B: Microorganisms in Industry

Question 1

Who discovered penicillin. When did they discover it? How did they discover it? What is this called in biology?

Answer 1

• Alexander Flemming
• 1920s

by chance:

• Petri dish growing bacteria
• bacteria contaminated with Penicillium
• bacterial colonies near fungus died out
• Fleming realised chemical produced by fungus was acting as a biocide

chance discovery is called ‘serendipity’

Question 2

When was a method for mass-producing penicillin developed? What was the method called?

Answer 2

• 1940s

called deep-tank fermentation

Question 3

What is an obligate aerobe?

Answer 3

an organism that requires oxygen to grow

Question 4

Penicillium is an obligate aerobe. What is the significance of this when growing Penicillium?

Answer 4

oxygen must be bubbled through the fermenter, with paddles to distribute it evenly
(otherwise it will die)

Question 5

What are the optimum conditions for Penicillium? What is the nutrient source for Penicillium?

Answer 5

• oxygen must be present
• 24°C
• slightly alkaline pH
• corn steep liquor

Question 6

When is penicillin produced by Penicillium? What do we call this kind of production? What type of fermentation, therefore, is used to produce penicillin?

Answer 6

• only produced if nutrient concentrations are low
• secondary metabolite (organic compounds that are not directly involved in the normal growth, development, or reproduction of an organism)
• batch culture

Question 7

What can be said of initial nutrient concentrations when mass-producing penicillin? Why are they like this?

Answer 7

• nutrient concentrations are high

- to stimulate the fungus to grow

Question 8

What has happened after about 30 hours since the start of the batch culture production of penicillin? What is the effect of this event? Why does this happen?

Answer 8

• nutrient concentrations have dropped
• penicillin production starts and continues for about 6 days
• penicillin is produced by Penicillium when nutrient concentrations are low

Question 9

When is the batch culture production of penicillin fermenter drained? What happens after drainage?

Answer 9

• 6 days after the process began

- liquid from fermenter filtered and then solvents are used to precipitate the penicillin

Question 10

What is citric acid? How is it used?

Answer 10

• it is a food additive

- used as a flavour enhancer and preservative

Question 11

What does industrial production of citric acid rely on?

Answer 11

the fungus - Aspergillus niger

Question 12

How is most citric acid industrially produced? Can it be produced any other way?

Answer 12

• mostly batch fermentation

- sometimes continuous fermentation

Question 13

What are the optimal conditions for the industrial production of citric acid?

Answer 13

• high dissolved oxygen
• sugar concentrations
• acidic pH
• 30°C

Question 14

Citric acid is produced in a cell cycle. What would we therefore call citric acid? Which cell cycle is citric acid produced in?

Answer 14

• primary metabolite

- Krebs cycle

Question 15

Under what conditions does citric acid build up?

Answer 15

if culture is undersupplied with minerals such as iron

Question 16

In continuous fermentation, how can citric acid be harvested?

Answer 16

by draining off fluid, filtering, then precipitating citric acid by adding calcium hydroxide

Question 17

Define ‘proteome’.

Answer 17

the complete set of proteins that it can produce

Question 18

What does the proteome depend on?

Answer 18

the genes that are in the genome

Question 19

How can the proteome be altered?

Answer 19

by genetic engineering - a new gene is added to the genome, which is expressed to produce a protein not previously in the proteome

Question 20

When is an organism said to be ‘transgenic’?

Answer 20

if it has been genetically modified with a gene from another organism

Question 21

Through genetic engineering, a gene can be added to the genome, which is expressed to produce a protein not previously in the proteome. What is this new gene called?

Answer 21

the target gene

Question 22

What must the target gene do if the transgenic organism is to be useful?

Answer 22

target gene must be expressed at an appropriate rate when required and not at other times

Question 23

How is appropriate expression of the target gene achieved?

Answer 23

by linking it to other base sequences that control its expression

Question 24

What are marker genes? Give an example.

Answer 24

• genes that are linked up to the target gene to indicate whether the target gene has been uptaken successfully by the intended transgenic organism
• marker gene example: gene for antibiotic resistance - cells that have not successfully uptaken target gene will be killed when treated with the antibiotic

Question 25

What makes it relatively easy to find target genes in other species?

Answer 25

bioinformatics

Question 26

What is biogas?

Answer 26

the combustible gas produced in a fermenter by the anaerobic breakdown of organic matter

Question 27

Name 3 sources of biogas.

Answer 27

manure, waste plant matter from crops and household organic waste

Question 28

What is biogas mostly comprised of? What does this depend on?

Answer 28

• methane with some carbon dioxide

- the construction of the fermenter

Question 29

Outline the series of processes carried out by the different bacteria in a biogas generator.

Answer 29

1) conversion of raw organic waste into organic acids, alcohol, hydrogen, and CO2
2) conversion of organic acids and alcohol to ethanoic acid, carbon dioxide and hydrogen
3) production of methane by reducing CO2 with hydrogen or splitting ethanoic acid

Question 30

What are methanogens?

Answer 30

bacteria that produce methane

Question 31

Draw a diagram of a simple biogas generator (p159)

Answer 31

1. mylar balloon (basically helium party balloons)
2. glass connector tubes
3. tube clamps
4. rubber tube
5. plastic feedstock bottle (not glass to minimise risk of explosion)

Question 32

What is a reading frame?

Answer 32

a sequence of consecutive, non-overlapping codons in DNA or RNA

Question 33

How many possible reading frames are there in any piece of DNA or RNA? What

Answer 33

three

Question 34

What determines which reading frame should be used on a piece of DNA or RNA?

Answer 34

the start codon

Question 35

What is an ORF?

Answer 35

open reading frame

Question 36

What is an open reading frame?

Answer 36

a length of DNA from a start codon to a stop codon that is long enough to code for a polypeptide

Question 37

How many triplets of nucleotides (codons) are usually expected in an ORF?

Answer 37

100+ triplets