section 5: cloning & biotechnology - topic 4: biotechnology - culturing microorganisms Flashcards
what is a culture?
a population of one type of microorganism that’s been grown under controlled conditions.
how are cultures grown?
they’re grown in large containers called fermentation vessels to either obtain lots of the microorganism (i.e. for production of single-celled protein) or to collect lots of a useful product that the microorganism makes.
what are the 2 main methods for culturing microorganisms?
batch fermentation.
continuous fermentation.
what is batch fermentation?
where microorganisms are grown in individual batches in a fermentation vessel - when one culture ends it’s removed and then a different batch of microorganisms is grown in the vessel.
^ this is known as a closed culture.
what is continuous fermentation?
where microorganisms are continually grown in a fermentation vessel without stopping.
nutrients are put in and waste products taken out at a constant rate.
why are the conditions inside the fermentation vessels kept at the optimum for growth?
because this maximises the yield of microorganisms and desirable products.
what are the factors that need to be controlled in a fermentation vessel?
pH.
temperature.
oxygen supply.
nutrient concentration.
contamination.
describe the control of pH.
the pH is monitored by a pH probe and kept at the optimum level.
this increases the product yield because enzymes can work efficiently, so the rate of reaction is kept as high as possible.
describe the control of oxygen supply.
the volume of oxygen is kept at the optimum level for respiration by pumping in sterile air when needed.
this increases the product yield because microorganisms can always respire to provide the energy for growth.
describe the control of nutrient concentration.
microorganisms are kept in contact with fresh medium by paddles that circulate the medium around the vessel.
this increases the product yield because microorganisms can always access the nutrients needed for growth.
describe the control of temperature.
the temperature is kept at the optimum level by a water jacket that surrounds the vessel.
this increases the product yield because enzymes can work efficiently, so the rate of reaction is kept as high as possible.
describe the control of contamination.
vessels are sterilised between uses with superheated steam to kill any unwanted organisms and make sure the next culture is not contaminated.
this increases the product yield because the microorganisms aren’t competing with other organisms.
in a closed culture, a population of microorganisms follows a…?
standard growth curve.
what is a closed culture?
when growth takes place in a vessel that’s isolated from the external environment - extra nutrients aren’t added and waste products aren’t removed from the vessel during growth.
how many phases does the growth curve have?
4.
