Identifying bottleneck reactions and developing a systemic fed-batch
feeding strategy of Pichia pastoris through fine-tuning of methanol
utilization pathway
Abstract
Pichia pastoris as an efficient host for the production of recombinant
proteins is mostly cultivated in fed-batch mode in which the cell’s
environment is continuously changing. Therefore, to fine-tune bioreactor
performance in respect to the associated metabolic changes of the
microorganism, it is crucial to understand the influence of feeding
strategy parameters on the intracellular reaction network. In this
study, dynamic flux balance analysis (DFBA) integrated with
transcriptomics data was used to simulate the recombinant P.pastoris
(Muts) growth during induction phase for 3 fed-batch µ-stat strategies.
The induction phase was divided into equal time intervals and the
correlated reactions with protein yield were identified in the 3
fed-batch strategies using the Pearson correlation coefficient.
Subsequently, Principal Component Analysis was applied to cluster
induction phase time intervals and identify the role of correlated
reactions on metabolic differentiation of time intervals. It was found
that increasing fluxes through the methanol dissimilation pathway
increased protein yield. By adding a methanol assimilation pathway
inhibitor (HgCl2) to the shake flask medium containing 10% (v/v)
glycerol, the protein titer increased by 60%. Using the DFBA revealed
that the higher the dimensionless flux of methanol, the higher amounts
of protein yield. Finally, a novel feeding strategy was developed so
that the dimensionless methanol flux increased compared to the performed
cultivations. Protein titer increased by 16% compared to the optimally
performed cultivation, while production yield increased by 85%.