Recombinant Bacterial Host Cell Auto-Induction
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Solution Overview
Problem
Current methods for producing heterologous polypeptides in recombinant bacterial host cells face challenges due to the need for continuous supplementation of inducing substrates, which increases costs and requires expensive inducers, as the promoter deactivates in the absence of the substrate, leading to unintended stoppage of gene expression.
Innovation Solution
A recombinant bacterial host cell system is developed where the promoter regulating the expression of secondary carbon sources is controlled by carbon catabolite repression, allowing expression to continue independently of the inducing carbon source, using a phosphoenolpyruvate: carbohydrate phosphotransferase system and genetic alterations to prevent deactivation of transcriptional regulators, enabling auto-induction when primary carbon sources become limiting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a strong inducible promoter is used to control heterologous polypeptide expression, then high-level expression can be achieved upon induction, but the promoter deactivates when the inducing substrate is depleted, causing unwanted stoppage of gene expression
Solution Approach 1:
The patent extracts the transcriptional regulator gene from the chromosomal locus and relocates it to the expression vector under control of a constitutive promoter. This separation removes the regulator from dependency on the inducible promoter, allowing continuous regulator production and thus continuous expression capability while maintaining high-level production when induced.
Solution Approach 2:
The patent introduces a constitutive promoter as an intermediary element that drives continuous expression of the transcriptional regulator, independent of the inducible substrate. This intermediary ensures steady supply of the regulator protein, enabling the system to maintain expression capability regardless of inducer presence.
2Reliability
If high amounts of inducer are continuously supplemented to maintain promoter activity, then gene expression can be maintained, but the costs of the fermentation process increase significantly
Solution Approach 1:
The patent performs preliminary action by placing the transcriptional regulator under a constitutive promoter in the vector, ensuring the regulator is continuously produced and ready to activate the heterologous gene expression without waiting for inducer addition. This preliminary preparation of the regulatory mechanism eliminates the need for continuous inducer supplementation.
3Productivity
If expensive inducers are used to control efficient promoters, then high-level polypeptide production is achieved, but the production costs increase
Solution Approach 1:
The patent extracts the transcriptional regulator from chromosomal control and places it under constitutive promoter control in the vector, eliminating the need for expensive inducers. The regulator is now continuously produced, making the expression system independent of costly inducer addition while maintaining high production efficiency.
4Quantity of substance
If the promoter is made independent from inducer presence for continuous expression, then induction costs are reduced, but tight regulation of heterologous polypeptide expression becomes difficult
Solution Approach 1:
The patent segments the expression system into two independent functional modules: (1) a constitutive promoter driving continuous regulator production, and (2) an inducible promoter controlling heterologous gene expression. This segmentation allows the regulator to be continuously available while the actual expression remains tightly regulated by the inducible promoter, maintaining ease of operation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach eliminates the need for continuous inducer supplementation, reduces production costs, and allows for high-density fermentation with controlled expression of heterologous polypeptides without requiring an inducing carbon source, ensuring consistent production.
Implementation Method 1
carbon catabolism of these carbon sources of the bacterial host cell is subjected to the phosphoenolpyruvate: carbohydrate phosphotransferase system
Implementation Method 2
the promoter is solely under control of carbon catabolite repression
Data Source
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AI summary
The present invention relates to the production of heterologous polypeptides in a recombinant bacterial host cell, wherein the bacterial host cell is rendered inable to deactivate the promoter controlling the expression of the heterologous polypeptide in the absence of an inducer.