Transcript File - I. Reillys Biology Class

Growth curves of
micro-organisms
Higher Level Only
Aidhm
1. Discuss the growth curves of micro
organisms
2. Outline the differences between batch
and continuous flow food processing
 How to bacteria reproduce?
 Due to the large number of bacteria
produced, we use a special scale called
the logarithmic scale to represent their
numbers.
100 = 0
101 = 10
102 = 100
103 = 1000
104 = 10,000
105 = 100,000 etc
Logarithmic scale
0
1
10
100
1,000
10,000
100,000
1,000,000
Growth curve for Bacteria
Lag phase
Log Phase
Stationary
Number of Bacteria
Logarithmic Scale
Phase
Decline
Phase
Time
Death
Phase
Growth curve for Bacteria
Lag phase
Log Phase
Stationary
Number of Bacteria
Logarithmic Scale
Phase
Decline
Phase
Adapt to new conditions
Produce the enzymes to digest the nutrients.
Time
Death
Phase
Growth curve for Bacteria
Lag phase
Log Phase
Decline
Phase
Stationary
Number of Bacteria
Logarithmic Scale
Phase
Rapid period of growth (doubles)
Time
Bacteria have enzymes and lots of nutrients.
Death
Phase
Growth curve for Bacteria
Lag phase
Log Phase
Stationary
Number of Bacteria
Logarithmic Scale
Phase
Decline
Phase
Death
Phase
Growth levels because:
•nutrients used up.
•waste is increasing.
Time
•rate of new cells produced = the rate
of cells dying.
Growth curve for Bacteria
Lag phase
Log Phase
Stationary
Death
Phase
Number of Bacteria
Logarithmic Scale
Phase
Decline
Phase
More bacteria dying because:
Time
• few nutrients left.
•bacteria are poisoned by increased waste
Lag Phase
Log Phase
Stationary
Phase
• Adapt to new conditions
• Produce the enzymes to digest the nutrients.
• Rapid period of growth (doubles)
• Bacteria have enzymes and lots of nutrients.
•Growth levels because:
•nutrients used up.
•waste is increasing.
•rate of new cells produced = the rate of cells
dying.
Decline and
Death Phase
More bacteria dying because:
• few nutrients left.
•bacteria are poisoned by increased waste
Return to graph
Learning check
1. What are the four
stages of growth of
micro-organisms
2. Explain what is
happening to the
micro-organisms at
each stage
3. What is the
significance of
endospores formation?
4. Label the diagram
Batch and Continuous Flow
food processing
A bioreactor is a vessel in which
biological reactions take place
Food processing
• Bio-processing: the use of bacteria to
produce a wide range of products.
• E.g. yoghurts and cheeses, artificial
sweeteners, flavourings, vitamins and
alcohol products such as wines and beers.
Food processing
 There are two main methods of food
processing:
 Batch food processing
 Continuous flow food processing
Batch food processing
 A fixed amount of sterile nutrient is added to the
micro-organisms in the bioreactor.
 The micro-organisms go through the stages of a
typical growth curve
 The reaction is stopped before the death stage
as very little product will be formed at this stage.
 At the end of production the product is
separated from the rest of the solution and is
purified.
Batch Processing: the growth of cells in a sealed
container over a short period of time and under ideal
conditions until all nutrients are used up
Log Phase
Stationary
Phase
Number of Bacteria
Lag phase
Time (days)
Death
Phase
Bioreactor for Batch Food Processing
Nutrients and
microorganisms
added here
Gas out here
Stirrer
Product is
released at the
end of the process
Sparger
Oxygen (if required)
in here
Continuous flow food
processing
 Nutrients are continuously fed into the
bioreactor.
 At the same time the culture medium is
continually withdrawn.
• Microorganisms stay in the Log phase
• Factors such as temperature, pH, rate of stirring,
concentration of nutrients, oxygen and waste
products are kept constant
Continuous Flow Processing: the growth of cells in
an open container, where nutrients are continuously
added and products are continuously removed.
Log Phase
Number of Bacteria
Lag phase
Time (months)
Bioreactor for Continuous Flow Food
Processing
Nutrients fed in
continuously
Gas out here
Product (and
culture medium)
flows out
continuously
Stirrer
Sparger
Oxygen
in here
Product
Learning check…
Using the diagrams below outline the differences
between batch and continuous flow food processing
Batch
processing
Continuous
flow processing
Answer
Can you….
1. Discuss the growth curves of micro
organisms
2. Outline the differences between batch
and continuous flow food processing