Oxygen transfer in slurry bioreactors.

Area of Science:

• Biochemical Engineering
• Fluid Dynamics
• Mass Transfer

Background:

• Oxygen transfer is critical for bioreactor efficiency.
• Slurries with yield stress exhibit complex rheological properties affecting mass transfer.
• Existing models may not adequately capture oxygen transfer in non-Newtonian fermentation broths.

Purpose of the Study:

• To investigate oxygen transfer in bioreactors with yield-stress slurries.
• To develop and validate a theoretical correlation for volumetric mass transfer coefficients.
• To assess the correlation's applicability to simulated and actual fermentation broths.

Main Methods:

• Experiments were conducted in a 40-L bubble column bioreactor.
• Rheological properties of simulated broths were modeled using the Casson model.
• Oxygen transfer data were compared against a theoretical correlation combining Higbie's penetration theory and Kolmogoroff's isotropic turbulence theory.

Main Results:

• The proposed theoretical correlation showed good agreement with experimental data for simulated fermentation broths.
• Re-examination of previous data for actual mycelial fermentation broths (correlated by Bingham plastic model) also fit the new correlation.
• The correlation effectively predicts oxygen transfer rates in non-Newtonian slurries.

Conclusions:

• A robust theoretical correlation for oxygen transfer in yield-stress slurries has been established.
• The developed model enhances the prediction of oxygen transfer in bioreactors, including those with mycelial broths.
• This work contributes to optimizing bioreactor design and operation for enhanced mass transfer.