2. •Fermentation is a metabolic process that
converts sugar to acids, gases or alcohol.
• It occurs in yeast and bacteria, and also in
oxygen-starved ( Deficient ) muscle cells, as
in the case of lactic acid fermentation.
• Fermentation, chemical process by which
molecules such as glucose are broken down
anaerobically.
Fermentation:
4. •Batch culture technique is also called as closed system
of cultivation.
•In this technique at first nutrient solution is prepared
and it is inoculated with inoculum and then nothing is
added in the fermentation tank except aeration.
•In batch culture, neither fresh medium is added nor
used up media is removed from the cultivation vessel.
Therefore volume of culture remains same.
•Since fresh media is not added during the course of
incubation, concentration of nutrition decreases
continuously. Furthermore various toxic metabolites
also accumulates in the culture vessel. Therefore batch
culture technique gives characteristics growth curve
with lag phase, log phase, stationary phase and decline
phase.
5.
6. Lag phase: microbial population remains constant as
there is no growth .However it is the period of
intense metabolic activity.
Exponential phase: cells divide with increasing
frequency till it reaches the maximum growth rate.
At this point logarithmic growth begins and cell
numbers and cell biomass increase at constant
rate.
7. Stationary Phase
The specific growth rate of the microorganism
continues decelerating until the substrate is
completely depleted.
Overall growth rate has declined to zero and
there is no net change in cell numbers/ biomass
i.e. rate of cell division equals rate of cell death.
Microorganisms are still metabolically active,
metabolizing intracellular storage compounds,
utilizing nutrients released from lysed cells and in
certain cases produce secondary metabolites.
Death rate: cells die at constant rate and
undergone lysis.
8. •Continuous culture technique is also called as open
system of cultivation.
•In this technique fresh sterile medium is added
continuously in the vessel and used up media with
bacterial culture is removed continuously at the same
rate. So the volume and bacterial density remain same
in the cultivation vessel.
•In this technique, bacteria grow continuously in their
log phase. This type of growth is known as steady state
growth.
•The cell density in continuous culture remains
constant and it is achieved by maintaining constant
dilution and flow rate.
11. •Fed-batch culture is also called as semi-closed system of
cultivation.
•In this technique, at first nutrient media is prepared and
it is inoculated with culture organism and then incubated
for particulate time.
•During the course of incubation a particular nutrient is
added at intervals without removing the used up media
so the volume of culture increases continuously.
•Fed batch culture technique is applied in many types of
fermentation process.
•In fermentation some nutrient is very essential for the
process but when these nutrients are provided in higher
concentration in the culture they inhibit the growth of
bacteria ultimately ceasing the fermentation.
•Therefore such nutrients are kept in lower
concentration initially and it is added slowly and
continuously during the course of fermentation.
12. Difference b/w batch,continuous
and fed batch:
Characteristics Batch culture Fed-batch culture Continuous culture
Cultivation system Closed type Semi-closed type Open type
Addition of fresh nutrition No Yes Yes
Volume of culture Constant Increases Constant
Removal of wastes No No Yes
Chance of contamination minimum Intermediate Maximum
Growth phase
Lag, log, stationary and
decline phase
Lag, log , stationary and
decline phase
Lag and log phase
Log phase Shorter longer Longest and Continuous
Density of bacteria Change with time Change with time Remain same
Product yield Low Medium High
