cloning and biotechnology Flashcards
1
Q
What is another name for
natural cloning?
A
Vegetative propagation
2
Q
What is vegetative
propagation?
A
A structure forms which develops into a fully differentiated new plant • Occurs in many species of flowering plants • The new plant may be propagated from the stem, leaf, bud, or root of the parent, depending on the type of plant • e.g. strawberries and spider plants
3
Q
What does vegetative
propagation often involve?
A
• Perennating organs, which enables plants to survive adverse conditions • These contain stored food from photosynthesis and can remain dormant in the soil • Often not only a means of asexual reproduction, but also a way of surviving from one growing season to the next
4
Q
Give examples of natural plant
cloning
A
Bulbs e.g. daffodil • The leaf bases swell with stored food from photosynthesis • Buds form internally, which develop into new shoots and new plants in the next growing season Runners e.g. strawberry and spider plant • A lateral stem grows away from the parent plant and roots develop where the runner touches the ground • A new plant develops, and the runner eventually withers away Rhizomes e.g marram grass • A rhizome is a specialised horizontal stem running underground, often swollen with stored food • Buds develop and form new vertical shoots which become independent plants Stem tubers e.g. potato • The tip of an underground stem becomes swollen with food to form a tuber or storage organ • Buds on this storage organ develop to produce new shoots, e.g. the ‘eyes’ on a potato
5
Q
How are natural clones used in
horticulture
A
• Splitting up bulbs, removing young plants from runners, and cutting up rhizomes all increase plant numbers cheaply • Taking cuttings of many plants and applying rooting hormone to encourage the growth of new roots
6
Q
What are the advantages and
disadvantages of using
propagation over using seeds?
A
Propagation is much faster as the time from planting to cropping is reduced • Propagation guarantees the quality of the plants as you can take cuttings from good stock and their offspring will be genetically identical • The main disadvantage is the lack of genetic variation in the offspring if a new disease or pest appears, or if climate change occurs
7
Q
Describe how sugar cane is
cloned
A
It is an internationally used crop used to make sugar and biofuels • One of the fastest growing crop plants in the world, and it is usually propagated by cloning • Short lengths of cane around 30cm long with 3 nodes are cut and buried in shallow trenches, covered with a thin layer of soil
8
Q
What is micropropagation?
A
The process of making large
numbers of genetically identical
offspring from a single parent plant
using tissue culture techniques
9
Q
When is micropropagation
used?
A
When a desirable plant: • Doesn’t readily produce seeds • Doesn’t respond well to natural cloning • Is very rare • Has been genetically modified or selectively bred with difficulty • Is required to be ‘pathogen-free’ by growers e.g. strawberries, bananas, and potatoes
10
Q
What are the steps involved in
micropropagation?
A
1. Take a small sample of tissue from the plant to be cloned. Can be leaf, stem, root or bud. Meristem tissue is often used, as this is always free from virus infection 2. This sterilised using dilute bleach, ethanol, or sodium dichloroisocyanurate Essential to kill any bacteria or fungi, as they would thrive in the conditions supplied to help the plant grow well. The material removed from the plant is called the explant 3. The explant is placed in a sterile culture medium with plant hormones (including auxins and cytokinins) which stimulate mitosis. The cells proliferate, forming a mass of identical cells called a callus 4. The callus is divided into individual cells or clumps which are transferred to a new culture medium containing a different mixture of hormones and nutrients which stimulate the development of genetically identical plantlets 5. These are potted in compost where they grow into small plants 6. The young plants are planted out to grow and produce a crop
11
Q
What are the arguments in
favour of micropropagation?
A
• Allows for the rapid production fo larger numbers of plants which will yield good crops • Culturing meristem tissue produces disease-free plants • Makes it possible to produce viable numbers of plants after genetic modification of plant cells • Provides a way of produce overlarge numbers of new plants which are seedless to meet consumer tastes (e.g. grapes) • Provides a way of growing plants which are naturally relatively infertile or difficult to grow from seed e.g. orchids • Can be used to reliably increase the numbers of rare or endangered plants
12
Q
What are the arguments
against micropropagation?
