Parallel substrate supply and pH stabilization for optimal screening of E. coli with the membrane-based fed-batch...

Area of Science:

• Biotechnology
• Microbial Cultivation
• Bioprocess Engineering

Background:

• Fed-batch operation is crucial for microbial cultivations facing challenges like oxygen limitation and substrate inhibition.
• The membrane-based fed-batch shake flask was developed for screening but lacked nutrient replenishment and pH stabilization.
• Previous methods required high buffer concentrations, leading to suboptimal osmolality for Escherichia coli.

Purpose of the Study:

• To establish a simultaneous multi-component release of glucose and an alkaline compound from a reservoir.
• To enable Escherichia coli cultivations within its optimal physiological range using a membrane-based fed-batch shake flask.
• To overcome limitations of nutrient depletion and pH fluctuations in shake flask cultures.

Main Methods:

• Development of a membrane-based fed-batch shake flask with a multi-component release system.
• Simultaneous release of glucose and ammonium carbonate from the reservoir.
• Monitoring of respiratory activity and biomass concentration.
• Comparison with traditional batch cultivation methods.

Main Results:

• The system enabled detection of ammonium limitation and stabilized pH through ammonium carbonate release.
• Achieved biomass concentration up to 25 g/L, a high value for shake flask cultivation in defined media.
• Reduced buffer concentration by 75%, establishing optimal osmolality for cultivation.
• Multi-component fed-batch cultivation resulted in a twofold higher biomass concentration compared to batch cultivation.

Conclusions:

• The multi-component release system replenishes substrates, stabilizes pH, and maintains optimal osmolality.
• This approach significantly enhances biomass and product concentrations compared to batch cultivations.
• The optimized membrane-based fed-batch shake flask is a powerful tool for microbial screening and bioprocess development.