Transcriptional analysis for carbon metabolism and kinetic modeling for heterologous proteins productions by Pichia pastoris in induction process with methanol/sorbitol co-feeding

It is difficult to control concentrations of methanol/dissolved oxygen at high levels simultaneously in heterologous proteins productions by Pichia pastoris during induction phase. Two strains, a methanol utilization slow (MutS) type and a plus (Mut+) type were used with methanol/sorbitol co-feeding strategy to induce porcine interferon-α and human serum albumin-human granulocyte colony stimulating factor respectively, under the conditions of “methanol sufficient-oxygen limited (MS-OL)” and “methanol limited-oxygen sufficient (ML-OS)”. For the MutS/Mut+ strains, the target proteins titers under “MS-OL” were 6-fold/19.2% of those under “ML-OS”. The key genes in methanol metabolism of the MutS strain were up-regulated under “MS-OL”, but they were not differently expressed in the Mut+ strain. Methanol utilization rate (rMeOH) of the MutS strain reduced when decreasing methanol concentration, but rMeOH of the Mut+ strain unchanged unless methanol concentration decreased to a low-limit of 0.6 g/L. Finally, kinetic models were designed to describe the methanol/sorbitol co-feeding process.