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α-Substituted 3-hydroxy acid production from glucose in Escherichia coli
K'yal R Bannister1, Kristala L J Prather1
1Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, 02139, USA.
Metabolic Engineering
|September 23, 2024
Summary
Researchers developed a new microbial pathway to produce alpha-substituted hydroxy acids (HAs) for creating enhanced polyhydroxyalkanoates (PHAs) plastics. This novel approach overcomes limitations of existing methods, enabling the synthesis of more thermally stable and industrially relevant bioplastics.
Area of Science:
- Biotechnology
- Polymer Science
- Metabolic Engineering
Background:
- Polyhydroxyalkanoates (PHAs) are sustainable bioplastics derived from microbial polyesters.
- Improving PHA thermal stability is crucial for expanding their application as plastic alternatives.
- Current methods for producing necessary alpha-substituted hydroxy acid (HA) monomers are limited by the narrow substrate specificity of the reverse beta-oxidation (rBOX) pathway's thiolases.
Purpose of the Study:
- To engineer a novel, thiolase-independent metabolic pathway for producing alpha-substituted HAs.
- To enable the synthesis of thermostable PHAs with improved material properties.
- To demonstrate the feasibility of producing 3-hydroxyisobutyric acid (3HIB) and 3-hydroxy-2-methylbutyric acid (3H2MB) from glucose.
Main Methods:
- Designed and implemented a novel metabolic pathway converting glucose to branched acyl-CoAs.
- Engineered Escherichia coli to produce 3HIB and 3H2MB via the new pathway.
- Optimized the 3H2MB production pathway using a byproduct recycle strategy.
Main Results:
- Successfully produced 3HIB at titers up to 66 ± 5 mg/L and 3H2MB at titers up to 290 ± 40 mg/L from glucose.
- Achieved a 60% increase in 3H2MB titer through pathway optimization and byproduct recycling.
- Demonstrated the production of key monomers for advanced PHA synthesis.
Conclusions:
- A novel thiolase-independent pathway enables the microbial production of alpha-substituted HAs.
- This pathway provides a viable route to monomers for creating thermostable PHAs.
- The engineered Escherichia coli strains and optimized pathway offer a promising platform for producing advanced bioplastics with industrially relevant properties.
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