High-Level Production of Short- and Medium-Chain-Length Polyhydroxyalkanoates from Glucose Using Metabolically...

Area of Science:

• Biotechnology
• Metabolic Engineering
• Polymer Science

Background:

• Growing demand for bio-based and biodegradable plastics drives interest in polyhydroxyalkanoates (PHAs).
• Short- and medium-chain-length (SCL-MCL)-PHA copolymers offer enhanced flexibility and thermal properties.
• Challenges exist in high-level PHA production from inexpensive carbon sources like glucose due to precursor supply and polymerization inefficiencies.

Purpose of the Study:

• To achieve high-level de novo production of SCL-MCL-PHAs from glucose using metabolically engineered Escherichia coli.
• To develop a modular metabolic engineering strategy for efficient SCL-MCL-PHA synthesis.

Main Methods:

• Engineered E. coli using a three-module strategy: 3-hydroxybutyryl-CoA monomer pathway construction, enhanced fatty acid biosynthesis for MCL-fatty acyl-CoA supply, and screening of broad-substrate-specificity PHA synthases.
• Identified PHA synthase (PhaC) variants from Pseudomonas sp. MBEL 6-19 for efficient polymerization of both SCL and MCL monomers.
• Utilized fed-batch cultures for PHA production and analysis of SCL-MCL-PHA yields and MCL fractions.

Main Results:

• Engineered strains achieved high-level SCL-MCL-PHA production from glucose.
• One strain produced 82.88 g L^-1 PHA with 5 mol% MCL fraction, while another yielded 17.35 g L^-1 PHA with 19.52 mol% MCL fraction.
• Achieved MCL fractions (5-20 mol%) are suitable for various polymer applications, indicating industrial relevance.

Conclusions:

• A modular metabolic engineering approach enables efficient, tunable, and sustainable production of SCL-MCL-PHAs from glucose.
• The identified PHA synthase variants are key to polymerizing both SCL and MCL monomers effectively.
• This strategy provides a versatile framework for industrial-scale bioplastic production.