2. Fermentation Biotechnology
FERMENTATION
Fermentation technology is the oldest of all
biotechnological processes. The term is derived from
the Latin verb fevere, to boil--the appearance of fruit
extracts or malted grain acted upon by yeast, during
the production of alcohol.
Microbiologists consider fermentation as 'any process
for the production of a product by means of mass
culture of micro-organisms'.
Biochemists consider fermentation as ‘an anaerobic
process where energy is produced without the
3. MICRO-ORGANISMS
Several species belonging to the following categories
of micro-organisms are used in fermentation
processes:
PROKARYOTIC Unicellular: bacteria,
cyanobacteria
Colonial: cyanobacteria
EUKARYOTIC Unicellular: yeasts,
algae
Multicellular: fungi,
algae
4. Cultures of microorganisms
REQUIREMENTS FOR ARTIFICIAL CULTURE
The growth of organisms involves complex energy based
processes.
The rate of growth of micro-organisms is dependent upon
several culture and culture conditions.
Synthesis of various chemical compounds under artificial
culture, requires organism specific chemical compounds
as the growth (nutrient) medium.
Culture condition include concentrations of the
ingredients of the medium, the pH, temperature, purity of
5. Nutrient sources for industrial fermentation
Nutrient Raw material
Carbon source
Glucose Corn sugar, Starch, Cellulose
Sucrose Sugarcane, Sugar beet
molasses
Lactose Milk whey
Fats Vegetable oils
Hydrocarbons Petroleum fractions
Nitrogen source
Protein Soybean meal, Cornsteep
liquor,
Ammonia Pure ammonia or ammonium
salts
Nitrate Nitrate salts
Nitrogen Air
6. PHASES OF MICROBIAL GROWTH
When a particular organism is introduced into a
selected growth medium, the medium
is inoculated with the particular organism.
Growth of the inoculum does not occur
immediately, but takes a little while. This is
the period of adaptation, called the lag phase.
Following the lag phase, the rate of
growth of the organism steadily increases,
for a certain period--this period is
7. The phase, where the increase of the rate of
growth is checked, is the deceleration phase.
After the deceleration phase, growth ceases and
the culture enters a stationary phase or a steady
state.
Mutation of the organism in the culture can also be
a source of contamination, called internal
contamination.
The biomass remains constant, except when
certain accumulated chemicals in the
culture lyse the cells (chemolysis). Or nutrient
8. Mixed-Culture Fermentations
Mixed-culture fermentations are those in which the
inoculum always consists of two or more
organisms.
Mixed cultures can consist of known species to the
exclusion of all others, or they may be composed of
mixtures of unknown species.
The mixed cultures may be all of bacteria—or
they may consist of a mixture of fungi and bacteria
or
fungi and yeasts or
9. The earliest studies of microorganisms were
those made on mixed cultures by van
Leeuwenhoek in 1684.
Micheli, working with fungi in 1718, reported his
observations on the germination of mold spores
on cut surfaces of melons and quinces.
In 1875 Brefeld obtained pure-culture of fungi
In 1878 Koch obtained pure cultures of
pathogenic bacteria.
An early paper on mixed-culture food
10. process
Mixed cultures are the rule in nature;
therefore,
One would expect this condition to be the rule
in fermented foods of relatively ancient origin.
Soil, for example, is a mixed-organism
environment with protozoa, bacteria, fungi,
and algae
Growth in various numbers and kinds,
11. In extremely large airlift fermenters, such as the
1,500,000-liter fermenter built by Imperial
Chemical Industries, Ltd., in England for the
production of single-cell protein.
It takes a considerable amount of time for a cell
to complete a full cycle through the reactor.
12. Advantages of Mixed Culture
Product yield may be higher. Yogurt is made by the
fermentation of milk with Streptococcus
thermophilus and Lactobacillus bulgaricus .
In a mixed culture one microorganism may produce
needed growth factors or essential growth
compounds such as carbon or nitrogen sources
beneficial to a second microorganism.
It may alter the pH of the medium, thereby
improving the activity of one or more enzymes.
Even the temperature may be elevated and
13. Mixed cultures are able to bring about multistep
transformations that would be impossible for a
single microorganism.
In some mixed cultures a remarkably stable
association of microorganisms may occur. Even
when a mixture of cultures is prepared by untrained
individuals working under unsanitary conditions.
Compounds made by a mixture of microorganisms
often complement each other and work to the
exclusion of unwanted microorganisms.
14. Mixed cultures permit better utilization of the
substrate. The substrate for fermented food is always
a complex mixture of carbohydrates, proteins, and
fats.
Mixed cultures offer more protection against
contamination. In mixed-culture fermentations phage
infections are reduced.
Mixed-culture fermentations enable the utilization of
cheap and impure substrates.
Mixed cultures can provide necessary nutrients for
optimal performance with symbiosis.
15. Disadvantages of Mixed Culture
Scientific study of mixed cultures is difficult.
Defining the product and the microorganisms
employed becomes more involved in patent and
regulatory procedures.
Contamination of the fermentation is more difficult to
detect and control.
Mixed culture requires more time and space to
produce several sets of inocula rather than just one.
One of the worst problems in mixed-culture
