Recombinant β‐Galactosidase Production in Serum‐Free Medium by Insect Cells in a 14‐L Airlift Bioreactor

Spodoptera frugiperda (Sf9) insect cells were successfully cultured in serum‐free medium in a 14‐L airlift bioreactor. Cell densities as high as 1 × 10 7 cells/mL were achieved with specific growth rates of approximately 0.0286 h −1 (doubling time of 24 h). This system was also used to demonstrate the expression of a reported gene, β‐galactosidase (β‐gal), when cells were infected with a recombinant baculovirus. Approximately 0.33 mg of β‐gal/mL (i.e., 104 000 units/mL) of medium were obtained at the 14‐L scale, while about 0.95 mg of β‐gal/mL (i.e., 285 000 units/mL) of medium were obtained in small‐scale shaker flasks. The difference was attributed to a suboptimal infection in the large scale. Specific oxygen consumption rates decreased from 5.58 × 10 −17 mol O 2 cell·s in early exponential growth to 3.13 × 10 −17 mol (O 2 cell·s at 3 days post‐infection.