Power consumption and maximum energy dissipation in a milliliter-scale bioreactor

Area of Science:

• Biochemical Engineering
• Fluid Dynamics
• Process Scale-up

Background:

• Scaling up bioprocesses requires understanding power consumption and energy dissipation in bioreactors.
• Milliliter-scale bioreactors offer advantages for high-throughput screening but require careful scale-up considerations.

Purpose of the Study:

• To compare power characteristics and local energy dissipation between milliliter-scale and laboratory-scale stirred tank bioreactors.
• To investigate the impact of impeller design and scale on energy distribution within bioreactors.
• To provide data for reliable scale-up of bioprocesses.

Main Methods:

• Measured power consumption and maximum local energy dissipation in 12 mL and 1,200 mL stirred tank bioreactors.
• Utilized a gas-inducing impeller in the milliliter-scale reactor and Rushton turbines in the laboratory-scale reactor.
• Employed a clay/polymer flocculation system to quantify maximum local energy dissipation.

Main Results:

• Identical power characteristics (Newton number vs. Reynolds number) were observed across scales.
• The transition from laminar to turbulent flow occurred at a Reynolds number of 3,000 in the milliliter-scale reactor.
• Milliliter-scale bioreactors exhibited more uniform power distribution (epsilon(max)/epsilon(ø) ≈ 10) compared to laboratory-scale reactors (epsilon(max)/epsilon(ø) ≈ 16).

Conclusions:

• Milliliter-scale bioreactors with gas-inducing impellers provide more homogeneous energy dissipation.
• The findings support the principle that a higher impeller diameter to reactor diameter ratio leads to more uniform power distribution.
• Adjusting impeller speeds based on these findings facilitates robust scale-up of bioprocesses from milliliter to liter scales.