Two-stage continuous process development for the production of medium-chain-length poly(3-hydroxyalkanoates).

Area of Science:

• Microbial Biotechnology
• Biopolymer Production
• Chemical Engineering

Background:

• Pseudomonas oleovorans produces medium-chain-length poly(3-hydroxyalkanoate) (PHA), a valuable biopolymer.
• PHA accumulation is most effective at sub-maximal growth rates, a process that can be time-consuming.
• Continuous cultivation systems offer potential for efficient PHA production.

Purpose of the Study:

• To optimize a two-stage continuous cultivation system for enhanced PHA production by Pseudomonas oleovorans.
• To investigate the impact of dilution rates, temperature, pH, nutrient limitation, and carbon source on PHA productivity.
• To determine the maximum volumetric PHA productivity and PHA content achievable.

Main Methods:

• Utilized a two-stage continuous fermentation system with fermentors in series.
• Conducted transient-state experiments to investigate dilution rates (D1 and D2) across a wide range.
• Optimized culture parameters including temperature, pH, nutrient limitation, and carbon source.

Main Results:

• Identified optimal dilution rates of 0.21 h⁻¹ (D1) and 0.16 h⁻¹ (D2) for highest volumetric PHA productivity.
• Achieved a maximum volumetric PHA productivity of 1.06 g L⁻¹ h⁻¹.
• Reached a PHA content of 63% (dry weight) in P. oleovorans cells.

Conclusions:

• A two-stage continuous cultivation system is effective for high-yield PHA production.
• Optimized culture parameters significantly enhance PHA productivity and cellular content in P. oleovorans.
• This study reports record PHA productivity and content for P. oleovorans grown on alkanes.