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Biosynthesis of polylactic acid and its copolymers using evolved propionate CoA transferase and PHA synthase
Taek Ho Yang1, Tae Wan Kim, Hye Ok Kang
1Corporate R&D, LG Chem Research Park, 104-1 Moonji-dong, Yuseong-gu, Daejeon 305-380, Republic of Korea.
Biotechnology and Bioengineering
|November 26, 2009
Summary
Engineered E. coli can now produce polylactic acid (PLA) copolymers via one-step fermentation. This breakthrough enables controlled synthesis of poly(3-hydroxybutyrate-co-lactate) with varying lactate content.
Area of Science:
- Biotechnology
- Metabolic Engineering
- Polymer Science
Background:
- Polylactic acid (PLA) and its copolymers are valuable bioplastics.
- Current synthesis methods can be complex and inefficient.
- Developing microbial platforms for direct biopolymer production is highly desirable.
Purpose of the Study:
- To engineer Escherichia coli for the one-step fermentation synthesis of polylactic acid (PLA) and its copolymers.
- To improve the efficiency of lactyl-CoA generation and its incorporation into polymers.
- To control the composition and properties of the resulting polyhydroxyalkanoate (PHA) copolymers.
Main Methods:
- Introduction of heterologous genes encoding Clostridium propionicum propionate CoA transferase (Pct(Cp)) and Pseudomonas sp. MBEL 6-19 polyhydroxyalkanoate (PHA) synthase 1 (PhaC1(Ps6-19)) into E. coli.
- Enzyme engineering via site-directed, saturation, and random mutagenesis to enhance Pct(Cp) and PhaC1(Ps6-19) activity and substrate acceptance.
- Metabolic pathway engineering by introducing Cupriavidus necator beta-ketothiolase and acetoacetyl-CoA reductase genes.
- Fermentation process optimization, including fed-batch cultures, to control copolymer composition.
Main Results:
- Engineered E. coli produced poly(3-hydroxybutyrate-co-lactate) (P(3HB-co-LA)) containing 20-49 mol% lactate, reaching up to 62 wt% from glucose and 3-hydroxybutyrate (3HB).
- Homopolymer PLA and P(3HB-co-LA) with lactate as the major component were synthesized by controlling 3HB concentration.
- P(3HB-co-LA) copolymers with 9-64 mol% lactate were produced from glucose alone.
- Characterization of copolymer molecular weights, thermal properties, and melt flow properties was performed.
Conclusions:
- Successful engineering of E. coli enables efficient one-step fermentation for PLA and P(3HB-co-LA) synthesis.
- Enzyme and metabolic pathway engineering are critical for producing tailored biopolymers.
- The developed microbial platform offers a versatile route to biodegradable polymers with tunable properties.
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