Mass Transfer and Rheological Characteristics in a Stirred Tank Bioreactor for Cultivation of Escherichia coli BL21

Sohail Rasool Lone, Vimal Kumar, Jeffrey R. Seay, Derek L. Englert, Hyun Tae Hwang

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


With the rapid growth of pharmaceutical and biotechnology industry, stirred tank bioreactors have received much attention due to simple design, easy control of operating conditions, and low operating cost. In the development of commercial processes, however, a transition from laboratory to industrial scale faces great challenges because many properties related to size change nonlinearly as a system increases. In this context, along with an understanding of fluid dynamics, application of an efficient method for scale-up is critical for designing successful industrial process. Particularly in cell cultivation processes, it is important to evaluate the oxygen transfer and viscous properties of liquid medium. In the present study, the effect of various key operating variables such as agitation rate and aeration rate, impeller diameter, and bioreactor working volume for different impellers on the volumetric mass transfer coefficient (kLa) have been investigated in a stirred tank bioreactor for cultivating Escherichia coli BL21. It was found that the kLa tends to increase with the operating variables except the bioreactor working volume. Among the tested impellers, the pitched blade was observed to be most promising because of relatively higher kLa but less shear force owing to its low power number. It was also found that the liquid medium with E. coli behaves as a Newtonian liquid. Compared to conventional designs of Rushton turbines, dislocated Rushton turbine was found to deliver higher kLa. Finally, using dimensional analysis, the kLa for different impeller configurations was correlated in the form of dimensionless groups, suggesting that this approach can be used for predicting kLa in different scales of stirred tank bioreactors.

Original languageEnglish
Pages (from-to)766-776
Number of pages11
JournalBiotechnology and Bioprocess Engineering
Issue number5
StatePublished - Sep 1 2020

Bibliographical note

Funding Information:
This work was jointly supported by the collaborative research program of the University of Kentucky and the Indian Institute of Technology Roorkee. The financial assistance by the Ministry of Human Resource Development (MHRD), Government of India is also gratefully acknowledged. The authors declare no conflict of interest. Neither ethical approval nor informed consent was required for this study.

Publisher Copyright:
© 2020, The Korean Society for Biotechnology and Bioengineering and Springer.


  • Escherichia coli
  • dimensional analysis
  • gas-liquid system
  • mass transfer coefficient
  • stirred tank bioreactor

ASJC Scopus subject areas

  • Biotechnology
  • Bioengineering
  • Applied Microbiology and Biotechnology
  • Biomedical Engineering


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