This document discusses three main modes of fermentation: batch culture fermentation, continuous culture fermentation, and fed batch culture fermentation. Batch culture fermentation involves a closed system with limited initial nutrients that microbes pass through lag, log, stationary, deceleration, and death phases. Continuous fermentation maintains exponential growth by continuously adding fresh medium and removing culture. Fed batch culture adds medium without removing culture, initially operating in batch mode before strategies like continuously adding limiting substrates are used to increase biomass concentration while maintaining a constant cell concentration and decreasing growth rate in quasi steady state.

1. MODES OF
FERMENTATION
Submitted by :
Udisha Sharma
b.Sc (pc) v sem 22440
Submitted to:
Dr. Neha Batra

2. Types :
1.Batch culture fermentation
2.Continuous culture fermentation
3.Fed batch culture fermentation
Fermenter

3. Batch fermentation
• Batch fermentation is a discontinuous process and the fermenter has to
be cleaned after each process and a fresh batch started.
• It is a closed culture system which contain an initial limited amount of
nutrient.The inoculated culture will pass through a no. of phases as
shown:

4. 1. Lag phase: initial phase, no apparent growth of microbes ,they adapt to the
environmental conditions, but an inc. in mass.
2. Log phase: microbial growth proceeds at the maximum possible rate. Also
known as exponential phase.
3. Stationary phase: no overall growth rate i.e death of the cells is equal to
the division of cells. Most of the secondary metabolites are produced in this
phase.
4. Deceleration phase: decline in the growth rate of microbes.
5. Death rate : no growth at all, cell starts to die and the population size
decreases. Usually the fermentation stops before the death phase.

7. Continuous Fermentation
• It is a continuous process where nutrient is continuously added to the
fermenter at a fixed rate.
• Exponential growth in the batch culture may be prolonged by addition of
fresh medium to the vessel, provided that the medium is designed such that
the growth is substrate limited and not toxin limited ,exponential growth
will proceed until the additional substrate is exhausted.
• The organism are continuously maintained at logarithm stage.
• If an overflow device was fitted to the fermenter such that the added
medium placed at equal volume of culture from the vessel then continuous
production of cells could be achieved.
• The products are recovered continuously.
• The fermenter in this type are called “flow through fermenters”.

10. Fed Batch culture
• Yoshida et al in 1973 introduced the term fed batch culture to describe
batch cultures which are fed continuously or sequentially with medium
without the removal of culture fluid.
• A fed batch culture is established initially in the batch mode and is then
according to one of the strategies-
1. The same medium which is used to established batch culture is added
resulting in the inc. in volume.
2. A solution of limiting substrate at the same conc. as that in the initial
medium is added resulting in the inc. in the volume.
3. A conc. solution of the limiting substrate is added at the rate less than (1)
& (2) resulting in inc. in volume.
4. A very conc. solution of limiting substrate is added at a rate less than
(1),(2) &(3) resulting in insignificant inc. in volume.

11. The biomass conc. at the stationary phase in a batch culture can be described
as-

13. Thus from above equation it may be concluded that input of substrate is
compensated by substrate consumption. Thus ds/dt =0
Total biomass (X) concentration increases with time but cell concentration (x)
remains constant, i.e. dx/dt = 0 and we can now write
μ= D
This situation is quasi steady state.
The difference between steady state in chemostat and quasi steady state in fed
batch is that μ is constant in chemostat and it decreases in fed batch.