Effect of High-Speed Shaking on Oxygen Transfer in Shake Flasks

Area of Science:

• Biotechnology and Bioprocess Engineering
• Microbial Cultivation and Fermentation Technology

Background:

• Shake flasks are standard for early-stage bioprocess development but have limited oxygen transfer capacity.
• Increasing shaking frequency is key to enhancing oxygen supply in orbital shakers.
• Oxygen-demanding processes are challenging to perform effectively in conventional shake flasks.

Purpose of the Study:

• To evaluate the performance of a novel self-balancing orbital shaker for enhanced oxygen transfer.
• To determine the maximum oxygen transfer capacity (OTRmax) and mass transfer coefficient (kLa) at high shaking frequencies.
• To assess the impact of shaking diameter on oxygen supply and system stability.

Main Methods:

• Utilized a prototype self-balancing orbital shaker capable of high-speed operation (up to 750 rpm at 25 mm diameter).
• Conducted Kluyveromyces lactis cultivations in a 250 mL glass shake flask with hydrophilic properties.
• Employed a modified TOM system to monitor OTRmax and calculate kLa values.
• Investigated varying filling volumes (10 mL) and shaking diameters (25 mm and 50 mm).

Main Results:

• Achieved a maximum kLa value of 650 h⁻¹ (OTRmax = 135 mmol/L/h) at 10 mL filling volume and 25 mm shaking diameter.
• Demonstrated a ~50% increase in oxygen transfer capacity compared to existing commercial orbital shakers.
• Identified 25 mm shaking diameter as optimal for high-speed shaking, minimizing centrifugal force impact.

Conclusions:

• The self-balancing orbital shaker significantly improves oxygen supply in shake flasks, exceeding current technologies.
• High-speed shaking, particularly at a 25 mm diameter, offers new possibilities for microbial screening and bioprocess development.
• This technology facilitates more efficient cultivation of oxygen-sensitive microorganisms in early-stage development.