Recombinant E. coli for Defined PHA Monomer Composition
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Solution Overview
Problem
Current methods for controlling the repeating unit composition of medium-chain-length (MCL) poly(3-hydroxyalkanoate) (PHA) biopolymers are limited, often resulting in random mixtures with narrow ranges of repeating units, and previous attempts to control synthesis in native or recombinant organisms have failed to achieve broad control beyond a few units or maintain control when the number of carbons exceeds seven.
Innovation Solution
A recombinant Escherichia coli strain, E. coli LSBJ, is engineered by deleting the fadB and fadJ genes from the β-oxidation pathway, allowing for the conversion of enoyl-CoA intermediates to PHAs by an (R)-specific enoyl-CoA hydratase (PhaJ4) and PHA synthase (PhaC1(STQK)), enabling the production of PHAs with repeating units equal in carbon length to the fed fatty acid substrates, thereby achieving strict control over repeating unit composition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional methods are used to control repeating unit composition of MCL PHA, then synthesis control is achieved for a narrow range of repeating units, but control is lost when the number of carbons exceeds seven
Solution Approach 1:
The invention divides the β-oxidation pathway into discrete segments by deleting specific genes (fadB, fadJ, fadL, fadG) to create controlled blockages at specific carbon chain lengths. This segmentation allows independent control of different repeating unit sizes (C4, C6, C8, C10, C12) that would otherwise be interconnected in the natural pathway, resolving the contradiction between precision control and broad adaptability.
Solution Approach 2:
The invention changes the parameters of the β-oxidation pathway by introducing engineered enzymes with specific substrate specificities (PhaJ4 for C4-C6, PhaJ5 for C8-C12) that operate at different stages of the pathway. By adjusting which enzyme is expressed and which pathway genes are deleted, the system can produce PHAs with different repeating unit compositions, achieving both precision and versatility.
2Manufacturing precision
If native or recombinant PHA-producing organisms are used, then some control over repeating units is achieved, but only a limited range of repeating unit sizes can be synthesized
Solution Approach 1:
The engineered E. coli strain serves multiple functions: it can produce different types of PHAs (SCL and MCL) with various repeating unit compositions by simply changing the fatty acid substrate and induced enzyme, rather than requiring different organism strains for each PHA type. This universal platform resolves the contradiction by making one system adaptable to multiple product specifications.
Solution Approach 2:
The invention introduces intermediary enzymes (PhaJ4, PhaJ5) that mediate the conversion of enoyl-CoA intermediates to 3-hydroxyacyl-CoA monomers with specific chain lengths. These intermediaries bridge the gap between the β-oxidation pathway and PHA synthesis, enabling precise control over which carbon chain lengths are incorporated into the polymer, thus achieving both precision and broad range.
3Manufacturing precision
If the β-oxidation pathway is modified to control PHA synthesis, then repeating unit composition can be controlled, but the system becomes more complex
Solution Approach 1:
The invention extracts and removes specific genes (fadB, fadJ, fadL, fadG) from the β-oxidation pathway to eliminate unwanted metabolic branches that would otherwise produce mixed repeating unit compositions. By taking out these interfering elements, the system achieves precise control without requiring complex regulatory mechanisms, resolving the contradiction between precision and simplicity.
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 allows for the production of PHAs with defined repeating unit compositions from four to twelve carbons, spanning both short-chain-length (SCL) and MCL PHAs, providing unprecedented control over a broad range of repeating units, suitable for various applications including medical uses.
Implementation Method 1
converting the enoyl-CoA intermediates PHAs by an (R)-specific enoyl-CoA hydratase (PhaJ4)
Implementation Method 2
PHA synthase (PhaC1(STQK)), enabling the production of PHAs with repeating units equal in carbon length to the fed fatty acid substrates
Data Source
AI summary
Methods and systems for producing prescribed unit size azido-poly(3-hydroxyalkanoate) (azido-PHA) polymers and copolymers are provided. The methods and systems can employ recombinant bacteria that are not native producers of PHA or lack enzymes to degrade PHA once synthesized, metabolize short to long chain fatty acids without induction, and express an (R)-specific enoyl-CoA hydratase and a PHA synthase, the (R)-specific enoyl-CoA hydratase and PHA synthase having wide substrate specificities. The recombinant bacteria are fed at least one ω-azidofatty acid substrate that is equal in carbon length to the prescribed or desired unit size of an azido-PHA polymer to be produced. Azido-PHA polymers or azido-PHA co-polymers can be conjugated via copper-catalyzed alkyne-azide cycloaddition (CuAAC) or strain-promoted azide-alkyne cycloaddition (SPAAC) reactions. The prescribed unit size conjugated azido-PHA polymer or orthogonally conjugated azido-PHA co-polymer that is produced is then isolated and/or purified.