A
• Produces monoculture, and so all the plants are susceptible to the same diseases or changes in growing conditions • Relatively expensive process that requires skilled workers • The explants and plantlets are vulnerable to infection by mould and other diseases during the production process • If the source material is infected with a virus, all of the clones will also be infected • In some cases, large numbers of new plants are lost during the process
13
Q
Which type of animals is
natural animal cloning more
common in?
A
Invertebrate animals
14
Q
Give examples of natural
cloning in invertebrates
A
• Some animals (e.g. starfish) can regenerate entire animals from fragments of the original if they are damaged • Flatworms and sponges fragment and form new identical cloned animals as part of their normal reproductive process • In some insects, females can produce offspring without mating
15
Q
Give examples of natural
cloning in vertebrates
A
• The formation of monozygotic twins (identical twins) - the early embryo splits to form two separate embryos • Some female amphibians and reptiles will produce offspring when no male is available. The offspring are often male rather than female, so are not clones of their mother even though all of their genetic material comes from her
16
Q
What is artificial twinning?
A
The same as natural twinning where an early embryo splits and 2 foetuses go on to develop from the 2 halves of the divided embryo, but instead the split in the early embryo is produced manually
17
Q
What are the stages of artificial
tinning in cattle?
A
1. A cow with desirable traits is treated with hormones so she super-ovulates, releasing more mature ova than normal 2. The ova may be fertilised naturally or by artificial insemination by a bull with good traits. The the early embryos are gently flushed out of the uterus 3. Alternatively the mature eggs are removed and fertilised by bull semen in the lab 4. Around or before day 6, when the cells are still totipotent, the cells of the early embryo are split to produce several smaller embryos 5. Each of the split embryos is grown in the lab before it is implanted into a surrogate mother. Each embryo is implanted in a different mother 6. The embryos develop into foetuses and are born normally, so a number of identical cloned animals are produced by different mothers
18
Q
What is somatic cell nuclear
transfer (SCNT)?
A
A technique that involves
transferring the nucleus from a
somatic cell to an egg cell
19
Q
What are the stages in somatic
cell nuclear transfer?
A
1. The nucleus is moved from a somatic cell of an adult animal 2. The nucleus is removed from a mature ovum harvested from a different female animal of the same species (it is enucleated) 3. the nucleus from the adult somatic cell is place into the enucleated ovum and given a mild electric shock so it fuses and begins to divide. In some cases, the nucleus from the adult cell is not removed - it is simply placed next to the enucleated ovum and the two cells fuse by electrofusion and begin to divide 4. The embryo that develops is transferred into the uterus of a third animal, where it develops to term 5. The new animal is a clone from which the original somatic cell is derived, although the mitochondrial DNA will come from the egg cell
20
Q
What are the arguments for
animal cloning?
A
• It enables high-yielding farm animals to produce many more offspring than normal reproduction • Artificial twinning enables the success of a sire at passing on desirable genes to be determined • SCNT enables GM embryos to be replicated and to develop, giving many embryos from one engineering procedure • SCNT enables scientists to clone specific animals, e.g. replacing specific pets, or cloning top racehorses • SCNT has the potential to enable rare, endangered, or even extinct animals to be reproduced
21
Q
What are the arguments
against animal cloning?
A
• SCNT is a very inefficient process - in most animals it takes many eggs to produce a single cloned offspring • Many cloned animal embryos fail to develop and miscarry or produce malformed offspring • Many animals produced by cloning have shortened lifespans • SCNT has been relatively unsuccessful so far in increasing populations of rare organisms, or allowing extinct species to be brought back to life
22
Q
What is biotechnology?
