Controlled Feeding Facilitates the Development of a Robust Production Process for Terpolymeric Polyhydroxyalkanoates.

Area of Science:

• Biotechnology and Biopolymer Production
• Microbial Fermentation and Bioprocess Engineering
• Sustainable Materials Science

Background:

• Polyhydroxyalkanoates (PHAs) are biodegradable biopolymers with potential for sustainable applications.
• Limited availability and material properties restrict current PHA usage.
• Novel PHA variants like terpolymers offer opportunities for enhanced material characteristics.

Purpose of the Study:

• To report the production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-4-hydroxyvalerate) (PHBVV) terpolymer with high 3-hydroxyvalerate (3HV) content.
• To implement and validate a controlled feeding strategy for levulinic acid in bioreactors.
• To demonstrate the scalability of PHBVV production in stirred tank bioreactors.

Main Methods:

• Utilized Cupriavidus necator for terpolymer production.
• Implemented a fully controlled feeding strategy based on pH and pO2 signals for levulinic acid delivery.
• Validated the process in 7.5-L and 42-L bioreactors.

Main Results:

• Achieved a maximum biomass of 40.2 g L⁻¹ with 75% PHA content (dry cell weight).
• Obtained a PHA yield of 0.32 gPHA gLA⁻¹.
• Successfully produced PHBVV terpolymers with 38%-46% 3HV and 1%-2% 4HV content at both scales.

Conclusions:

• Demonstrated a scalable and automated method for PHBVV terpolymer production.
• Provided a comprehensive dataset for optimizing PHA bioprocesses.
• Established a framework for the industrial production of novel PHA variants with tailored properties.