Use of biological resources Flashcards
Anaerobic respiration in yeast equation
Glucose –> carbon dioxide + ethanol
How does yeast make bread rise?
Bubbles of carbon dioxide gas (produced by anaerobic respiration of yeast) expand the dough and make it rise
Why is ethanol not present in bread?
High temperatures used in bread making mean that the ethanol doesn’t remain in the bread after cooking has finished (it evaporates)
How do you measure anaerobic respiration by yeast in different conditions?
Study the production of carbon dioxide
How do you test for the presence of carbon dioxide? (2 ways)
Limewater
Hydrogencarbonate indicator
Colour of hydrogencarbonate indicator in high CO2 concentration
Yellow
Colour of hydrogencarbonate indicator in normal CO2 concentration?
Red
Colour of hydrogencarbonate indicator in normal atmospheric CO2 conentration?
Red
Describe the steps to investigating the role of anaerobic respiration in yeast in different conditions?
- Dissolve sugar in previously boiled water.
- Add yeast and mix to form a suspension.
- Add a layer of vegetable oil.
- Connect a delivery tube to a second boiling tube that contains limewater or hydrogencarbonate indicator (to test for CO2)
What bacterium is used to make yoghurt?
Lactobacillus bulgaricus
What conditions can be used to investigate anaerobic respiration in yeast?
Amount of sugar used
Temperature
Type of sugar
Steps of making yoghurt using bacteria
Milk is pasteurised
Lactobacillus bulgaricus is added
Mixture is kept at 46oC
Lactobacillus respires anaerobically producing lactic acid. This lowers the pH and and coagulates the milk protein.
Yoghurt is further cooled to 5oC to help preserve it
Why is the milk pasteurised when making yoghurt?
To kill bacteria and to prevent competition between bacteria for sugar.
Why is the mixture kept at 46oC when making yoghurt?
It is the optimum temperature for the bacteria enzymes and ensures they aren’t denatured.
How does a lower pH of yoghurt help when lactic acid is formed?
Acts as a preservative.
Air filter in fermenter purpose
Filters air coming in, maintaining sterile conditions.
Stirrers in fermenter purpose
Keeps the broth well-stirred to ensure oxygen and heat is evenly-distributed and prevent micro-organisms from settling
Cooling jacket and temperature monitor in fermenter purpose
Monitors temperature and removes heat energy, prevents the fermenter from overheating and the enzymes from denaturing. Maintains optimum temperature
Growth medium in fermenter purpose
Contains all necessary glucose and amino acids for micro-organism growth
Super-heated steam purpose in fermenters
Applied before the fermenter is used, killing unwanted micro-organisms. Leaves only water with no other residues. Maintains aseptic conditions
How is optimum temperature maintained in an industrial fermenter?
Temperature monitor and cooling jacket:
As respiration occurs in fermenter, temperature is monitored and cooling water is pumped around. Temperature is lowered maintaining optimum temp and ensuring enzymes don’t denature.
How are industrial fermenters kept aseptic?
Air filter removes dust.
Fermenter is steam cleaned before use to remove bacteria. This ensures there is no other bacteria to compete with micro-organisms added to fermenter
How is oxygen provided to industrial fermenters?
Aerator provides oxygen for respiration.
How does agitation (stirring) occur in industrial fermenters?
Stirrers mix contents to ensure oxygen and heat is evenly distributed in the fermenter and to prevent micro-organisms from settling.
How is optimum pH maintained in industrial fermenters?
pH monitor controls inlet of alkali/acid for optimum pH for enzymes.
