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Phases of bacterial growth in batch culture

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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