A
Applying biological organisms or enzymes to the synthesis, breakdown, or transformation of materials in the service of people • Production of cheese, yogurt, wine, bread, and beer • Latest molecular technologies and using DNA manipulation to produce genetically engineered microorganisms synthesising drugs e.g. insulin and antibiotics • Use of biological systems to remove soil and water pollution in processes known as bioremediation
23
Q
What are the most commonly
used organisms in
biotechnology?
A
• Fungi, particularly the yeasts • Bacteria, which are particularly useful in the newer technologies based around genetic manipulation
24
Q
How are enzymes used in
biotechnology?
A
The most stable, convenient, and
effective form of the enzymes is
often a whole microorganism
25
Why are microorganisms ideal
| for use in biotechnology?
```
No welfare issues to consider, only
optimum conditions for growth
needed
• Large range of microorganisms
capable of carry out many different
chemical syntheses or
degradations that can be used
• Genetic engineering allows us to
artificially manipulate
microorganisms e.g. to produce
insulin
• Microorganisms have a very short
life cycle and rapid growth rate, so
huge quantities can be produce in
short periods of time
• The nutrient requirements of
microorganisms are very simple
and relatively cheap. They can be
genetically modified to use
materials that would otherwise be
wasted
• The conditions which most of
them need to grow include: a
relatively low temperature, supply
of oxygen and food, and removal
of waste gases. They provide their
own catalysts (enzymes), making
bio-processes relatively cheap
```
26
What are the disadvantages of
using microorganisms
indirectly in the production of
human food?
```
If the conditions are not ideal, the
microorganisms do not grow
properly and so don't work
efficiently
• Conditions that are ideal for the
desired microorganisms may also
be ideal for microorganisms that
cause food to go off or cause
disease, and so the processes
have to be sterile
• Some people have ethical issues
with the use of GM
```
27
Give examples of
microorganisms involved in
commercial processes
```
Baking
• Yeast - mixed with sugar and water
to respire aerobically
• CO2 produced makes bread rise
Brewing
• Yeast - respires anaerobically to
produce ethanol
• Traditional yeasts ferment at
20-28°C
• GM yeasts ferment at lower, and
therefore cheaper, temperatures,
and clump together (flocculate) and
sink at the end of the process,
leaving the beer very clear
Cheese-making
• Bacteria - feed on lactose in milk,
changing the texture and taste, and
inhibiting the growth of bacteria
which make the milk go off
Yogurt-making
• Often species that form ethanal
and lactic acid
• Both produce extracellular
enzymes that give yogurt its
smooth, thick texture
```
28
How are microorganisms used
| directly in food production?
```
Eating fungi in the form of
mushrooms
• Quorn, which is made from a
fungus
• Yeasts, algae and bacteria can be
used to grow proteins that match
animal proteins found in meat as
well as plant proteins
```
29
How is Quorn made?
```
Fusarium venetatum is a singlecelled
fungus that is grown in large
fermenters using glucose syrup as
a food source
• The microorganisms are combined
with albumen, and then
compressed and formed into meat
substitutes
```
30
What are the advantages of
using microorganisms directly
to produce human food?
```
• Microorganisms reproduce fast
and produce protein faster than
animals and plants
• Microorganisms have a high
protein content with little fat
• Micro-organisms can use a wide
variety of waste materials include
human and animal waste, reducing
costs
• Microorganisms can be genetically
modified to produce the protein
required
• Production of microorganisms is
not dependent on weather,
breeding cycles etc, and
production can be increased or
decreased to meet demand
• No welfare issues
• Can be made to taste like anything
```
31
What are the disadvantages of
using microorganisms directly
to produce human food?
```
Some microorganisms can also
produce toxins if the conditions
are not maintained at the optimum
• The microorganisms have to be
separated from the nutrient both
and processed to make the food
• Need sterile conditions that are
carefully controlled, adding to
costs
• Often involve GM organisms,
which some people have concerns
about
• The proteins has to be purified to
ensure it contains no toxin or
contaminants
• Many people dislike the though of
eating microorganisms grown on
waste
• Has little natural flavour - needs
additives
```
32
How is penicillin produced?
