Burden-Addiction Genetic Circuit for Stable Microbial Production
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Solution Overview
Problem
Non-producing cells in microbial cell factories gain a selective advantage over producing cells due to slower growth, leading to a decline in productivity and the need for frequent tank replenishment, as they consume resources and outcompete producing cells.
Innovation Solution
Genetically engineer microbial production cells with an essential gene linked to a burden-sensing promoter that up-regulates expression when the cell experiences a burden or fitness cost, independent of the product itself, to maintain productivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If cells are engineered to allocate finite metabolic resources to biosynthesis of a given molecule, then productivity is improved, but growth rate deteriorates
Solution Approach 1:
The patent changes the regulatory parameters of essential genes by linking them to burden-sensing promoters that respond to metabolic burden. This allows dynamic adjustment of gene expression levels based on the cell's physiological state, enabling the cell to maintain adequate growth while allocating resources to product synthesis when needed.
Solution Approach 2:
The patent implements a feedback mechanism where the metabolic burden experienced by the cell during product synthesis is sensed and used to up-regulate the expression of essential genes. This feedback loop ensures that cells under high production burden receive additional support for essential functions, maintaining overall cellular fitness and productivity.
2Productivity
If production run is extended over time, then productivity is improved, but selective pressure for non-producing cells increases
Solution Approach 1:
The burden-sensing promoter system provides continuous feedback during extended production runs, dynamically adjusting essential gene expression based on real-time metabolic burden. This prevents the accumulation of non-producing cells by ensuring that producing cells maintain a growth advantage throughout the entire production run, thereby maintaining population stability over time.
Solution Approach 2:
The patent prepares the cell population for extended production by pre-establishing the burden-sensing regulatory system before production begins. This preliminary configuration ensures that when non-producing cells attempt to emerge during extended runs, the selective pressure mechanism is already in place to suppress their proliferation, maintaining population integrity throughout the extended production period.
3Speed
If non-producing cells are allowed to proliferate, then growth rate is improved, but productivity deteriorates
Solution Approach 1:
The patent converts the harmful metabolic burden of product synthesis into a beneficial selective advantage. By linking essential gene expression to burden-sensing promoters, the metabolic burden experienced during product synthesis triggers up-regulation of essential genes, which in turn enhances the growth and survival of producing cells. This transforms what was previously a disadvantage (slower growth due to burden) into a benefit (selective advantage for producing cells).
Data Source
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AI summary
The invention provides a microbial production cell for synthesis of a product, further comprising a burden-addiction genetic circuit whose expression confers a selective growth and/or survival advantage on those cells that synthesize the product; while limiting proliferation of low- or non-productive escaper cells.