Stabilizing porcine interferon-α production byPichia pastoriswith an ethanol on-line measurement based DO-Stat glycerol feeding strategy

BACKGROUND Achievement of very high cell concentration is the prerequisite for enhanced porcine interferon-α (pIFN-α) production by Pichia pastoris, but it is closely associated with severe ethanol accumulation, leading to instability in pIFN-α expression. RESULTS By analyzing the transcriptional levels of genes encoding the key enzymes in methanol metabolism, it was found that high (more than 6 g L−1) and long term (more than 4 h) ethanol accumulation in the late glycerol feeding cultivation phase irreversibly repressed alcohol oxidase (AOX) promoter, leading to instability in pIFN-α production. A novel improved DO-Stat glycerol feeding strategy based on on-line ethanol measurement was thus proposed to control ethanol concentration at a low level of 2 g L−1, while maintaining cell growth at comparably high level. With the aid of the proposed strategy, maximum pIFN-α concentration increased 29.8–75.5% compared with the best one adopting the 'traditional' DO-Stat strategy, when the same methanol induction strategy (methanol/sorbitol co-feeding ratio of 1:1) was applied. CONCLUSION The proposed improved DO-Stat strategy is effective in simultaneously achieving very high concentration of the cells with functional cellular skeletons and repressing ethanol accumulation in the glycerol feeding phase, which enhanced and stabilized pIFN-α production during the induction condition in turn. © 2013 Society of Chemical Industry