Microorganisms For Culturing And Immobilised Enzymes

Question 1

Advantages of using microorganisms

Answer 1

1) can grow at any climate at any time of the year so increases yeield
2) reproduces rapidly and short life cycles increasing yield in short time
3) low nutrient requirements so cheap to grow
4) can be genetically modified to fit consumer taste
5) no welfare issues

Question 2

Disadvantages of using microorganisms

Answer 2

1) can produce toxins if optimum conditions not maintained
2) needs sterile and carefully controlled conditions increasing cost
3) people have concerns about eating gm food
4) protein has to be purified
5) very little natural flavour so needs lots of additives
6) people dislike idea of eating microorganisms grown on waste

Question 3

Different ways to grow microorganisms in lab

Answer 3

1) inoculating in broth
2) inoculating in agar

Question 4

How to culture microorganisms in broth

Answer 4

1) make a suspension of bacteria to be grown in
2) mix a known volume of suspension with sterile nutrient broth in a flask
3) stopper the flask with cotton wool to prevent air contamination
4) incubate flask at suitable temperature shaking the flask to ensure broth is spread evenly

Question 5

How to culture in agar

Answer 5

1) the wire inoculating loop must be sterilised by holding in Bunsen burner until hot red and must not touch surfaces
2) dip the loop in bacterial suspension. Remove the lid of Petri dish and Make zigzag streak across agar surface
3) hold lop horizontal
4) replace lid on dish and hold down with tape but not sealed completely to allow o2 and prevent aneorobicbacteria

Question 6

Examples of aseptic techniques while culturing

Answer 6

1) disinfect any surfaces with disinfectant spray to reduce number of microorganisms
2) sterilise equipment and hold in Bunsen burner to kill any microorganisms
3) use different transfer equipment each time to prevent contamination
4) keep Petri dish closed to prevent airborne contamination
5) incubate at temperature below 37 degrees to prevent growth of pathogenic microorganisms

Question 7

Describe the bacterial growth graph

Answer 7

1) lag phase: when bacteria is adjusting to environment, synthesising enzymes for growth while rate of growth is slow
2) log phase: bacterial growth is at its maximum and growth rate is higher than death rate
3) stationary phase: increased competition, growth rate equals death rate, less nutrients available due to large number of bacteria
4) death phase: death rate is higher than growth rate, excess waste material becomes toxic and kills bacteria,

Question 8

The Two ways to culture microorganisms on industrial scale

Answer 8

1) batch fermentation
2) continuous culture

Question 9

Describe what primary metabolites are

Answer 9

• wanted substances that are essential for growth of organisms for example enzymes
• present in all stages of growth

Question 10

Describe what secondary metabolites are

Answer 10

• substances produced which are not essential for growth but are still used for example pigments
• present in log phase and stationary phase

Question 11

Describe how batch fermentation works

Answer 11

1) microorganisms are inoculated into a fixed medium volume
2) as growth rate increases, nutrients are use d up and waste builds up
3) culture reaches stationary, microorganisms carry out chemical changes to form desired end products
4) process is stopped before death phase starts
5) system sterilised and new batch culture set up

Question 12

Describe how continuous culture works

Answer 12

• Microorganims are innoculated in strerile medium to grow
• sterile nutrient medium is continuously added until log phase
• culture broth is continuously removed and helps keep culture volume constant
• allows balanced growth

Question 13

Conditions needed for bioreactor

Answer 13

• optimum temperature
• o2 concentration
• nutrient volume
• ph

Question 14

Why is using isolated enzymes good

Answer 14

1) less wasteful as whole microorganisms use up substrate growing and reproducing producing biomass rather than product
2) more efficient- they work at higher concentrations than whole microorganism
3) more specific- no unwanted enzymes present so no wasteful side reactions
4) doesn’t need purification- they already give purified product

Question 15

Why is using extra cellular enzymes good

Answer 15

• they’re secreted so easier to isolate
• each microorganism produces fewer extracellular than intracellular making them easier to identify
• more adapted to cope with temperature variation
  -however intracellular is bigger range and is cheaper

Question 16

What are immobilised enzymes

Answer 16

• enzymes attracted to an inert support system to separate products from enzymes to reuse

Question 17

Advantages of using immobilised enzymes

Answer 17

• doesn’t have to be replaced so its cheaper overall
• more reliable- higher degree of control as the support system provides stable environment
• greater temperature tolerance- enzymes less easily debated making bioreactor less expensive
• easy to manipulate- catalytic properties can be altered to fit a particular process

Question 18

Disadvantaged of immobilised enzymes

Answer 18

• less efficient
• higher initial cost- they’re more expensive than free enzymes but don’t need replacement
  -higher initial cost of bioreactor
• more technical issues - bioreactors for immobilised enzymes more complex then fermenters

Question 19

Different ways to immobilise enzymes

Answer 19

1) Surface immobilisation: adsorptiion to inorganic carriers

2) surface immobilisation: covalent or ionic bonding to carriers

3) entrapment in matrix

4) enscapulation