B: Microorganisms and Fermenters Flashcards
What are microorganisms?
organisms that are too small to see without magnification
Give 3 examples of microorganisms.
bacteria, fungi, and some protoctista
How can microorganisms also be referred to?
referred to as ‘microbes’
Why are microorganisms widely used in industry?
- metabolically diverse, therefore possible to find a type to carry out many different reactions
- very small so large numbers can be grown
- fast growth rate
What inhibits the growth of bacteria?
biocides
Describe an experiment that demonstrates the inhibition of bacteria growth using biocides.
- sterilise Petri dishes
- put nutrient agar in Petri dish
- spread a pure culture of bacterium over surface of agar
- place paper discs soaked in biocide on agar surface
- incubate dishes at optimum temperature for bacterium
- examine after 36hours
- clear areas (where bacteria died) show zones of inhibition of bacterial growth
How could you find out which antibiotics kill the bacteria causing a patient’s disease?
do the ‘experiment that demonstrates the inhibition of bacteria growth using biocides’
- just test lots of different biocides
What determines differences in bacterial resistance to biocides?
- metabolism of bacterium
- or structure of the cell wall of bacterium
What are the two main types of wall structure in bacterium?
Gram-positive and Gram-negative
What do differences in metabolism or structure of the cell wall determine?
resistance (or not) to a particular biocide
How can you deduce which type of wall structure a particular bacterium has?
do a Gram staining experiment
Outline the procedure for Gram staining.
- smear small sample of a pure bacterial culture on a microscope slide with an inoculating loop
- pass through a flame to fix the bacteria to the slide
- stain with crystal violet for 30 seconds
- treat with Gram’s iodine for 30 seconds (to bind crystal violet to the outer surface of the bacteria)
- decolorize with alcohol for 20 seconds (to dissolve the outer membrane of Gram-negative bacteria and remove the crystal violet staining)
- counterstain with safranin (which is red) for 30 seconds, then rinse and blot dry
Under the microscope Gram-negative bacteria will be red or pink. Gram-positive bacteria will be violet
In the process of Gram staining: why does one treat the bacteria with Gram’s iodine?
to bind crystal violet to the outer surface of the bacteria
In the process of Gram staining: why does one decolorize the bacteria?
to dissolve the outer membrane of Gram-negative bacteria and remove the crystal violet staining
Draw a diagram of the wall structure of Gram-positive Eubacteria. (p158)
- thick layer of peptidoglycan
2. plasma membrane of phospholipids and proteins
Draw a diagram of the wall structure of Gram-negative Eubacteria. (p158)
- thin layer of peptidoglycan
- plasma membrane of phospholipids and proteins
- outer membrane of lipopolysaccharide and protein
What is required in the large-scale production of useful substances by microbes?
fermenters
What are fermenters usually made of? Why?
- stainless steel
- to make sterilization easy
In the large-scale production of useful substances by microbes, what is the fermenter filled with?
- sterile nutrient medium
- which is inoculated with a chosen microbe
What growing conditions are relevant in the large-scale production of useful substances by microbes? Describe the conditions in a fermenter. How are the conditions monitored?
- pH and temperature
- conditions are maintained at optimal levels for the growth of the microbe
- monitored using probes and levels are adjusted if they move too far from the optimum
Why does a cooling jacket surround the fermenter?
to remove the heat energy generated as a waste product of metabolism and maintain optimum temperature conditions inside the fermenter
How does the heat jacket surrounding the fermenter work?
- cool water flows through the heat jacket and takes away the heat energy from the fermenter
Why is sedimentation of microbes prevented?
sedimentation (matter settling at the bottom of a liquid) would mean some microbes, the microbes on the bottom, would not get access to enough nutrients. This might kill them, which would be inefficient
How is sedimentation of microbes prevented?
by an impeller (a rotating set of paddles)
Why might sterile air be bubbled through the fermenter?
if the desired metabolic process is aerobic
What does a pressure gauge do in a fermenter?
measure the gas build up and allows waste gases to escape
Apart from too much/little temperature, pH and gas, what else can limit fermentation?*
*badly phrased, deal with it
other* waste products can build up and eventually limit the fermentation
*no specific ones stated
How many main types of fermentation are there?
2
What are the main types of fermentation?
- batch fermentation
- continuous culture
When are nutrients added in batch fermentation? When is the product harvested?
- once at the beginning
- when the yield has reached a maximum the fermenter is drained (to harvest the product)
When are nutrients added in continuous culture? When is the product harvested?
- nutrients added during the fermentation, so they do not run out
- product harvested during fermentation
If you’re a bit sad: Draw and label a fermenter
p158
What is the ‘useful product’ of microbes grown in fermenters called?
the metabolite of interest
What does detailed knowledge and analysis of metabolic pathways allow scientists to do? What is this called?
- change conditions at multiple points to improve the yield of the metabolite of interest
- called pathway engineering
What is pathway engineering?
change conditions in a fermenter at multiple points to improve the yield of the metabolite of interest
Give some examples of changing conditions in pathway engineering.
- extra substrate may be added
- by-products that slow down the pathway may be removed
- range of products may be extended
How is genetic engineering used in pathway engineering?
to introduce extra genes or change how the expression of existing microbial genes is regulated