```
• Penicillium chrysogenum is used
• Requires relatively high oxygen
levels and a rich nutrient medium
to grow well
• A semi-continuous batch process
is used
1. The fungus grows
2. It produces penicillin
3. The drug is extracted from the
medium and purified
```
33
What are the conditions used
| to produce penicillin?
```
• Relatively small fermenters
(40-200dm3) because it is difficult
to maintain high levels of
oxygenation in large bioreactors
• The mixture is continuously stirred
to keep it oxygenated
• There is a rich nutrient medium
• The growth medium contains a
buffer to maintain pH at 6.5
• The bioreactors are maintained at
25-27°C
```
34
What was the problem with
extracting insulin from the
pancreas of animals?
```
The animals were usually pigs or
cattle, slaughtered for meat
• Meant the supply was erratic
because it depended on the
demand for meat
• Some people were allergic to the
animal insulin as it was often
impure
• The peak activity of animal insulin
is several hours after it’s been
injected, which made calculating
when to eat meals difficult
• For some faith groups, using pig
products is not permitted
```
35
How has the production of
| insulin changed?
The bacteria are grown in a
fermenter and downstream
processing results in a constant
supply of pure human insulin
36
What happens in
| bioremediation?
```
Microorganisms are used to break
down pollutants and contaminants
in the soil or in water
• Two different approaches: using
natural organisms and using GM
organisms
```
37
How are natural organisms
| used in bioremediation?
```
Many microorganisms naturally
break down organic material
producing CO2 and water
• Soil and water pollutants are often
biological, e.g. sewage and crude
oil
• If these naturally occurring
microorganisms are supported,
they will break down and
neutralise many contaminants
• e.g. in an oil spill, nutrients can be
added to the water to encourage
microbial growth
```
38
How are GM organisms used in
| bioremediation?
```
• Scientists are trying to develop
GM bacteria which can break
down or accumulate contaminants
which they would not naturally
encounter
• e.g. bacteria have been
engineered that can remove
mercury contamination from water
```
39
Why must health and safety
procedures be followed when
culturing microorganisms in a
laboratory?
```
• There is always the risk of a
mutation making the strain
pathogenic
• There may be contamination with
pathogenic microorganisms from
the environment
```
40
What are the conditions
needed to culture
microorganisms?
```
• The right conditions of
temperature, oxygen and pH
• Nutrient medium (food) which is
either in liquid form (broth) or in
solid form (agar)
```
41
Describe the nutrient medium
```
• Nutrients are often added to the
agar or the broth to provide a
better medium for microbial
growth
• Some microorganisms need a
precise balance of nutrients but
often the medium is simply
enriched with good protein
sources e.g. blood, yeast extract
or meat
• Enriched nutrient media allow
samples containing a very small
number of organisms to multiply
rapidly
• The nutrient medium must be kept
sterile until it is ready for use
• Aseptic techniques are important
```
42
What happens once the agar or
nutrient broth has been
prepared?
The bacteria must be added in a
| process called inoculation
43
What are the steps in
| inoculating broth?
```
1. Make a suspension of the
bacteria to be grown
2. Mix a known volume with the
sterile nutrient broth in the flask
3. Stopper the flask with cotton
wool to prevent contamination
from the air
4. Incubate at a suitable
temperature, shaking regularly to
aerate the broth providing
oxygen for the growing bacteria
```
44
What are the steps in
| inoculating agar?
```
1. The wire inoculating loop must
be sterilised by holding it in a
Bunsen flame until it glows red
hot. It must not be allowed to
tough any surfaces as it cools to
avoid contamination
2. Dip the sterilised loop in the
bacterial suspension. Remove
the lid of the Petri dish and make
a zig-zag streak across the
surface of the agar. Avoid the
loop digging into the agar, as the
surface of the agar must be kept
intact
3. Replace the lid of the Petri dish.
It should be held down with tape
but not sealed completely so
oxygen can get in, preventing
the growth of anaerobic bacteria.
