Bioreactor Production of Human α1-Antitrypsin Using Metabolically Regulated Plant Cell Cultures

Transgenic rice cell cultures, capable of producing recombinant human α1‐antitrypsin (rAAT), were scaled up from shake flasks to a 5‐L bioreactor. The maximum specific growth rates (μmax) 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 O2/(g dw h). Using a metabolically regulated rice α‐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.