Advantage

 

Comparison of Batch Culture and
Continuous Cultivation
 
 

In batch cultivation, the bacteria are inoculated into the
bioreactor (always stirred tank bioreactor). Then, under
certain conditions (temperature, pH, aeration, etc.) the
bacteria go through all the growth phases (lag,
exponential, stationary). At last, the fermentation is
stopped and  the product is collected. Then, after cleaning
and sterilization of the fermenter,  the fermenter is ready
for another batch.
In continuous cultivation, the fresh medium flows into the
fermentor continuously, and part of the medium in the
reactor is withdrawn from the fermenter at the same flow
rate of the inlet flow. The table below shows the
advantages and disadvantages of different modes of
operation of the stirred tank rector. (Ref 1.)
 

Mode of
operation

Advantages

Disadvantages

Versatile: can be
used for
different
reactions every
High labor cost: skilled
day.
labor is required
Safe: can be
Much idle time:
properly

Batch

sterilized.
         Little risk of
infection or
strain mutation
Complete
conversion of
substrate is
possible

Works all the
time: low labor
cost, good
utilization of
reactor
Often efficient:
due to the
autocatalytic
nature of
Continuous
microbial  
reactions, the
productivity can
be high.
Automation may
be very
appealing
Constant product
quality

Sterilization, growth of
inoculum, cleaning after the
fermentation
Safety problems: when
filling, emptying, cleaning

Often disappointing:
promised continuous
production for months fails
due to a. infection. b.
spontaneous mutation of
microorganisms to non
producing strain
Inflexible: can rarely be
used for other productions
without substantial
retrofitting

From the above comparison, although continuous culture
has some disadvantage, it can outperform batch culture by
eliminating the inherent down time for cleaning and
sterilization and the long lags before the organisms enter a
brief period of high productivity.

Continuous culture is superior to batch culture in several
ways for research. Interpretation of results is difficult for
batch culture because of changing concentrations of
products and reactants, varying pH and redox potential,
and a complicated mix of growing, dying, and dead cells.
Data from continuous cultures have much less complexity
because there are dynamic equilibria or small excursions
from steady state. Cause and effect relationships tend to be
obvious.
Reference:
1. "Bioreaction Engineering Principles", Jens Nielsen and John Villadsen
 
Last modify: 05/01/2000, by Xuezhen Kang