Biosynthesis of High Toughness Poly(3-Hydroxypropionate)-Based Block Copolymers With Poly(D-2-Hydroxybutyrate) and...

Area of Science:

• Biotechnology
• Polymer Science
• Materials Science

Background:

• Polyhydroxyalkanoates (PHAs) are biodegradable polyesters with diverse applications.
• Developing novel PHA block copolymers with tailored mechanical properties is crucial for expanding their utility.
• Poly(3-hydroxypropionate) [P(3HP)] is a PHA monomer with potential for creating advanced materials.

Purpose of the Study:

• To synthesize and characterize novel poly(3-hydroxypropionate) [P(3HP)]-containing polyhydroxyalkanoate (PHA) block copolymers.
• To investigate the mechanical properties of P(3HP)-b-P[2-hydroxybutyrate (2HB)] and P(3HP)-b-P(D-lactate) (PDLA) block copolymers.
• To establish structure-property relationships for these novel biomaterials.

Main Methods:

• Engineered Escherichia coli expressing a sequence-regulating PHA synthase (PhaC_ARNDFH) and propionyl-CoA transferase.
• Culturing engineered E. coli with specific monomer precursors to synthesize P(3HP)-b-P(2HB) and P(3HP)-b-PDLA.
• Characterization using proton nuclear magnetic resonance (1H NMR) and solvent fractionation; mechanical testing of polymer films after controlled thermal treatments.

Main Results:

• Successfully synthesized P(3HP)-b-P(2HB) and P(3HP)-b-PDLA block copolymers with molecular weights ranging from 0.8-2.8 × 10⁵.
• Melt-quenched P(3HP)-b-P(2HB) films exhibited high elongation at break (1153%) and toughness (181 MJ/m³).
• P(3HP)-b-PDLA films showed partial elastic deformation, with P(3HP) acting as a soft segment, though high lactate content led to embrittlement upon melt-quenching.

Conclusions:

• P(3HP)-based block copolymers, P(3HP)-b-P(2HB) and P(3HP)-b-PDLA, can be synthesized using engineered E. coli.
• The mechanical properties of these copolymers are highly dependent on their higher-order structure and the P(2-hydroxyalkanoate) segments.
• Precise control over microstructure is key to optimizing the performance of these novel PHA block copolymers for various applications.