CONTINIOUS CULTURE OF MICROORGANISMS
- A Continuous culture is an Open system.
- The concept of the Continuous cultures dates from the 19th Century when a continuous process for the conversion of waste Beers and Wines to Vinegar was developed.
- Continuous culture systems can be operated as (i) Chemostat or (ii) Turbidostat.
- The Turbidostat operates best at high dilution rates; the Chemostat is most stable and effective at low dilution rates.
- The most common Continuous culture is Chemostat.
(i) Chemostat
- A Chemostat (from chemical environment is static) is a Bioreactor to which fresh medium is continuously added, while culture liquid containing left over nutrients, metabolic end products and microorganisms are continuously removed at the same rate to keep the culture volume constant.
- In Chemostat, both Growth
rate and Cell density can be controlled independently.
ü
Growth rate -
How fast the cells divide.
ü
Cell density -
How many cells per ml are obtained.
- Two factors govern Growth
rate and Cell density, respectively:
1)
The Dilution rate,
which is the rate at which fresh medium is pumped in and spent medium is
removed.
2)
The Concentration of
a limiting nutrient, such as a carbon or nitrogen source, present in
the sterile medium entering the Chemostat vessel.
Applications of Chemostat
- A practical advantage to the Chemostat is that a cell population can be maintained in the Exponential growth phase for long periods, days or even weeks. Exponential phase cells are usually most desirable for physiological experiments, and such cells can be available at any time when grown in a Chemostat.
- The Chemostat has been used in Cell Biology, Microbial Physiology and Microbial Ecology (Microbial Interaction).
- Chemostat have also been used for Enrichment and isolation of bacteria which are resistant to Antibiotics and Bacteriophages from nature.
- Chemostats are frequently used in the industrial manufacturing of Ethanol, Amino acids and Organic acids.
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