A simple substrate feeding strategy using a pH control trigger in fed-batch fermentation.

Area of Science:

• Biotechnology
• Microbial Fermentation
• Process Control

Background:

• High-cell-density fed-batch fermentation is crucial for producing biomass and metabolites.
• Accurate control of nutrient feeding, especially glucose, is essential for optimizing fermentation processes.
• Traditional methods often rely on direct glucose measurement, which can be complex and costly.

Purpose of the Study:

• To develop a simple, automated glucose feeding strategy for fed-batch fermentation using pH control.
• To demonstrate the effectiveness of this strategy for biomass production in Escherichia coli.
• To evaluate the performance of the strategy with different pH controllers.

Main Methods:

• Developed an automated glucose feeding strategy based on pH control, using acidified glucose solution.
• Determined glucose addition frequency based on culture growth kinetics.
• Conducted fed-batch fermentations with indigenous and recombinant Escherichia coli strains.
• Compared a portable pH controller with a proportional-integral-derivative (PID) controller.

Main Results:

• Achieved high biomass production (optical density > 40 at 600 nm) for both E. coli strains.
• Successfully applied the pH-controlled glucose feeding strategy with both types of pH controllers.
• Observed improved control performance with the more sophisticated PID controller.
• Demonstrated effective indirect glucose control without online glucose measurement.

Conclusions:

• A simple pH-based glucose feeding strategy can effectively achieve high-cell-density fed-batch fermentation.
• This method is adaptable to conventional bioreactors and simplifies the process by eliminating the need for online glucose sensors.
• The strategy shows promise for optimizing biomass and secondary metabolite production.