Engineering Access to Stereoirregular Polymer Microstructures Enables Improved Processability of Microbial...

Area of Science:

• Biopolymer Science
• Microbial Engineering
• Polymer Chemistry

Background:

• Poly(3-hydroxybutyrate) (PHB) is a biocompatible and biodegradable polyhydroxyalkanoate.
• Its highly regular stereochemistry leads to high crystallinity and poor processability.
• Current understanding suggests PHA synthases are strictly stereospecific, limiting PHB microstructure diversity.

Purpose of the Study:

• To demonstrate microbial production of stereoirregular PHB.
• To challenge the notion of strict stereospecificity in PHA synthase.
• To explore the impact of stereochemical diversity on PHB properties.

Main Methods:

• Microbial fermentation to produce PHB.
• Characterization of stereochemical composition (e.g., (S)-3-hydroxybutyrate content, m-dyad fraction).
• Thermal analysis (melting temperature) and processing stability assessment.

Main Results:

• Successfully produced stereoirregular PHB with 6.84% (S)-3-hydroxybutyrate and 11.8% m-dyad fraction.
• Stereoirregular PHB exhibited a reduced melting temperature (154.3 °C) compared to conventional PHB (179.3 °C).
• The stereoirregular material showed decreased molar-mass decomposition during processing.

Conclusions:

• Microbial synthesis can produce stereochemically diverse PHB, overcoming assumed limitations of PHA synthase stereospecificity.
• Biologically produced stereoirregular PHB offers improved processability and recyclability, similar to chemically synthesized analogues.
• This work provides a foundation for microbial engineering to tune polymer microstructure and performance.