Learner Resource 4 –
Biotechnology summary
Definition: The industrial use of living organisms or parts of living organisms to produce food, drugs
or other products.
Type of
product
Example
Organism used
yeast
Food
ethanol, e.g. in brewing beer and
making wine
carbon dioxide, e.g. in bread
lactic acid, e.g. in yogurt and cheese
mycoprotein
Drugs
penicillin
other antibiotics
insulin, other therapeutic human proteins
Penicillium fungus
other fungi and bacteria
GM bacteria
Other products
methane as ‘biogas’
citric acid, E330, a food preservative
anaerobic decomposer bacteria
Aspergillus fungus
yeast
Lactobacillus bacteria
Fusarium fungus
The benefits of using microorganisms to make certain products are:
1. The reactions take place at lower temperatures than would be required to make the
molecules by chemical means. This saves money (and fuel – synoptic link to sustainable
management, 6.3.2)
2. The reactions take place at lower pressures than would be required to make the molecules
by chemical means. This is safer.
3. The microbes are fed waste products from other food industries, e.g. starch water waste,
molasses.
4. Microbes reproduce quickly, building up large populations within a vessel (fermenter).
5. Microbes can be genetically engineered (link to 6.1.3).
6. In some cases the products are purer or easier to separate than in conventional chemical
methods. This means lower downstream processing costs.
For these reasons microorganisms are also used in bioremediation, cleaning up land or water
contaminated with pollutants such as oil, arsenic and toxic ions of mercury.
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Microorganisms are not the only organisms used in biotechnology. Genetically modified mammals
such as sheep and goats are also used to produce useful proteins, which are harvested in their milk.
Sometimes enzymes extracted from organisms are used instead of whole organisms. In this case
the enzymes are usually immobilised, to make downstream purification of the product easier and to
allow the enzymes to be recovered and used again. Also immobilised enzymes are more stable and
less susceptible to having their activity reduced by pH and temperature change. The main methods
of enzyme immobilisation are:
1 Entrapping the enzyme molecules in alginate balls or a network of cellulose fibres.
2 Adsorption – sticking the enzymes to porous beads of clay, resin or glass.
3 Separation of the enzyme and substrate by a partially permeable membrane.
There is synoptic overlap with 6.3.2, population growth, when looking at the standard growth curve
of microbes in a closed culture. The same key phases – A lag phase, B log phase, C stationary
phase (births = deaths) are seen, and a decline phase D where deaths exceed births may also be
seen.
C
D
Log
number
of
bacteria
B
A
Time
When growing microbes in a fermenter the key distinction to note is:
Continuous culture – nutrients are continually added and the product regularly harvested. This
keeps the culture in the log phase of growth. This maximises production of primary metabolites or of
the microorganisms themselves.
Batch culture – the fermenter is set up with a fixed quantity of nutrients and is then left. The culture
reaches the stationary phase, when secondary metabolites are made, and then the product is
harvested.
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As nutrients, oxygen and an ideal temperature for the growth of microbes is provided in a fermenter,
it is important to exclude other microorganisms that would compete for resources, slowing the
growth of the wanted microorganism, or that would contaminate the product, possibly making it
unsafe to use if the unwanted bacteria made toxic chemicals. A contaminated batch would have to
be thrown away, losing the industrial company money. Aseptic techniques are used to prevent
contamination, such as sterilising all equipment with disinfectant chemicals or by steam-cleaning.
Equipment is made of polished stainless steel to make it easy to clean. Nutrient media are sterilised
by heating before use. Air filters may be used in the workplace and at pipe inlets to stop microbes
entering.
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