Abstract
BackgroundThe methylotrophic yeast Pichia pastoris is a well-studied host organism for recombinant protein production, which is usually regulated either by a constitutive promoter (e.g. promoter of glyceraldehyde-3-phosphate dehydrogenase; PGAP) or an inducible promoter (e.g. promoter of alcohol oxidase 1; PAOX1). Both promoter systems have several advantages and disadvantages; with one of the main disadvantages being their lack of tunability. Various novel promoter systems, which are either inducible or de-repressed, allowing higher degrees of freedom, have been reported. Recently, bi-directional promoter systems in P. pastoris with two promoter systems regulating recombinant expression of one or more genes were developed. In this study, we introduce a novel bi-directional promoter system combining a modified catalase promoter system (PDC; derepressible and inducible) and the traditional PAOX1, allowing tunable recombinant protein production.ResultsWe characterized a recombinant P. pastoris strain, carrying the novel bi-directional promoter system, during growth and production in three dynamic bioreactor cultivations. We cloned the model enzyme cellobiohydralase downstream of either promoter and applied different feeding strategies to determine the physiological boundaries of the strain. We succeeded in demonstrating tunability of recombinant protein production solely in response to the different feeding strategies and identified a mixed feed regime allowing highest productivity.ConclusionIn this feasibility study, we present the first controlled bioreactor experiments with a recombinant P. pastoris strain carrying a novel bi-directional promotor combination of a catalase promoter variant (PDC) and the traditional PAOX1. We demonstrated that this bi-directional promoter system allows tunable recombinant protein expression only in response to the available C-sources. This bi-directional promoter system offers a high degree of freedom for bioprocess design and development, making bi-directional promoters in P. pastoris highly attractive for recombinant protein production.
Highlights
IntroductionThe methylotrophic yeast Pichia pastoris is a well-studied host organism for recombinant protein production, which is usually regulated either by a constitutive promoter (e.g. promoter of glyceraldehyde-3-phosphate dehydrogenase; glyceraldehyde-3-phosphate dehydrogenase promoter (PGAP)) or an inducible promoter (e.g. promoter of alcohol oxidase 1; alcohol oxidase promoter (PAOX1))
The methylotrophic yeast Pichia pastoris is a well-studied host organism for recombinant protein production, which is usually regulated either by a constitutive promoter or an inducible promoter
We present our results with respect to the characterization of a novel bi-directional promoter system, where we combined this novel catalase promoter variant (PDC) variant and P AOX1 in a bi-directional manner
Summary
The methylotrophic yeast Pichia pastoris is a well-studied host organism for recombinant protein production, which is usually regulated either by a constitutive promoter (e.g. promoter of glyceraldehyde-3-phosphate dehydrogenase; PGAP) or an inducible promoter (e.g. promoter of alcohol oxidase 1; PAOX1). Both promoter systems have several advantages and disadvantages; with one of the main disadvantages being their lack of tunability. We introduce a novel bi-directional promoter system combining a modified catalase promoter system (PDC; derepressible and inducible) and the traditional P AOX1, allowing tunable recombinant protein production. Apart from the fact that methanol makes the fermentation process dangerous and environmentally non-friendly, methanol metabolism leads to great heat evolution and high oxygen consumption, which pose additional challenges for cultivations at large scales
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