Culturing microorganisms on an industrial scale

Question 1

What is important in any bioprocess?

Answer 1

• synthesis or breakdown the chemical required
• rapid
• give good yield
• cheap nutrients
• not require extreme / expensive conditions
• not produce posions that contaminate the product
• mutate easily into non-functioning forms

Question 2

What are primary and secondary metabolites?

Answer 2

• primary
  
  • fromed as part as an essential part of the normal functioning of a microorganism, e.g. ethanol, emzymes#
  • formed in the period of active gowth
• secondary
  
  • not essential for growth but still used by cells
  • formed in startionary phase

Question 3

What are the two ways of growing microorganisms?

Answer 3

• batch fermentation
• continuous fermenation

Question 4

What occurs in batch fermentation?

Answer 4

• microorganisms inoculated into a fixed volume of medium
• as growth takes place, nutrients are used up and both new biomass and waste products build up
• as culture reaches stationary phase, ovarall growth ceases but during this phase the microorganisms often carry out biochemical changes to form the desired product
• the process is stopped before the death phase and the nutrients are harvested
• the whole system then cleaned and sterilised and a new batch culture started up .

Question 5

What happens in continuous culture?

Answer 5

• microorganism are inoculated into sterile nutrient medium and start to grow
• sterile nutrient medium is added contunually to the culture once it reaches the exponential point of growth
• culture broth continually removed
  
  • the medium, waste products, microorganisms, and product, keeping the culture volume in the bioreactor constant
• ernables continuous balanced growth with levels of nutrients , pH and metabolic products kept more or less constant

Question 6

What do both methods of operating a bioreactor have in common?

Answer 6

• can be adjusted to ensure the maxium production of biomass or the maximum production of prumary or secondary metabolites
• downstreaming process to purify and separate the product
  
  • one of the most difficult and expensive parts

Question 7

What is continuous cultivation used for? What is the other used for?

Answer 7

• continuous
  
  • single-celled protein
  • Quorn
• most processes use batch or semi-continuous

Question 8

Why does temperature need to be controlled in the bioreactor? How is it controlled?

Answer 8

• low temp - slow reproduction
• temperature too high
  
  • enzymes denature and microorganisms inhibited or destroyed
• controlled by a heating, cooling system linked to temperature sensors and a -ve feedback system to maintain optimum conditions

Question 9

WHy does oxygen and nutrients need to be controlled? How is it controlled?

Answer 9

• oxygen and nutrient medium can be added in controlled amounts to the broth when probes or sample tests indicate levels are dropping

Question 10

WHy can’t organisms rely on simple diffusion? How is this problem overcame?

Answer 10

• large vol of liquid, may be thick and viscous due to growth
• simple diffusion not enough to ensure all microorganisms receive enough food and oxygen
• bioreactior have a mixing mechanism and are continuously stirred

Question 11

What is asepsis?

Answer 11

• if a bioprocess is contaminated by microorganisms for air or workers, yield is affected
• therefore bioreactors are sealed, aseptic units
• if they are GM organisms, there is a legal requirement they should be contained within the bioreactor and not released in the environment