Recombinant Enteric Bacterial Strain for High-Yield L-Tyrosine Production
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Solution Overview
Problem
Current methods for producing tyrosine in microorganisms result in low yields, with the highest reported level being 26 g/l for Corynebacterium glutamicum, limiting its commercial production potential.
Innovation Solution
Engineering a recombinant enteric bacterial strain with disruptions in the pheA gene and over-expression of the tyrA gene using a single insertion method, combined with modifications to the aromatic amino acid pathway, to create a strain that over-produces tyrosine and confers resistance to various chemicals and high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If traditional genetic methods or separate step engineering are used to increase tyrosine production, then tyrosine production levels can be improved, but the production levels remain limited (highest 26 g/l) and the process complexity increases
Solution Approach 1:
The patent combines multiple genetic modifications (pheA disruption and tyrA overexpression) into a single integrated genetic construct that is introduced in one transformation step. This merging of multiple engineering operations into a single unified approach simultaneously achieves high tyrosine production while reducing process complexity compared to traditional multi-step methods.
Solution Approach 2:
The engineered bacterial strain serves multiple functions: it disrupts pheA to eliminate competing pathways, overexpresses tyrA to enhance tyrosine synthesis, and maintains cellular viability and growth. This multi-functional genetic construct achieves several objectives simultaneously, improving tyrosine production without requiring separate engineering steps for each function.
2Quantity of substance
If multiple separate genetic modifications are introduced to achieve high tyrosine production, then tyrosine production can be improved, but the time and number of steps required increases
Solution Approach 1:
The patent designs a pre-assembled genetic construct containing both the pheA disruption and tyrA overexpression elements in a single integrated design. This preliminary preparation of the complete genetic modification package allows for one-step introduction into the bacterial host, eliminating the need for sequential transformation steps and significantly reducing the time required to develop high-producing strains.
Solution Approach 2:
Multiple genetic modifications that would traditionally require separate transformation steps are merged into a single integrated construct. This combining approach allows simultaneous introduction of all necessary genetic changes in one experimental operation, dramatically reducing the time and number of steps compared to traditional sequential engineering approaches.
3Productivity
If pheA expression is increased to enhance aromatic amino acid pathway capacity, then pathway flux is improved, but tyrosine production decreases because chorismate is diverted to phenylalanine
Solution Approach 1:
The patent extracts or removes the competing phenylalanine production pathway by disrupting the pheA gene. This elimination of the competing pathway ensures that chorismate flux through the aromatic amino acid pathway is directed exclusively toward tyrosine production via the overexpressed tyrA enzyme, rather than being diverted to phenylalanine synthesis.
Solution Approach 2:
The patent applies local quality control by specifically modifying the tyrA gene expression level while leaving other pathway enzymes at their native levels. This localized overexpression of tyrA creates a bottleneck effect that channels pathway flux preferentially toward tyrosine production, optimizing the specific metabolic step that determines tyrosine yield without requiring global pathway reengineering.
Data Source
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AI summary
An enteric bacterial strain was engineered to over-produce L-tyrosine using a one-step method. The pheA-tyrA chromosomal region of the bacterial genome was replaced with an engineered chromosomal segment, resulting in inactivation of the pheA coding region and strong expression of the tyrA coding region, resulting in high levels of L-tyrosine production.