Scale-up of a cyclone bioreactor

Area of Science:

• Biotechnology
• Biochemical Engineering
• Microbial Production

Background:

• Cyclone bioreactors utilize pumped recirculation for agitation, differing from stirred tanks.
• Oxygen transfer in cyclone bioreactors occurs at the gas-liquid interface or via entrained bubbles.
• Scaling up bioreactors presents challenges in maintaining optimal operating conditions.

Purpose of the Study:

• To scale up a cyclone bioreactor from a 1 dm3 to a 75 dm3 Process Development Unit (PDU).
• To compare the performance of the scaled-up and laboratory-scale cyclone bioreactors for poly-beta-hydroxybutyrate (PHB) production.
• To evaluate the impact of operating conditions on oxygen transfer and PHB accumulation.

Main Methods:

• Scale-up of a cyclone bioreactor, adjusting aspect ratio and recirculation loop.
• Aeration strategy optimization in the 75 dm3 PDU.
• Cultivation of Alcaligenes eutrophus DSM 545 for PHB production under nitrogen-limited conditions.
• Comparison of dissolved oxygen levels and PHB accumulation between reactor scales.

Main Results:

• The scaled-up PDU achieved comparable oxygen transfer capability to the laboratory-scale reactor with balanced aeration and similar power input (17 J s-1 dm-3).
• Dissolved oxygen levels in the PDU were sensitive to air injection points.
• Alcaligenes eutrophus consistently achieved over 80% PHB accumulation of biomass dry weight.
• A lower yield of PHB on glucose was observed in the PDU compared to the laboratory-scale reactor.

Conclusions:

• The cyclone bioreactor can be successfully scaled up for microbial PHB production.
• Optimized aeration and power input are crucial for maintaining oxygen transfer in larger cyclone bioreactors.
• While PHB accumulation is high, process optimization is needed to improve glucose yield in scaled-up systems.