A simple unstructured model-based control for efficient expression of recombinant porcine insulin precursor by Pichia pastoris

Based on the fact that Pichia cell growth follows a Monod equation under the condition of methanol concentration limitation, a kinetics model of recombinant methylotrophic yeast Pichia pastoris expressing porcine insulin precursor (PIP) was developed in the quasi-steady state in the induction phase. The model revealed that the relationship between specific growth rate (μ) and substrate methanol concentration was in accord with the Monod equation. The fermentation kinetic parameters maximum specific growth rate (μ _max ), saturation constant (K _s ) and maintenance coefficient (M) were estimated to be 0.101 h⁻¹, 0.252 g l ⁻¹, and 0.011 g MeOH g⁻¹ DCW h⁻¹, respectively. The unstructured model was validated in methanol induction phase with different initial cell densities. Results showed that the maximum specific protein production rate (q _p.max ) of 0.098 mg g⁻¹ DCW h⁻¹ was achieved when μ was kept at 0.016 h⁻¹, and the maximum yield of PIP reached 0.97 g l ⁻¹, which was 1.5-fold as that of the control. Therefore, the simple Monod model proposed has proven to be a robust control system for recombinant porcine insulin precursor production by P. pastoris on pilot scale, which would be further applied on production scale. This work was presented at 13 ^th YABEC symposium held at Seoul, Korea, October 20–22, 2007.