Chapter 22 Biotechnology and microorganisms

Question 1

What is biotechnology?

Answer 1

Applying biological organisms or enzymes to the synthesis, breakdown, or transformation of materials in service of people

e.g production of cheese, yogurt, wine, bread

Question 2

What are the advantages of using microorganisms in food processes in general?

Answer 2

No welfare issues
Able to help carry out that synthesis or degradation
Can be genetically engineered to perform a niche specific function
Short life cycles
Simple and cheap
If they supply enzymes, means processes can occur at lower temperatures

Question 3

How can you define indirect food production from bacteria?

Answer 3

The importance of microorganisms is their action of other ingredients, rather than consuming the microorganisms themselves

Question 4

What are the disadvantages of use microorganisms in indirect food production?

Answer 4

Conditions for these microorganisms to function is the same as those required for pathogenic bacteria to grow
GM bacteria used, generally GM issues
Need ideal conditions else they can produce toxins

Question 5

What is the process of baking? How are microorganisms involved?

Answer 5

Yeast aerobically respire to produce carbon dioxide, when enables the bread to rise

Yeast mixed with flour, make dough, left to prove
Dough knocked back to remove excess air
Cooked and yeast killed, bread rises

Question 6

What is the process of brewing? How are microorganisms involved?

Answer 6

Yeast anaerobically respiring to produce ethanol, GM yeast clump together to help remove them and work at lower temps

1) Malting, barley germinates, seeds killed by slow heating but retain enzyme activity
2) Mashed, and starch converted to wort by enzymes, then sterilised
3) Fermentation, inoculated with yeast, eventually respiration inhibited by the ethanol and decreased pH, lack of O2
4) Maturation, for a month, filtered, pasteurised, add in CO2

Question 7

What is the process of cheese making? How are microorganisms involved?

Answer 7

Bacteria feed on lactose in milk, inhibit growth of bacteria that spoil milk

Milk pasteurised, homogenised
Mixed with bacteria to form curds and liquid whey
Cottage cheese= curds
Other cheeses: curds cut, cooked in whey, strained, pressed

Question 8

What is the process of yogurt making?
How are microorganisms involved?

Answer 8

Bacteria produce extracellular polymers that give yogurt smooth textures

Skimmed milk powder added to milk
Pasteurised, homogenised
Milk mixed with bacteria 1:1, incubated

Question 9

What does homogenised mean? What does pasteurised mean?

Answer 9

Pasteurised: heated to kill most natural bacteria
Homogenised: enable fat droplets to be evenly distributed

Question 10

What does it mean when microorganisms can be used for direct food production?

Answer 10

We are growing microorganisms to consume them

Single cell protein- SCP- a fungus to be consumed

e.g Quorn is a mix of microorganisms, fungus, and egg whites, that we eat

Question 11

What are the advantages of using microorganisms as a food source?

Answer 11

Fast reproduction, so produce protein faster than with animals
High protein content with little fat
Helps reduce waste materials and so also reduce costs
Can be modified to produce a variety of different proteins
No welfare issues
Not dependent on weather/reproductive cycles
Can be made to taste like anything

Question 12

What are the disadvantages of using microorganisms as a food source?

Answer 12

Microorganisms may produce toxins if the right conditions are not maintained
Microorganisms must be separated from the broth
Needs sterile conditions before, only right microorganisms should grow
GM concerns
People’s opinions on consuming microorganisms

Question 13

How is penicillin made?

Answer 13

Originally from a mould which has been altered to increase yield

Small fermenters to maintain high oxygen concentration, keep stirring
Rich nutrient medium, pH 6.5 and 25-27 degrees celcius

Question 14

What is bioremediation and the two types?

Answer 14

Using microorganisms to break down pollutants and contaminants in soil/water

1) Using natural microorganisms to break down organic material, adding nutrients to the site to encourage microbial growth

2) GM MOs: e.g removal of mercury from water

Question 15

What is a culture and the two types?

Answer 15

Culture- provide conditions which promote growth
- care needed as even if strain harmless, mutations or pathogenic bacteria could contaminate

Broth- liquid
Agar-solid

Sterilise before use

Question 16

How do you inoculate broth?

Answer 16

Make bacterial suspension
Mix known volume with sterile nutrient broth in a flask
Seal flask with cotton wool to reduce contamination but enable O2 to enter
Incubate at the desired temp, shake to aerate

Question 17

How do you inoculate agar?

Answer 17

Sterilise inoculating loop by placing in dilute ethanol, then flame in the bunsen burner, then cool, then in bacterial suspension
Zigzag streak but careful not to cut through
Seal with lid, enable O2 to enter and incubate at a temp

Question 18

What are the stages of bacterial population growth?

Answer 18

Lag: as bacteria adapt to environment, start to synthesise enzymes, begin to reproduce
Log: rate of reproduction near max
Stationary: growth=0 as death rate equal to growth rate
Death: death rate greater than division begin to die- accumulation of waste reduces pH, too high amounts of intraspecific competition, and nutrients run out, cannot survive and replicate, die

Question 19

What limits bacterial growth?

