entrainment/foam formation complicated polishing filtration.