A study of oxygen transfer in shake flasks using a non-invasive oxygen sensor

Area of Science:

• Biotechnology and Bioprocess Engineering
• Microbial Fermentation
• Oxygen Transfer Dynamics

Background:

• Shake flasks are widely used for microbial cultivation, but oxygen transfer limitations can impact fermentation outcomes.
• Understanding and quantifying oxygen transfer is crucial for reproducible bioprocess development and scale-up.
• Non-invasive optical sensors offer a reliable method for monitoring dissolved oxygen and characterizing mass transfer.

Purpose of the Study:

• To investigate the impact of shake flask parameters (plugs, baffles, media) on oxygen transfer.
• To measure the volumetric mass transfer coefficient (k(L)a) and plug resistances under various conditions.
• To compare oxygen transfer in shake flasks with stirred tank fermentors and assess implications for bioprocess scale-up.

Main Methods:

• Utilized a non-invasive optical sensor to monitor dissolved oxygen during Escherichia coli fermentation.
• Systematically varied shake flask configurations, including different plugs and the presence of baffles.
• Measured volumetric mass transfer coefficients (k(L)a) and analyzed plug resistances.
• Compared k(L)a values obtained in shake flasks with those from a bench-scale stirred tank fermentor.

Main Results:

• Dissolved oxygen profiles were significantly influenced by flask plugs, baffles, and media type.
• Volumetric mass transfer coefficients (k(L)a) were quantified across different experimental conditions.
• Similar growth and recombinant protein production kinetics were achieved in shake flasks and a stirred tank fermentor by matching k(L)a values.
• Quantitative data provided a direct comparison of oxygen transfer efficiencies between shake flask and fermentor systems.

Conclusions:

• Shake flask oxygen transfer can be effectively characterized and manipulated by optimizing parameters like plugs and baffles.
• Matching k(L)a between shake flasks and fermentors enables comparable bioprocess performance, facilitating reliable scale-up.
• This study offers valuable insights for optimizing shake flask cultivations and bridging the gap to larger-scale fermentation.