Answer 19

Nutrients run out
Oxygen levels decrease but demand increases
Increased temperature causes denaturation
Accumulation of waste, toxic materials build up
Change in pH from CO2 produced

Question 20

How can you use serial dilutions to estimate bacteria population?

Answer 20

Perform serial dilution, by mixing 1cm3 of bacteria with 9cm3 of water. Then take 1cm3 from this mixture and mix with 9cm3 to dilute by 10 again. Repeat.

Then final solution, place on agar and allow to grow. Remember one final dilution as only 1cm3 taken from final solution

Count individual colonies and scale up to original

Question 21

What are primary metabolites? What are secondary metabolites?

Answer 21

Primary- substances which are formed as an essential part of normal functioning of the organism
Secondary- not essential for growth but useful e.g tannins in plants

Question 22

What is the process of batch fermentation?

Answer 22

Inoculation into a fixed volume of medium
Nutrients used up, increased biomass and waste
Stopped before death, products harvested, cleaned, sterilised, and a new batch culture starts

Question 23

What is the process of continuous fermentation?

Answer 23

Inoculated into sterile nutrient medium
Sterile medium continually added once exponential growth reached
And at the same time- culture broth is continually removed- waste, products, Mos, but vol constant
Enables balanced growth

Question 24

What is the main disadvantage of both types of fermentation?

Answer 24

All results in a mix of unused nutrient broth, MOs, metabolites, and waste products
Useful susbtances must be separated by downstream processing which costs lots of money

Question 25

What factors should be considered when running a fermenter?

Answer 25

Temperature- should promote growth but not cause denaturation
Ensure nutrients/O2 is high enough, constant testing, sensors
Mixing mechanism so nutrients and O2 can be delivered to all cells
Asepsis- must not be contained, must be sealed with GMOs, as aseptic units

Question 26

What are advantages of using isolated enzymes rather than a whole organism in processes?

Answer 26

Less wasteful as the substrate is not needed for growth
More efficient as higher concentration of enzymes can be used
More specific to a type of reaction as can be one enzyme
Easier to purify

Question 27

What are immobilised enzymes and what are the advantages of using them?

Answer 27

Enzymes attached to an inert support system and the substrate passes over them

Enzymes reused
Easily separated and cheaper to
Reliable
Greater temperature tolerance
Ease of manipulation to a process

Question 28

What are the methods used to immobilise enzymes and disadvantages of each type?

Answer 28

Adsorption to a supporting surface via hydrophilic interactions
- distortion of the active site and may detach

Covalent bonding to the surface
-expensive and distortion

Entrapment in a matrix so remain fully active
-substrate must diffuse in and product diffuse out, slower

Question 29

What are some examples where immobilised enzymes are used?

Answer 29

Glucose isomerase- glucose to fructose
Lactase- lactose to glucose/galactose, lactose-free milk
Aminocyclase- pure L amino acids, pharmaceuticals

Question 30

How do you transfer a fixed amount of liquid bacterial culture to an agar plate?

Answer 30

Wash hands and disinfect surface
Sterilise neck of the bottle by flaming in bunsen, work near a bunsen
Lift lid of a bottle at an angle
Use a sterile pipette/syringe to move the fixed volume to the agar
Use a sterile glass spreader to spread the bacteria. Close the agar but leave slightly open to allow O2
Place the spreader in disinfectant

Question 31

What are the advantages and explanations of the advantages of using microorganisms for food consumption?

Answer 31

Low cost: require low temperatures, few energy requirements
Large numbers produced quickly: short life cycle, high replication rate, meaning high yield of product
Less pollution: reduces use of land and lower energy requirements
Produced in many locations: not affected by climate, and conditions can be controlled
Healthier food: lower fat but high protein
Greater variety of uses;: can be genetically engineered for niche purposes, or to add flavour

Question 32

What measures should be taken to keep an agar plate culture sterile?

Answer 32

Work in an inoculating cabinet and maintain the minimum amount of time with the plate open
Flame inoculating loop, keep equipment sterile
Seal plates for incubation

Question 33

What practical considerations should be taken to promote growth of bacteria when in culture?

Answer 33

Provide a large supply of nutrients
Incubate at a suitable temperature
Agitation for aeration

Question 34

What things should you look out for when comparing the distribution of bacterial growth?

Answer 34

The duration of the lag phase
The rate of replication in the log phase
The duration of the stationary phase
Rate of death in the death phase comparison

Question 35

Why should Petri dishes be placed upside down when incubating?

Answer 35

Prevents the agar drying out which would reduced bacterial growth and make the results invalid

Question 36

What are economic advantages of using immobilised enzymes?

Answer 36

Reused so less cost for replacement
Downstream processing easier, so costs less
More profit from faster yield as lower temperatures so less money into this

Question 37

What are general advantages of immobilised enzymes in processes?

Answer 37

Reduced downstream processing/ extraction of the products from the enzyme is not needed
Recycling of enzyme
Increases range of temperatures enzymes can function at
Less need for emptying of bioreactors, less cleaning