Phases of Cell Growth and Biomass Doubling Time
Explore the four phases of cell growth - Lag, Exponential, Stationary, and Death phases, along with the concept of biomass doubling time. Discover the factors influencing bacterial growth in various bioreactor environments. Get insights into specific growth rates and their role during the growth cycle.
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Presentation Transcript
Phases of cell growth Cell growth can be modelled with four different phases: Lag phase: Cells adapt themselves to growth conditions. It is the period where the individual bacteria are maturing and not yet able to divide. Exponential phase (log phase) is a period characterized by cell doubling.The number of new bacteria appearing per unit time is proportional to the present population.
Stationary phase is often due to a growth-limiting factor such as the depletion of an essential nutrient, and/or the formation of an inhibitory product such as an organic acid. Stationary phase results from a situation in which growth rate and death rate are equal. At death phase, bacteria run out of nutrients and die.
If is constant w.r.t., then rearranging previous equation and integrating, we get: This equation applies only to the duration of the exponential growth phase, beyond which either substrate limitation or toxin accumulation become rate determining. or or
Doubling Time It is the time required to double the quantity of biomass, that is growing exponentially. X: X0 2X0 t: 0 td (The amount of biomass at the start must double) (Within a finite time, td, or doubling time) Substituting in 2X0 for X and td for t and logging both sides => , therefore Specific growth rate ( ) can be defined as any point during the growth cycle. During the exponential growth period is constant and at a maximum for that process under the specified conditions.
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