Development of a dual specific growth rate-based fed-batch process for production of recombinant human granulocyte colony-stimulating factor in Pichia pastoris.

A number of limitations exist for production of human granulocyte colony-stimulating factor (G-CSF) in Pichia pastoris. In this study, two different specific growth rates (0.015 h, 0.01 h) were used sequentially in the mixed substrate feeding period during methanol induction phase to enhance the G-CSF titer in the culture broth. Necessary parameters required for implementing the feeding strategy, such as specific product yield on biomass (Y) and maintenance coefficient (m) on glycerol, methanol, and sorbitol were estimated using continuous culture technique. Using this strategy, for the same volumetric productivity, about 20% increase in protein titer was achieved over that obtained from the run carried out at a single pre-set value of 0.015 h alone. Thus, implementation of higher specific growth rate (0.015 h) set during initial stages of the methanol induction phase followed by a lower specific growth rate (0.01 h) helped in achieving increased protein titers.