Microbial synthesis of polyhydroxyalkanoate blends with engineered Pseudomonas putida

Area of Science:

• Biotechnology
• Polymer Science
• Microbial Engineering

Background:

• Polyhydroxyalkanoates (PHAs) are biodegradable biopolymers serving as sustainable alternatives to petroleum-based plastics.
• Current PHA production often involves post-synthesis blending, requiring multiple fermentation and extraction steps.
• Direct synthesis of PHA blends offers a more efficient and streamlined production pathway.

Purpose of the Study:

• To engineer Pseudomonas putida for the direct microbial synthesis of poly-3-hydroxybutyrate [P3(HB)] and medium-chain-length PHA (mcl-PHA) blends.
• To control the composition of PHA blends by utilizing different promoter strengths.
• To evaluate the feasibility of one-step biomanufacturing of customizable PHA blends.

Main Methods:

• Genetic engineering of Pseudomonas putida to co-produce P3(HB) and mcl-PHA.
• Utilizing various promoters to modulate the monomer composition of the PHA blends.
• Optimizing fermentation conditions for maximal PHA yield and content.
• Characterization of PHA blends using gel permeation chromatography, nuclear magnetic resonance, and diffusion ordered spectroscopy.

Main Results:

• Successfully produced PHA blends with 3HB monomer content ranging from 17.9 to 99.6 mol%.
• Achieved a maximum PHA production of 1.48 g/L with 52.2 wt% PHA content.
• Confirmed higher molecular weight for P(3HB) compared to mcl-PHA in all blends.
• Synthesized PHA blends exhibited thermal properties comparable to those produced via melt compounding.

Conclusions:

• Demonstrated the microbial synthesis of PHA blends in Pseudomonas putida.
• Established promoter selection as a method for controlling PHA blend composition during fermentation.
• Paved the way for the one-step biomanufacturing of tailored PHA blends, enhancing sustainability in bioplastics.