Bioreactor production of human α1-antitrypsin using metabolically regulated plant cell cultures

Transgenic rice cell cultures, capable of producing recombinant human alpha(1)-antitrypsin (rAAT), were scaled up from shake flasks to a 5-L bioreactor. The maximum specific growth rates (mu(max)) observed from two bioreactor runs were 0.40 day(-1) (doubling time of 1.7 days) and 0.47 day(-1) (doubling time of 1.5 days), and the maximum specific oxygen uptake rates were 0.78 and 0.84 mmol O-2/(g dw h). Using a metabolically regulated rice alpha-amylase (RAmy3D) promoter, signal peptide, and terminator, sugar deprivation turned on rAAT expression, and rAAT was secreted into the culture medium. After 1 day of culture in sugar-free medium, there was still continued biomass growth, oxygen consumption, and viability. Extracellular concentrations of 51 and 40 mg active rAAT/L were reached 1.7 and 2.5 days, respectively, after induction in a sugar-free medium. Volumetric productivities for two batch cultures were 7.3 and 4.6 mg rAAT/(L day), and specific productivities were 3.2 and 1.6 mg rAAT/(g dw day). Several different molecular weight bands of immunoreactive rAAT were observed on immunoblots.