Difference Between Chemostat and Turbidostat

The key difference between chemostat and turbidostat is that a single nutrient can limit the microbial growth inside the chemostat while a single nutrient cannot control the microbial growth inside the turbidostat.

Microorganisms are grown in liquid cultures in order to multiply them in a large scale. Continuous microbial culture technique is one type of industrial fermentation technique in which microbial growth is maintained at an exponential phase. Chemostat and turbidostat are two major types of continuous culture systems.

CONTENTS

1. Overview and Key Difference
2. What is Chemostat 
3. What is Turbidostat
4. Similarities Between Chemostat and Turbidostat
5. Side by Side Comparison – Chemostat vs Turbidostat in Tabular Form
6. Summary

What is Chemostat?

Chemostat is a type of continuous culture system in which a single nutrient/component of the medium controls the growth rate of the microbes. It is an open culture system and has a continuous feed of fresh nutrients at a constant rate. Continuous removal of culture at a constant rate from the other side keeps the volume inside constant. The name ‘Chemostat’ implies that the growth rate of the chemostat can be controlled by a single component of the culture medium inside the fermenter.

Figure 01: Chemostat

However, the continuous feed of culture medium fulfills the optimum nutritional requirement. Dilution rate or the rate of adding nutrient always determines the growth rate of the microbes inside the chemostat.

What is Turbidostat?

Turbidostat is another type of continuous culture system in which internal culture reactions control the specific growth rate. Culture biomass maintains at a constant by measuring the optical density of the culture medium using a photometer. When turbidity comes to a certain level, medium pump switches on and adjusts the turbidity to the required level. Internal culture volume is also at a constant in this system. Furthermore, the growth rate of the microbes does not depend on a single component of the culture medium. Neither does the flow rate remains constant.

What are the Similarities Between Chemostat and Turbidostat?

• Chemostat and turbidostat are continuous culture systems.
• Both of them are open culture systems.
• In both systems, culture volume is constant.
• The environmental conditions are constant in both systems.
• In both systems, culture duration is indefinite.

What is the Difference Between Chemostat and Turbidostat?

Summary – Chemostat vs Turbidostat

Chemostat and turbidostat are two continuous culture systems. Chemostat has a constant flow rate and a single component of the culture medium can control the growth rate of the microbes in it. Turbidostat does not have a constant flow rate. Flow rate varies based on the culture biomass. The optical density of the culture biomass can be measured by a photometer and adjusted into a constant by switching on and off the medium pump. This is the difference between chemostat and turbidostat.

Reference:

1. Moore, David, et al. “21st Century Guidebook to Fungi by David Moore, Geoffrey D. Robson and Anthony P. J. Trinci.” The Effects of Mycorrhizas, 1 Dec. 2008, Available here.
2. “Turbidostat.” Egyptian Journal of Medical Human Genetics, Elsevier, Available here.

Image Courtesy:

1. “Chemostat Vessel Diagram” By CGraham2332 – Own work (CC BY-SA 4.0) via Commons Wikimedia

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