22.7 Culturing Microorgamism On An Indstrial Scale

Question 1

What is the difference between primary and secondary metabolites?

Answer 1

Primary: substances produced by microorganism that form an essential part of functioning of microorganism e.g. ethanol which is a product of anaerobic respiration

Secondary- products that are not essential for normal growth of microorganisms (so they wouldn’t suffer without secondary metabolites) e.g. antibiotics like penicillin

Question 2

What is a culture?
And how are they grown on a large scale?

Answer 2

• culture is a population of one type of microorganism that has been grown under controlled conditions
• cultures are grown in fermentation vessels to obtain lots of the microorganisms (e.g. single-cell protein) or to collect lots of a useful product that a microorganism makes (e.g. penicillin)

Question 3

What are the two main methods for culturing microorganisms?

Answer 3

Batch fermentation
Continuous fermentation

Question 4

Describe and explain batch fermentation

Answer 4

When microorganisms are grown in individuals batches in a fermentation vessel
When one culture ends its removed and then a different batch of microorganisms is grown in the vessel
The process is stopped before death phase and the products are harvested
The whole system is then cleaned and sterilised before a new batch culture is started up
This is known as a closed culture

Question 5

Describe and explain continuous fermentation

Answer 5

Where microorganisms are continually grown in a fermentation vessel without stopping

Nutrients are put in and waste products are taken out at a constant rate

Question 6

What factors need to be controlled in a fermentation vessel?

Answer 6

• pH (monitored by a pH probe)
• temperature
• oxygen supply (for respiration to supply energy needed for growth, O2 is supplied by pumping in sterile air)
• nutrient concentration
• contamination (vessels are sterilised between uses with superheated seam to kill any unwanted organisms and make sure next culture is not contaminated) this increases product yield because the microorganisms aren’t competing with other organisms (asepsis - the remove of unwanted microorganisms)

These conditions are kept at an optimum for growth to maximise growth of microorganisms and the yield of desirable products

Question 7

How to calculate number of cells in a population?

Answer 7

Number of cells in a population = initial number of cells x 2^n
(n is the number of division)

Question 8

What does log value of cells tell you?

Answer 8

How many times 10 has been multiplied by 10 to give you that value (makes it easier to plot large number of cells in a culture overtime)