Incubate at a suitable
temperature
```
45
What stops the unlimited
growth of bacteria in closed
systems?
Limited nutrients and a build-up of
waste products always stops
reproduction and growth eventually
46
What are the 4 stages of the
| bacteria growth curve?
```
Lag phase: when bacteria are
adapting to their new environment.
They are growing, synthesising the
enzymes they need, and are not
yet reproducing at their maximum
rate
• Log/exponential phase: when the
rate of bacterial reproduction is
close to or at its theoretical
maximum
• Stationary phase: when the total
growth rate is zero. The number of
new cells formed by binary fission
is cancelled out the number of
cells dying
• Decline/death phase: when
reproduction has almost ceased
and the death rate of cells is
increasing
```
47
What are the limiting factors
that prevent exponential
growth in a culture of bacteria?
```
• Nutrients available: As the
number of organisms multiply,
nutrients are used up and the level
will become insufficient to support
further growth and reproduction
unless more nutrients are added
• Oxygen levels: As the population
rises, so does the demand for
respiratory oxygen so oxygen
levels can become limiting
• Temperature: Enzyme-controlled
reactions are affected by the
temperature of the culture
medium. For most bacteria high
temperature speeds up growth
and reproduction. If the
temperature gets too high, it will
denature the enzymes, killing the
microorganisms
• Build-up of waste: As bacterial
numbers rise, the build-up of toxic
material may inhibit further growth
and can even poison and kill the
culture
• Change in pH: As CO2 produced
by the respiration of bacterial cells
increases, the pH of the culture
falls until a point where the low pH
affects enzyme activity and inhibits
population growth
```
48
What are the requirements for
a microorganisms involved in
any bioprocess?
```
It must be able to synthesise or
break down the chemical required
• Work reasonably fast
• Give a good yield of the product
• Use relatively cheap nutrients
• Not require extreme (expensive)
conditions
• Must not produce any poisons that
contaminate the product
• Must not mutate easily into nonfunctioning
forms
```
49
What are primary metabolites?
```
Substances that are wanted which
are formed as an essential part of
the normal functioning o a
microorganism
• e.g. ethanol, ethnic acid, amino
acids, and enzymes
```
50
What are secondary
| metabolites?
```
Substances which are produced by
organisms that are not essential for
normal growth, but are still used by
the cells
• e.g. pigments and the toxic
chemicals plants use to protect
themselves against attack by
herbivores
• The organisms would not suffer (at
least in the short term) without
them
• e.g. penicillin and many other
antibiotics
```
51
What are the 2 main types of
| bioprocess?
```
• Batch fermentation and
Continuous fermentation
• Both methods can be adjusted to
ensure either the maximum
production of biomass, or the
maximum production of the
primary or secondary metabolites
• The majority of industrial
processes use batch or semicontinuous
• Continuous is largely used for the
production of single-celled protein
and in some waste water
treatment processes
```
52
What are the steps in batch
| fermentation?
```
1. The microorganisms are
inoculated into aa fixed volume
of medium
2. As growth takes place, nutrient
are used up, and both new
biomass and waste products
build up
3. As the culture reaches the
stationary phase, overall growth
ceases, but during this phase
the microorganisms often carry
out biochemical changes to form
the desired end products (e.g.
antibiotics and enzymes)
4. The process is stopped before
the death phase, and the
products are harvested.
5. The whole system is cleaned
and sterilised, and a new batch
culture is started up
```
53
What are the steps in
| continuous culture?
```
1. Microorganisms are inoculated
into the sterile nutrient medium
and start to grow
2. Sterile nutrient medium is added
continually to the culture once it
reaches the exponential point of
growth
3. Culture broth is continually
removed - the medium, waste
products, microorganisms, and
product - keeping the culture
volume in the bioreactor
constant
This enables continuous balanced
growth, with levels of nutrients, pH
and metabolic products kept more
or less constant
```
54
What is common to all
| bioreactors?
