About microbial growth kinetics

1. SRI PARAMAKALYANI COLLEGE
REACCREDITED WITH A+ GRADE WITH A CGPA OF 3.39 IN THE THIRD CYCLE OF NAAC
AFFILIATED TO MANOMANIUM SUNDARANAR UNIVERSITY, TIRUNELVELI.
ALWARKURICHI 627 412, TAMIL NADU, INDIA
POST GRADUATE & RESEARCH
DEPARTMENT OF MICROBIOLOGY
(Government Aided)
ACADEMIC YEAR 2022-2023
IV SEM CORE: INDUSTRIAL MICROBIOLOGY
UNIT- 2
MICROBIAL GROWTH KINETICS
Submitted to,
Dr. S.VISWANATHAN Ph.D.
Assistant Professor and Head,
Department of Microbiology.
Sri Paramakalyani College.
Submitted by,
A.MANI BHARATHI
Reg. No:20211232516113
II M.Sc. Microbiology.
Assigned on:
Submitted on:

2. We should understand about growth kinetics of
the micro organisms for the large scale process
and fermentation.

3. Microbial fermentation in liquid media can be
carried out under different operating conditions.
 Batch Growth
 Fed-Batch Growth
 Continuous Growth

4. Batch Growth
Batch growth involves a closed system where all
nutrients are present at the start of the
fermentation within a fixed volume.

6. Fed-Batch Growth
In fed-batch systems, fresh medium are fed
continuously, intermittently or are added as a
single supplement and the volume of the batch
increases with time.

7. Continuous growth
Continuous systems are open systems where
fresh medium is continuously fed into the
fermentation vessel, but the volume remains
constant as spent medium and cells are removed
at the same rate.

9. Microbial Growth Kinetics
❏Lag Phase
❏Log Phase
❏Stationary Phase
❏Death Phase

10. Lag Phase
 In this phase, The Cells are transferred into the sterilized
medium.
 The cells are adapting themselves into the new sterile medium
and new environment.
 Several Parameters such as change in pH Value, increase in
supply of nutrients, decrease of growth inhibitors.
 The cells doesn’t replicate in this phase but they grow in this
phase and there is a change in mass of the cells.

11. Log Phase
● By the end of the lag phase, the cells have adapted to the new
conditions of growth.
● The cells present in the medium starts to proliferate in unit time
respective to the nature of the organism, substrate concentration
and conditions in the medium.
● It is calculated quantitatively as doubling of number of the cells
or the doubling of the biomass concentration per unit time.

12.  There is a Semilogarithmic graph, a straight line occurs.
 The cells alter the medium through uptake of substrates and
excretion of metabolic products, the growth rate remain constant
in this phase.
 Growth rate is independent of substrate concentration as long
as excess substrate is present.

13. Generation time is referred to the time taken for the cell to divide
and it is also known as Doubling time.

14. There are two types of condition in growth:
● Asynchronus Growth
● Synchronus Growth
Asynchronous Growth is the condition in which the cells or
biomass present in the medium may be different phases of cell
growth.
Synchronous Growth is the condition in which the cells present
are in the same phase of cell growth.

15. The rate of increase in biomass is correlated with the
❏ Specific growth rate (μ)
❏ Biomass concentration (X)
dX∕dt=μ.X
The rate of increase in number of cells is correlated with
❏ Specific growth rate (μ)
❏ Cell Density (N)
dN∕dt=μ.N

16. The impact of essential nutrient depletion on
growth can be described ,mathematically by the
Monod equation as follows:

17. The specific growth rate (μ), is generally found to be a function
of three parameters; the concentration of limiting substrate, S, the
maximum growth rate (μmax) and a substrate specific constant Ks.
μ= μmax.S
( Ks + S)

18.  The constant Ks is the substrate concentration at which half
the maximum specific growth rate is obtained.
 Ks is equivalent to the Michaelis - Menton constant in
enzyme kinetics.
 It is known as the half-velocity constant.

19. Diauxy condition
 When complex nutrient solutions are used, two log phases
frequently occur separated by a second log phase.
 This arises because one of the substrates is catabolized
preferentially.
 The presence of this one substrate represses the break down of
the other substrates.
 The catabolic enzymes for the other substrates are induced
only after the first substrate has been completely metabolized.

20. Stationary Phase
 The specific growth rate of the microorganism continues
decelerating until all of the available limiting substrate is
metabolized.
 Growth is no longer sustainable and the growth is zero.
 The rate of cell division equals to the rate of cell death.

21.  There will be a horizontal straight line as the growth rate is
comparatively similar to the death of the cells.
 Due to lysis, new substrates are released, which then may
serve as energy sources for the slow growth of the survivors.
 It is due to the presence of primary, secondary metabolites and
the nutrients.

22. Death Phase
 In this phase the energy reserves of the cells are exhausted.
 A straight line may be obtained when a semi-logarithmic plot is
made of survivors vs time, indicating that the cells are dying at an
exponential rate.
 The length of time between the stationary phase and the death
phase is dependent on the organism and the process used.

23. REFERENCE
● Textbook on Industrial Microbiology by L. E Casida
● A Textbook of Industrial Microbiology by Wulf Crueger and
Anneliese Crueger.
● Industrial microbiology - Michael.J.Waites, Neil.L.Morgan,
John.S.Rockey, Gary Higton

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26. THANKS TO
THE CHAIRMAN.
THE SECRETARY.
MANAGEMENT COMMITTEE.
THE PRINCIPLE, SRI PARAMAKALYANI COLLEGE.
THE HEAD, DEPARTMENT OF MICROBIOLOGY.
THE STAFF MEMBERS, DEPARTMENT OF MICROBIOLOGY.