Perfusion bioreactors for the production of recombinant proteins in insect cells

High density perfusion culture of insect cells for the production of recombinant proteins has proved to be an attractive alternative to batch and fed-batch processes. A comparison of the different production processes is summarized in Table 3. Internal membrane perfusion has a limited scale-up potential but appears to the method of choice in smaller lab-scale production systems. External membrane perfusion results in increased shear stress generated by pumping of cells and passing through microfiltration modules at high velocity. However, using optimized perfusion strategies this shear stress can be minimized such that it is tolerated by the cells. In these cases, perfusion culture has proven to be superior to batch production with respect to product yields and cell specific productivity. Although insect cells could be successfully cultivated by immobilization and perfusion in stationary bed bioreactors, this method has not yet been used in continuous processes. In fluidized bed bioreactors with continuous medium exchange cells showed reduced growth and protein production rates.For the cultivation of insect cells in batch and fedbatch processes numerous efforts have been made to optimize the culture medium in order to allow growth and production at higher cell densities. These improved media could be used in combination with a perfusion process, thus allowing substantially increased cell densities without raising the medium exchange rate. However, sufficient oxygen supply has to be guaranteed during fermentation in order to ensure optimal productivity.