Long-term Continuous Production of Monoclonal Antibody by Hybridoma Cells Immobilized in a Fibrous-Bed Bioreactor

The kinetics and long-term stability of continuous production of monoclonal antibody IgG2b by hybridoma HD-24 cells immobilized in a fibrous-bed bioreactor (FBB) were studied for a period of ∼8 months. The cells were immobilized in the fibrous bed by surface attachment of cells and entrapment of large cell clumps in the void space of the fibrous matrix. A high viable cell density of 1.01 × 108/ml was attained in the bioreactor, which was about 63 times higher than those in conventional T-flask and spinner flask cultures. The continuous FBB produced IgG at a concentration of ∼0.5 g/l, with reactor productivity of ∼7 mg/h·l, which was about 23 times higher than those from conventional T-flask and spinner flask cultures. The IgG concentration can be further increased to ∼0.67 g/l by using higher feed (glucose and glutamine) concentrations and running the reactor at a recycle batch or fed-batch mode. The long-term performance of this bioreactor was also evaluated. For a period of 36 days monitored, the MAb produced in the continuous well-mixed bioreactor at 50 h retention time (0.02/h dilution rate) was maintained at a steady concentration level of ∼0.3 g/l with less than 8% drift. At the end of the study, it was found that ∼25% of the cells were strongly attached to the fiber surfaces and the other ∼75% entrapped or weakly immobilized in the fibrous matrix. The strongly attached cells had a high viability of ∼90%, compared to ∼75% for cells weakly immobilized and only ∼1.4% for freely suspended cells, suggesting that the fibrous matrix preferentially retained and protected the viable (productive) cells. The FBB thus was able to maintain its long-term productivity because nonviable and dead cells were continuously washed off from the fibrous matrix. The high MAb concentration and production rate and excellent stability for continuous long-term production obtained in this study compare favorably to other bioreactor studies reported in the literature. The reactor performance can be further improved by providing better pH and aeration controls at higher feed concentrations. The FBB is easy to operate and scale-up, and thus can be used economically for industrial production of MAb.