```
• Producing a mixture of unused
nutrient broth, microorganisms,
primary metabolites, possibly
secondary metabolites, and waste
products
• The useful part of the mixture has
to be separated out by
downstream processing - this is
one of the most difficult and
expensive parts of the whole
process
```
55
What are the factors that need
| to be controlled in bioreactors?
```
Temperature
• If it’s too low the microorganisms
will not grow quickly enough
• If it’s too high, enzymes will
denature and the microorganisms
will be inhibited or destroyed
• Bioreactors often have a heating/
cooling system linked to
temperature sensors, and a
negative feedback system to
maintain optimum conditions
Nutrients and oxygen
• Oxygen and nutrient medium can
be added in controlled amounts to
the broth when probes or sample
tests indicate that levels are
dropping
Mixing things up
• Inside the bioreactor there are large
volumes of liquid, which may be
thick and viscous due to the growth
of microorganisms
• Simple diffusion is not enough to
ensure that all the microorganisms
receive enough food and oxygen
• Most bioreactor have a mixing
mechanisms and many are stirred
continuously
Asepsis
• If a bioprocess is contaminated by
microorganisms from the air, or
from workers, it can seriously affect
the yield
• To solve this problem, most
bioreactors are sealed aseptic units
• If the process involves GM
organisms, they must legally be
contained within the bioreactor and
not released into the environment
```
56
What are the advantages of
using isolated enzymes instead
of whole organisms in
biotechnological processes?
```
• Less wasteful: Whole
microorganisms use up substrate
growing and reproducing,
producing biomass rather than
product. Isolated enzymes do not
• More efficient: Isolated enzymes
work at much higher
concentrations than is possible
when they are part of the whole
microorganism
• More specific: No unwanted
enzymes present, so no wasteful
side reactions take place
• Maximise efficiency: Isolated
enzymes can be given ideal
conditions for maximum product
formation, which may differ from
those needed for the growth of the
whole organism
• Less downstream processing:
pure product is produced by
isolated enzymes. Whole
microorganisms give a variety of
products in the find broth, making
isolation of the desired product
more difficult and therefore
expensive
```
57
Why are extracellular enzymes
easier and cheaper to use
than intracellular enzymes?
```
• Extracellular enzymes are
secreted, making them easy to
isolate and use
• Each microorganism produces
relatively few extracellular
enzymes, making easy to identify
and isolate the required enzyme ,
meanwhile hundred of intracellular
enzymes are produced
• Extracellular enzymes tend to be
more robust. Conditions outside a
cell as less tightly controlled, so
extracellular enzymes are adapted
to cope with greater variation in
temperature and pH than
intracellular enzymes
```
58
Why are intracellular enzymes
| sometimes used anyway?
```
• There is a bigger range of
intracellular enzymes, so in some
cases they provide the ideal
enzyme for a process
• The benefits of using a very
specific intracellular enzyme may
outweigh the disadvantages
• e.g. glucose oxidase for food
preservation
• e.g. asparaginase for cancer
treatment
• e.g. penicillin acylase for
converting natural penicillin into
semi-synthetic drugs which are
more effective
```
59
Why is using free enzymes
| often very wasteful?
```
Enzymes are not cheap to produce,
but at the end of the process they
cannot usually be recovered, and so
they are simply lost
• To combat this, enzymes used in
industrial processes are
immobilised
```
60
Describe immobilised enzymes
```
• They are attached to an inert
support system over which the
substrate passes and is converted
to product
• Technology is mimicking nature,
because enzymes is cells are
usually bound to membranes to
carry out their repeated cycles of
catalysis
• As the enzymes are held
stationary, they can be recovered
from the reaction mixture and
reused
• The enzymes don’t contaminate
the end product, so less
downstream processing is needed
```
61
What are the advantages of
| using immobilised enzymes?
