22.7 Culturing microorganism on an industrial scale

Question 1

what is a metabolite?

Answer 1

a substance either made or used in metabolic reactions

Question 2

what are primary metabolites?

Answer 2

substances which are formed as an essential part of a microorganism

NEEDED FOR GROWTH

Question 3

what are secondary metabolites?

Answer 3

substances that are produced by a microorganism which are not essential for growth but are still used by cells

NOT NEEDED FOR GROWTH

Question 4

examples of primary metabolite

Answer 4

ethanol
ethanoic acid
amino acids
enzymes

Question 5

examples of secondary metabolites

Answer 5

pigments
toxic chemicals to protect themselves
penicillin

Question 6

when are primary metabolites produced in a bacteria growth curve?

Answer 6

during log phase

period of active growth so metabolites needed

Question 7

when are secondary metabolites produced in a bacteria growth curve?

Answer 7

during stationary phase

produced to kill off high levels of competition in the stationary phase which is limiting growth

Question 8

describe this graph

Answer 8

during the log phase, glucose is used up which increases the biomass exponentially

however, the glucose eventually plateaus off when the stationary phase is reached

at the stationary phase, the penicillin is produced more (causes no growth)

penicillin kills competition in order to maintain the carrying capacity (but still no further growth due to lack of nutrients)

Question 9

what are the two ways of growing microorganisms?

Answer 9

batch fermentation
continuous fermentation

Question 10

batch fermentation

Answer 10

microorganism are inoculated into sterile medium
as growth occurs, nutrients are used up and biomass increases
waste products also build up

once stationary phase is reached, overall growth stops, but production of secondary metabolites such as antibiotics occur

process stopped before death phase and products are harvested

Question 11

what does batch fermentation produce and why?

Answer 11

primary and secondary metabolites

primary metabolites produced in log phase

as the nutrients are not topped up and the waste products are not removed, the microorganisms enter the stationary phase which leads to the production of secondary metabolites to deal with competition

Question 12

continuous culture

Answer 12

microorganisms are inoculate into sterile medium
as growth occurs, nutrients are used up
BUT
these nutrients are continually restored to culture during log phase

the culture broth is continually removed and products harvested

Question 13

what are the products of continuous culture?

Answer 13

primary metabolites

as the nutrients are being topped up, the microorganisms stay in log phase which means only primary metabolites are produced

Question 14

what factors need to be controlled in a bioreactors?

Answer 14

temperature
nutrients and oxygen
mixing things up
asepsis

Question 15

too low temperature

Answer 15

microorganisms will not grow fast enough

Question 16

too high temperature

Answer 16

enzymes will denature so growth is not possible

Question 17

how does a bioreactor control temperature?

Answer 17

has both a cooling and heating system which are linked to temperature sensors

runs like a negative feedback system to maintain optimum conditions

Question 18

how does a bioreactor control oxygen supply?

Answer 18

sterile air is pumped into the bioreactor

Question 19

why is an oxygen supply important in a bioreactor?

Answer 19

increases the product yield as microorganisms can always respire to provide energy for growth

Question 20

how does a bioreactor maintain nutrient concentration?

Answer 20

paddles circulate the medium in the chamber

Question 21

why is a nutrient supply important in a bioreactor?

Answer 21

increases product yield as it ensures that microorganisms always have access to nutrients needed for growth

Question 22

how is the bioreactor decontaminated?

Answer 22

sterilised using superheated steam which kills any unwanted organisms

Question 23

why is decontamination important in a bioreactor?

Answer 23

increases the product yield as microorganisms are no longer competing with unwanted organisms for resources/nutrients

Question 24

what is the mixing with the paddles for?

Answer 24

to decrease the thickness and the viscosity of the reacting liquid which allows for diffusion of nutrients

Question 25

what is asepsis in bioreactors?

Answer 25

bioreactors are sealed aseptic units which cannot be contaminated from external environment

Question 26

diagram of bioreactor

Answer 26

Question 27

how can you tell the number of microorganisms in a culture after a certain number of division?

Answer 27