Selective recovery of polyhydroxyalkanoate inclusion bodies from fermentation broth by dissolved-air flotation

Area of Science:

• Biotechnology
• Bioprocess Engineering
• Separation Science

Background:

• Polyhydroxyalkanoates (PHAs) are biopolyesters with diverse applications.
• Efficient separation of PHA inclusion bodies from cellular debris is crucial for downstream processing.
• Pseudomonas putida is a common host for PHA production.

Purpose of the Study:

• Investigate selective dissolved-air flotation for PHA inclusion body separation.
• Determine optimal conditions for separating PHA inclusion bodies from P. putida cell debris.
• Understand the interaction forces governing PHA inclusion body aggregation.

Main Methods:

• Dissolved-air flotation (DAF) was employed for separation.
• Iso-electric point determination for PHA inclusion bodies and cell debris.
• Analysis of aggregation behavior near the iso-electric point.
• Evaluation of Van der Waals, hydrophobic, and electrostatic interactions.

Main Results:

• Both PHA inclusion bodies and P. putida cell debris exhibit an iso-electric point around pH 3.5.
• Selective aggregation and flotation of PHA inclusion bodies were observed near pH 3.5.
• Standard interaction forces partially explained aggregation, but not always.

Conclusions:

• Selective flotation is a viable method for separating PHA inclusion bodies.
• Aggregation behavior is pH-dependent, particularly near the iso-electric point.
• Steric/brush effects likely contribute significantly to suspension stability and aggregation, beyond classical forces.