```
• They can be reused which is
cheaper
• They are easily separated from the
reactants and products, so less
downstream processing which is
cheaper
• More reliable as there is a high
degree of control over the process
as the insoluble support provides a
stable microenvironment
• Greater temperature tolerance as
immobilised enzymes are less
easily denatured by heat and work
at optimum levels over a wider
range of temperatures, making the
bioreactor less expensive to run
• Ease of manipulation - the catalytic
properties of immobilised enzymes
can be altered to fit a particular
process more easily than those of
free enzymes
```
62
What are the disadvantages of
| using immobilised enzymes?
```
• Reduced efficiency - the process
of immobilising an enzyme may
reduce its activity rate
• Higher initial costs of materials -
immobilised enzymes are more
expensive than free enzymes or
microorganisms. However, the
immobilised enzymes, unlike free
enzymes, don’t need to be
replaced frequently
• Higher initial costs of bioreactor -
the system needed to use
immobilised enzymes is different
from traditional fermenters so there
is an initial investment cost
• More technical issues - reactors
which used immobilised enzymes
are more complex than simple
fermenters as they have more
things that can go wrong
```
63
Describe surface
| immobilisation by adsorption
```
Adsorption to inorganic carriers,
e.g. cellulose, silica, carbon
nanotubes, and polyacrylamide gel
Advantages
• Simple and cheap to do
• Can be used with many different
processes
• Enzymes are very accessible to
substrate and their activity is
virtually unchanged
Disadvantages
• Enzymes can be lost from matrix
relatively easily
```
64
Describe surface
immobilisation by covalent or
ionic bonding to inorganic
carriers
```
Covalent bonding e.g. carriers with
amino, hydroxyl, carboxyl groups
Ionic bonding e.g. polysaccharides
such as cellulose, synthetic
polymers
Advantages
• Cost varies
• Enzymes strongly bound and
therefore unlikely to be lost
enzymes very accessible to
substrate
• pH and substrate concentration
often have little effect on enzyme
activity
Disadvantages
• Cost varies
• Active site of the enzyme may be
modified in the process, making it
less effective
```
65
Describe entrapment in matrix
```
In matrix e.g. polysaccharides,
gelatin, activated carbon
Advantages
• Widely applicable to different
processes
Disadvantages
• May be expensive
• Can be difficult to entrap
• Diffusion of the substrate to and
product from the active site can be
slow and hold up the reaction
• Effect of entrapment on enzyme
activity very variable, depending
on matrix
```
66
Describe membrane
| entrapment
```
Membrane in microcapsules
(encapsulation) or being a semipermeable
membrane, e.g. polymerbased
semi-permeable membranes
Advantages
• Relatively simple to do
• Relatively small effect on enzyme
activity
• Widely applicable to different
processes
Disadvantages
• Relatively expensive
• Diffusion of the substrate to and
product from the active site can be
slow and hold up the reaction
```
67
When are immobilised
| enzymes used?
When large quantities of product are
wanted, because they allow
continuous production
68
Give examples of the use of
| immobilised enzymes
```
Penicillin acylase
• Used to make semi-synthetic
penicillins from natural penicillins
• Many types of bacteria have
developed resistance to naturally
occurring penicillins, but are still
vulnerable to semi-synthetic
penicillins
Glucose isomerase
• Converts glucose to fructose
• Fructose is much sweeter than
sucrose or glucose and is widely used
as a sweetener in the food industries
Lactase
• Hydrolyses lactose to glucose and
galactose to produce lactose-free milk
Aminocyclase
• To produce pure samples of L-amino
acids used in the production of
pharmaceuticals, organic chemicals,
cosmetics and food
Glucoamylase
• Used to complete the breakdown of
start to glucose syrup
• Amylase enzymes break starch down
into short chain polymers called
dextrins
• The final breakdown of dextrins to
glucose is catalysed by immobilised
glucoamylase
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