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Phases of bacterial growth in batch culture

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Phases of microbial growth that are observed under Batch Culture
condition:-
In batch culture, biomass can be added in the fermenter or bioreactor only once. It is the most
common type of culture method used due to its simplicity and low cost. This type of system
is called closed system in which the volume of biomass and substrate is limited as there is no
input or output of material once the fermentation process starts. The resources are finite and
culture environment changes continuously as the fermentation proceeds leading to different
phases of growth of the microbes present as biomass. These phases includes:-
1. Lag phase
2. Acceleration phase
3. Log phase
4. Deceleration phase
5. Stationary phase
6. Death phase
The nutrients added as substrates are used by the growing cells and one of them is exhausted
after some time (one is exhausted faster than other nutrients), it is known as limiting
substrate. Thus the further growth is slowed down and microbes show different phases of
growth.
1. Lag phase- When microorganisms are added into fresh culture medium, the number of
cells do not divide immediately because of several reasons like the cells are synthesising new
components for their growth since the cells may be old and are deficient in ATP, essential
cofactors and ribosomes which must be synthesised before the growth begins, it takes time to

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adapt into new environment as the nutrients and pH may vary from that of their previous
environment and therefore new enzymes may be required by the microbes to utilize these
nutrients, in case the microorganisms are injured while transferring from one medium to
another they require some healing time to recover. Length of lag phase is variable based on
the new physiological conditions and the phase microorganisms were in when inoculated (for
example, lag phase does not occur if the inoculated culture is in exponential/log phase).
2. Acceleration phase- It is a very short and transient phase that cause the cells to initiate
their growth. In other words, it is just a phase that connects lag and log phase.
3. Log/Exponential phase- This is the phase where microorganisms most actively shows
growth and multiplication however, the rate of growth remains constant during this phase.
Exponential growth is said to be balanced growth where all the constituents are manufactured
and utilized at constant rate with respect to each other until the limiting substrate condition
occurs.
4. Deceleration phase- When microorganisms slowly begin to cease their growth, a short
lived phase occurs before all the cells finally stops growing. This phase may not be
observable every time.
5. Stationary phase- Now the substrates are depleted completely in the growth medium
which cause the cells to cease their growth forming a horizontal line in the growth curve.
After fermentation, a particular end product is formed which may inhibit the further growth
of microorganisms after certain level which is known as feedback inhibition. Now there is no
more multiplication of cells therefore the cell count stays constant but they are metabolically
active.

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1 Phases of microbial growth that are observed under Batch Culture condition:In batch culture, biomass can be added in the fermenter or bioreactor only once. It is the most common type of culture method used due to its simplicity and low cost. This type of system is called closed system in which the volume of biomass and substrate is limited as there is no input or output of material once the fermentation process starts. The resources are finite and culture environment changes continuously as the fermentation proceeds leading to different phases of growth of the microbes present as biomass. These phases includes:1. Lag phase 2. Acceleration phase 3. Log phase 4. Deceleration phase 5. Stationary phase 6. Death phase The nutrients added as substrates are used by the growing cells and one of them is exhausted after some time (one is exhausted faster than other nutrients), it is known as li ...
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