Introduction to Fermentation
FERMENTATIONFermenter is a vessel or tank in which whole cells
or cell-free enzymes transform raw materials into biochemical
products and/or less undesirable by-products. It is also termed as
Bioreactor.The basic function of a fermenter is to provide a
suitable environment in which an organism can efficiently produce a
target product that may be - cell biomass, - a metabolite, - or
bioconversion product.
Fermenter
INDUSTRIAL FERMENTERS Components of fermenter:Basic component
includes drive motor, heaters, pump, etc.Vessels and
accessoriesPeripheral equipment (reagent bottles)Instrumentation
and sensorsDESIGN OF FERMENTER
Various components of an ideal fermenter for batch process
are:
corrosion resistant
non-toxic
withstand repeated sterilization with high pressure steam
mechanical stress
Visual inspection of the medium and culture is advantageous,
transparent materials should be used Fermenter
constructioncontaminating organisms
Culture volume should remain constant
Dissolved oxygen level must be maintained above critical levels
of aeration and culture agitation for aerobic organisms
Parameters such as temperature of pH must be controlled, and the
culture volume must be well mixed. Therefore a need for control
existsOptimisation of the Fermenter System
A microbial fermentation can be viewed as a three-phase system,
involving liquid-solid, gas-solid, and gas-liquid reactions.
The liquid phase contains dissolved nutrients, dissolved
substrates and dissolved metabolites.The solid phase consists of
individual cells, pellets, insoluble substrates, or precipitated
metabolic products.The gaseous phase provides a reservoir for
oxygen supply and for CO2 removal.
Basic fermenter configurationMicrobial Growth KineticsMicrobial
Growth Kinetics describe how the microbe grows in the fermenter.
This information is important to determine optimal batch times. The
growth of microbes in a fermenter can be broken down into four
stages:Lag Phase Exponential PhaseStationary PhaseDeath Phase
Lag Phase
This is the first phase in the fermentation process and it may
be absent in certain fermentation processes.
It is a period of adaptation of the cells to their new
environment.
Cell growth is minimal in this phase. Microbial Growth
KineticsExponential Phase
This is the second phase in the fermentation process. It is also
known as log phase.
The cells have adjusted to their environment and rapid growth
takes place.
Cell growth rate is highest in this phase.
At some point the cell growth rate will level off and become
constant.
Microbial Growth KineticsThe most likely cause of this leveling
off is substrate limited inhibition.Substrate limited inhibition
means that the microbes do not have enough nutrients in the medium
to continue multiplying. Microbial Growth KineticsStationary
phase
This is the third phase in the fermentation process.
The cell growth rate has leveled off and become constant.
The number of cells multiplying equals the number of cells
dying.Microbial Growth KineticsDeath phase
The fourth phase in the fermentation process
The number of cells dying is greater than the number of cells
multiplying
The cause of the death phase is usually that the cells have
consumed most of the nutrients in the medium and there is not
enough left for sustainabilityMicrobial Growth KineticsPrimary
metabolites are produced during active cell growth (log phase)/
trophophase
Secondary metabolites are produced near the onset of stationary
phase/ idiophaseproducts which do not have an obvious role in cell
metabolismMetabolitesMetabolites
Metabolites
Penicillin was the first important commercial product produced
by an aerobic, submerged fermentationFirst antibiotic to have been
manufacture in bulk.Used as input material for some semi synthetic
antibiotics.It is fermented in a batch culture.
PRODUCTION OF PENICILLINLike all antibiotics, penicillin is a
secondary metabolite, so is only produced in the stationary
phase.
Commercial Production Of Penicillin
Improvement in composition of the mediumIsolation of better
penicillin producing mold sp. Penicillium chrysogenum which grow
better in huge deep fermentation tank.Development of submerged
culture technique for cultivation of mold in large volume of liquid
medium through which sterile air is forced.The yield of penicillin
can be increased by:
The main stages of Penicillin production are:
