Numerical and experimental assessment of a miniature bioreactor equipped with a mechanical agitator and non‐invasive biosensors

Abstract

BACKGROUND: Sufficient oxygen supply and stable process control are crucial for the successful screening and process optimization of aerobic microorganisms in small-scale bioreactors. In this work, a miniature bioreactor (volume 80 mL) equipped with non-invasive biosensors was developed and characterized. RESULTS:To enable proper mixing and high oxygen transfer rate, a mechanical agitator with large diameter (0.56 tank diameter) and submerged aeration were applied. The flow fields formed in the miniature bioreactor under a wide range of conditions (filling volume 30-70 mL, agitation speed 300-1100 rpm and aeration rate 0-4 vvm) were numerically analyzed by computational fluid dynamics (CFD). The miniature bioreactor performed with a suitable mixing time (<4 s) and a high oxygen transfer coefficient (k L a > 1000 h −1 ). It showed that engineering parameters including mass transfer, mixing and shear were more sensitive to agitation than either filling volume or aeration. Correlations for quantitative evaluation of the engineering parameters were established. The predicted oxygen transfer coefficient by CFD showed good agreement with both experimental and reported data. Furthermore, cultivations of Escherichia coli and Pichia pastoris in the mini bioreactor verified the excellent performance.CONCLUSION: The developed miniature bioreactor will provide a reliable tool for screening and process optimization, and the presented correlations that predict the engineering parameters will make it convenient to achieve scale-up. GREEK LETTERSg air volume fraction (v/v) l water volume fraction (v/v) turbulence dissipation rate (m 2 s −3 ) l liquid density (kg m −3 ) surface tension force (N m −1 ) Kolmogorov length scale (m) l liquid kinematic viscosity (m 2 s −1 ) engineering parameter J Chem Technol Biotechnol 2019; 94: 2671-2683

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