Microbial high cell density fermentations in a stirred single-use bioreactor

Area of Science:

• Biotechnology and biopharmaceutical manufacturing.
• Microbial fermentation processes.

Background:

• Single-use bioreactors are increasingly adopted in the biopharmaceutical industry due to cost and operational advantages.
• However, their application in microbial fermentations is limited by lower oxygen transfer and cooling capacities.
• This study investigates the suitability of a stirred single-use bioreactor for microbial applications.

Purpose of the Study:

• To evaluate the microbial suitability of a stirred single-use bioreactor.
• To determine key process engineering parameters: volumetric mass transfer coefficient (kLa), mixing time, and heat transfer coefficient.
• To develop a control space for microbial fermentation based on these parameters.

Main Methods:

• Characterization of volumetric mass transfer coefficient (kLa), mixing time, and heat transfer coefficient in a stirred single-use bioreactor.
• Development of a mathematical model based on kLa characteristics.
• High cell density fermentations of Escherichia coli and Pichia pastoris were performed to verify the control space.

Main Results:

• High cell densities were achieved: OD600 = 175 (60.8 g/L dry cell weight) for E. coli and 381 g/L wet cell weight for P. pastoris.
• These cell densities are comparable to those obtained in stainless steel bioreactors.
• Recombinant protein expression titers reached up to 9 g/L, demonstrating successful production.

Conclusions:

• Stirred single-use bioreactors are a viable option for high cell density microbial fermentations.
• The characterized parameters and developed control space enable efficient microbial cultivation in single-use systems.
• This technology offers a promising alternative for biopharmaceutical production, leveraging the benefits of single-use systems.