CHAPTER 7
Media for Industrial Fermentation
Steps to Medium Development
1.
2.
3.
Design – nutritional requirements for growth and
product formation
Formulation – mass composition of cells,
stoichiometry of growth and product formation
Optimization
Media must meet the following criteria
1.
2.
3.
4.
5.
6.
It will produce a maximum yield of product at
biomass per gram of substrate used.
It will produce a maximum concentration of product
or biomass.
It will permit the maximum rate of product formation.
It will be the minimum yield of undesired product.
It will be cheap and of a consistent quality and is
readily available throughout the year.
It will cause minimal problem in other aspects of
production and agitation, extraction, purification and
waste treatment.
Macroelements
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Constitutes 90-95% of the dry weight of microbial
biomass
C, N, O, S, P, K, Mg
Microorganisms are heterotroph (obtain the cell carbon
from organic compound) and autotrophs (obtain cell
carbon from CO2)
Assimilated to provide cell carbon and energy – to
synthesize cell material, osmotic work, cell motility
Eg Penicillin production: of the total amount of glucose
consumed, 10% for carbon in biomass, 10% for energy
for biomass synthesis, 10% penicillin carbon and
energy, 70% for maintenance energy
Macroelements [cont]
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Range of C compounds: carbohydrates, alcohols,
organic acids, hydrocarbons, organic nitrogen
compounds
N requirements: generally supplied as (NH4)2SO4
Protein and peptides can be utilized if the microbes
are able to hydrolyze
Yeast extract function??
Microelements
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Ca, Mn, Fe, Cu, Co and Zn are essential
B, Cr and Mo are rarely required
Commonly added as mineral salts
Trace elements deficiencies in batch cultures are
reflected by limitation of the growth rate
In continuous culture, by the decrease observed in
the steady state biomass conc.
Must consider the interactions because optimum conc
of any ion is dependent on the conc of the others.
Growth Factors
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Some microbes require specific nutritional factors
which they cannot synthesize - growth factors
3 groups – vitamins, amino acids and miscellaneous
compounds
Water soluble vitamins – mostly coenzymes
In complex media, eg cane molasses already
contain several vitamins
Other Additives
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Precursors, eg phenylacetic acid in penicillin
biosynthesis
Stimulants, eg methanol in citric acid production
Protectants
Antifoams
Chelators – eg EDTA
Stabilizers – to avoid the loss of plasmids
Neutralizing agent – eg. Phosphate buffers
Influence of Physical Factors
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Temperature and water activity
Eg. To grow S.cereviciae at 37C instead of 30C,
the pantothenic acid content must be increased.
Pasteurella pestis requires more amino acids and
vitamins for growth at 37C than at 28C.
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The medium selected will affect the design of the fermenter
to be used.
A laboratory medium may not ideal in a large fermenter
with a low gas-transfer pattern.
Media with a high viscosity will also need a higher power
input for effective stirring.
Besides the requirement for growth and product formation,
medium may also influence pH variation, foam formation,
oxidation-reduction potential and the morphological form of
the organisms.
It may also be necessary to provide precursors or metabolic
inhibitors.
Guide to Design and Formulation for
Plant Cell Suspension Media
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The use of two-step process, first using a growth
medium and second, a production medium
C source – sucrose is preferred.
Add phytohormones to improve yield or productivity
Adding precursors to enhance secondary metabolite
formation
Growth Medium
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Select a basal medium such as MS, B5 or other
Test the medium in shake flasks and in a bioreactor
and optimize it for maximal biomass production
Production Medium
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Maintain the same carbohydrate conc of the growth
media and then test the following:
Reduce the phosphate and nitrogen content
Modify the vitamins and iron (chelated) content
Find adequate phytohormones level and their ratios
Add a precursor and find the correct time for its
addition
Test a biotic or an abiotic elicitor
Optimize the medium by fractional factorial statistical
methodology
Large Scale Media
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Take into account:
- fermenter size
- fermentation time
- purification procedure
- medium composition
before implementation!!
Can you detect the differences between plant and
animal culture media?