Versatile aliphatic polyester biosynthesis system for producing random and block copolymers composed of 2-, 3-, 4-,...

Area of Science:

• Biotechnology
• Polymer Science
• Microbial Engineering

Background:

• Polyhydroxyalkanoates (PHAs) are microbial polyesters with random monomer sequences in natural copolymers.
• The novel PHA synthase PhaC_AR enables the biosynthesis of PHA block copolymers.
• Understanding monomer sequence determinants is crucial for designing tailored PHA materials.

Purpose of the Study:

• To explore the substrate scope of the sequence-regulating PHA synthase PhaC_AR.
• To identify the determinants of monomer sequence in PHA copolymers synthesized by PhaC_AR.
• To investigate the potential for designing PHA block copolymers with specific sequences.

Main Methods:

• Utilized recombinant Escherichia coli expressing PhaC_AR, CoA transferase, and CoA ligase.
• Cultured engineered E. coli in media supplemented with various hydroxyalkanoate (HA) monomers.
• Analyzed PHA composition and sequence using techniques including differential scanning calorimetry.

Main Results:

• PhaC_AR demonstrated a broad substrate scope, incorporating 2-, 3-, 4-, 5-, and 6-hydroxyalkanoates.
• Homopolymers of 3-hydroxybutyrate (3HB) and 3-hydroxypropionate (3HP) were produced, and they copolymerized randomly.
• Block copolymers were synthesized when 2-hydroxybutyrate (2HB) was present, specifically P(3HP)-b-P(2HB) and P(3HB-co-LMC HA)-b-P(2HB).

Conclusions:

• 3HB or 3HP units are essential for PhaC_AR-mediated PHA synthesis.
• The presence of 2HB is critical for the formation of PHA block copolymers.
• This research provides insights into PhaC_AR's sequence regulation mechanism, enabling the design of novel PHA block copolymers.