Bio paper 2

Created by

Sofia Dinvalde

Cards (139)

what is a culture
a population of one type of microorganism thats been grown under controlled conditions
what are the 2 main methods for culturing microorganisms
- batch fermentations
- continuous fermentation
what is batch fermentation
- where microorganisms are grown in individual batches in a fermentation vessel
- when one culture ends its removed and then a different batch of microorganisms is grown in the vessel
- 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 are taken out at a constant rate
why are the conditions inside the fermentation vessel kept at the optimum
- for growth
- this maximises the yield of microorganisms and desirable products
which factors need to be controlled in a fermentation vessel
- pH
- temperature
- oxygen supply
- nutrient concentration
- contamination
how is pH monitored in a fermentation vessel and why
- by a pH probe
- kept at optimum level
- increases the product yield because enzymes can work efficiently, so the rate of reaction is kept as high as possible
how is temperature controlled in a fermentation vessel and why
- 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
how is oxygen supply controlled in a fermentation vessel and why
- vol. of O2 kept at optimum level for respiration by pumping in sterile air when needed
- this increases product yield because microorganisms can always respire to provide the energy for growth
how is nutrient concentration controlled in a fermentation vessel and why
- microorganisms are kept in contact with fresh medium by paddles that circulate the medium around the vessel
- this increases product yield because microorganisms can always access the nutrients needed for growth
what would happen if you didnt have paddles stirring the medium in a fermentation vessel
the nutrients would all sink to the bottom and the nutrient conc. wouldnt be the same throughout the vessel
how is contamination controlled in a fermentation vessel and why
- 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 arent competing with other organisms
what is an open culture
if a culture isnt isolated from the external environment
what is a closed culture
when growth takes place in a vessel thats isolated from the external environment - extra nutrients arent added and waste products arent removed from the vessel during growth
what are the four phases of a standard growth curve
- lag phase
- exponential (log) phase
- stationary phase
- decline phase
what happens in the lag phase
- the population size increases very slowly because the microorganisms have to make enzymes and other molecules before they can reproduce
- this means the reproduction rate is slow
what happens in the exponential (log) phase
- the population size increases quickly because the culture conditions are at their most favourable for reproduction (lots of food and little competition)
- the number of microorganisms doubles at regular intervals
what happens in the stationary phase
- the population size stays level because the death rate of the microorganisms equals their reproductive rate
- microorganisms die because theres not enough food and poisonous waste products build up
what happens in the decline phase
- the population size falls because the death rate is greater than the reproductive rate
- this is because food is very scarce and waste products are at toxic levels
what is the equation for estimating the number of cells in a culture
N = No X 2^n

N = number of cells present in a population
No = the initial number of cells
n = the number of divisions
what is the generation time
the time between divisions - the time taken for the cells to divide and reproduce
how are cultures of microorganisms grown in the lab
- on an agar plate - a sterile petri dish containing agar jelly
- nutrients can be added to the agar to help improve the growing conditions
- to culture the microorganisms use a sterile implement like a wire inoculation loop to transfer some of the sample to the plate
- gently spread across the whole surface of the agar
- the plates then need to be incubated to allow the microorganisms to grow
why are aseptic techniques important when culturing microorganisms
- prevents contamination of cultures by unwanted microorganisms which may affect the growth of the microorganism being cultured
- contaminated cultures in lab experiments give imprecise results and may be hazardous to health
- contamination on an industrial scale can be very costly because entire cultures may have to be thrown away
what are some important aseptic techniques
- regularly disinfect work surfaces
- work near a bunsen flame. hot air rises so any microorganisms in the air should be drawn away from culture
- sterilise the instrument used to transfer cultures before and after each use
- minimise the time that the agar plate is open
- briefly pass the neck of the broth container through a bunsen burner flame just after its opened and just before its closed which causes air to move out of the container preventing unwanted organisms from falling in
what do log numbers show
the log of a number tells you how many times 10 has been multiplied by 10 to give you that number
how is this issue solved: due to the rapid growth rate of microorganisms, the number of cells present after the exponential growth phase can vary massively from the number present at the beginning. this means that plotting the number of cells in a culture over time would be really difficult to do on a normal scale because the y-axis would have to cover a really wide range of values
logarithms are used
why should agar plates me incubated upside down
this stops any condensation forming on the lid from dropping onto the agar
what is a colony
a large group of microorganisms, which usually originate from a single cell, living closely together on the agar
- colonies are visible to the naked eye
what are serial dilutions
a set of dilutions that decrease in conc. by the same factor each time
what are primary metabolites
substances which are formed as an essential part of the normal functioning of a microorganism
- e.g. ethanol, ethanoic acid and a range of amino acids and enzymes
what are secondary metabolites
- substances which are not essential for normal growth, but are still used by the cells
- e.g. pigments, and the toxic chemicals plants produce to protect themselves against attack by herbivores
- the organism would not suffer short term without them
describe what happens in batch fermentation
- the microorganisms are 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 the culture reaches the stationary phase, overall growth ceases but during this phase the microorganisms often carry out biochemical changes to form the desired end products (like antibiotics and enzymes)
- the process is stopped before the death phase and the products are harvested. the whole system is then cleaned and sterilised and a new batch culture started up
describe what happens in continuous fermentation
- microorganisms are inoculated into sterile nutrient medium and start to grow
- sterile nutrient medium is added continually to the culture once it reaches the exponential point of growth
- culture broth is continually removed - the medium, waste products, microorganisms and product keeping the culture volume in the bioreactor constant
what is biotechnology
the industrial use of living organisms (or parts of living organisms) to produce food, drugs and other products
- the living organisms used are mostly microorganisms (bacteria and fungi)
why are mostly microorganisms used in biotechnology
- their ideal growth conditions can be easily created, microorganisms will generally grow successfully as long as they have the right nutrients, temperature, pH, moisture levels and availability of gases
- due to their short life-cycle they grow rapidly under the right conditions so products can be made quickly
- they can grow on a range of inexpensive materials - makes them economical to use
- can be grown at any time of the year
how is lactase produced and why
- prepared from Aspergillus fungi
- used in the production of lactose-free products
what are isolated enzymes
Enzymes that aren't contained within cells
how are microorganisms used in brewing (making beer)
- yeast added to a type of grain (such as barley) and other ingredients
- the yeast respires anaerobically using the glucose from the grain and produces ethanol and CO2=fermentation
how are microorganisms used in baking
- yeast makes bread rise
- the CO2 produced by fermentation of sugars in the dough makes sure it doesnt stay flat
- flat breads made without yeast
how are microorganisms used in cheese making
- used to rely on a substance called rennet which contains the enzyme chymosin that clots of milk
- traditionally chymosin was obtained by extracting rennet from the lining of calves' stomachs but now chymosin obtained from GM yeast cells
- also involves lactic acid bacteria
- these bacteria convert the lactose in milk into lactic acid which makes it turn sour and contributes to it solidifying
- the production of blue cheeses also involves the addition of fungi