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The Use of Chemostats in Microbial Systems Biology
13:19

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Published on: October 14, 2013

The pH-auxostat as a tool for studying microbial dynamics in continuous fermentation.

G Larsson1, S O Enfors, H Pham

  • 1Department of Biochemistry and Biotechnology, The Royal Institute of Technology, S-100 44 Stockholm, Sweden.

Biotechnology and Bioengineering
|July 1, 1990
PubMed
Summary

The pH-auxostat method controls continuous fermentation by separating nutrient and acid/alkali flows. This allows for controlled, high cell mass concentrations and detection of growth rate deviations.

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Area of Science:

  • Biotechnology
  • Microbial Physiology
  • Fermentation Technology

Background:

  • Microbial growth often involves acid or alkali production/consumption.
  • Controlling pH is crucial for optimizing fermentation processes.
  • Existing methods may limit cell mass concentration or risk washout.

Purpose of the Study:

  • To introduce and validate the pH-auxostat for controlling continuous fermentation.
  • To demonstrate its capability in achieving high cell mass concentrations without washout.
  • To utilize it for investigating microbial physiological responses to environmental changes.

Main Methods:

  • Implementing a pH-auxostat by splitting inlet substrate flow into nutrient and concentrated acid/alkali streams.
  • Developing a modified expression for steady-state biomass concentration based on hydrogen ions.
  • Conducting experiments with Escherichia coli to assess the impact of temperature and ammonia concentration on growth rate.

Main Results:

  • The pH-auxostat enables control over cell mass concentration, allowing maximal growth rates.
  • A proportional relationship was established between pH difference and steady-state cell mass concentration.
  • The method successfully detected physiological deviations from maximal growth rates under varied conditions.

Conclusions:

  • The pH-auxostat is an effective tool for controlling continuous fermentation and achieving high cell densities.
  • It provides a means to study microbial responses to environmental factors like temperature and ammonia.
  • This technique enhances the understanding and optimization of microbial cultivation.