Microbubble assisted polyhydroxybutyrate production in Escherichia coli.

Area of Science:

• Biotechnology
• Microbiology
• Chemical Engineering

Background:

• Aerobic fermentation of Escherichia coli requires adequate dissolved oxygen, which becomes limiting at high cell densities.
• Poor oxygen solubility in aqueous media hinders optimal cell growth and bioproduct formation in large-scale cultures.
• Microbubble dispersion (MBD) technology offers a potential solution by increasing the surface area for oxygen transfer.

Purpose of the Study:

• To evaluate the efficacy of MBD technology in enhancing aerobic fermentation of a recombinant E. coli strain.
• To compare polyhydroxybutyrate (PHB) production yields under conventional versus MBD aerobic fermentation conditions.

Main Methods:

• Utilized a recombinant E. coli strain for polyhydroxybutyrate (PHB) production.
• Conducted aerobic fermentation experiments under both conventional sparging and MBD conditions.
• Maintained consistent bioreactor parameters (350 rpm, 0.8 vvm air flow rate) for comparative analysis.

Main Results:

• Conventional fermentation achieved an optical density at 600 nm (OD600) of 6.21 and a PHB yield of 23% (dry cell basis).
• MBD fermentation resulted in a significantly higher OD600 of 8.17 and a PHB yield of 43% (dry cell basis).
• MBD fermentation nearly doubled the PHB yield compared to conventional methods.

Conclusions:

• MBD technology effectively enhances oxygen mass transfer into the fermentation medium.
• The improved oxygen availability via MBD leads to increased E. coli growth and bioproduct (PHB) generation.
• MBD represents a promising advancement for optimizing large-scale aerobic fermentation processes.