R-Hydratase Gene for High 3HHx PHA Production
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Solution Overview
Problem
Current methods for microbially producing poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) with high 3HHx fraction and high growth ability are hindered by low 3HHx content and reduced growth capacity in recombinant strains, particularly when using vegetable oils as carbon sources.
Innovation Solution
Introduction of a R-hydratase gene into a recombinant Cupriavidus necator strain to convert intermediates in the fatty acid β-oxidation system to (R)-3-hydroxyacyl-CoA monomers, enabling the production of P(3HB-co-3HHx) with a high 3HHx fraction and maintaining high growth ability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If phaC Ac (PHA synthase from A. caviae) is introduced into C. necator to produce P(3HB-co-3HHx) from vegetable oils, then PHA accumulation ability is improved, but 3HHx fraction decreases to 4-5 mol%
Solution Approach 1:
The patent introduces phaJ Ac (R-hydratase gene) as an intermediary enzyme that converts enoyl-CoA intermediates to (R)-3-hydroxyacyl-CoA monomers, which then serve as substrates for phaC Ac to synthesize P(3HB-co-3HHx) with improved 3HHx fraction while maintaining high PHA accumulation
Solution Approach 2:
The patent performs preliminary conversion of enoyl-CoA to (R)-3-hydroxyacyl-CoA monomers before polymerization by phaC Ac, ensuring the availability of appropriate monomer substrates with correct stereochemistry to achieve high 3HHx fraction in the final copolymer
2Productivity
If phaC Ac is introduced into PHB-4 strain to produce P(3HB-co-3HHx), then PHA accumulation is improved, but growth ability is reduced
Solution Approach 1:
The patent changes the metabolic pathway parameters by introducing phaJ Ac to optimize the supply of (R)-3-hydroxyacyl-CoA monomers, allowing the system to achieve high PHA accumulation with maintained growth ability through improved metabolic efficiency rather than burdening the cell with excessive foreign gene expression
3Adaptability or versatility
If 3HHx fraction is increased to improve polymer flexibility, then polymer flexibility is improved, but PHA content may decrease
Solution Approach 1:
The patent optimizes the 3HHx fraction parameter to 7-15 mol% range, which provides sufficient polymer flexibility while maintaining high PHA content through efficient metabolic flux directed by the introduced phaJ Ac and phaC Ac genes
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
The method achieves a 3HHx fraction of 5-20 mol% and a P(3HB-co-3HHx) content of 50-90% by weight, enhancing PHA productivity and flexibility while maintaining high growth ability.
Implementation Method 1
phaJ AC , a gene located immediately downstream to PHA synthase, encodes (R)-form-specific enoyl-CoA hydratase (hereinafter referred to simply as 'R-hydratase') that converts enoyl-CoA, an intermediate in the fatty acid β-oxidation system, to (R)-3HA-CoA
Data Source
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AI summary
Summary The present invention intends to produce poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) [P(3HB-co-3HHx)] with a high 3-hydroxyhexanoic acid fraction using a vegetable oil as a basic raw material. In accordance with the present invention, there is provided a method of producing a microorganism that produces poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) with a high 3-hydroxyhexanoic acid fraction using a vegetable oil as a basic raw material, by introducing a gene encoding R-hydratase that converts a fatty acid β-oxidation system intermediate to a monomer, (R)-3-hydroxyacyl-CoA [R-3HA-CoA], into a recombinant Cupriavidus necator strain that was conferred an ability of producing P(3HB-co-3HHx).