Food production Microorganisms

Question 1

how can microorganisms be used by humans

Answer 1

to make food and other useful substances

Question 2

what is yeast

Answer 2

a single celled fungus which can carry out aerobic and anaerobic respiration

Question 3

when yeast is added to bread dough what does it produce

Answer 3

release enzymes that break down the starch in flour and release sugars that can be used by the yeast in respiration

Question 4

making bread: (what happens when yeast carries out respiration)

Answer 4

• when yeast carries out respiration it produces ethanol and carbon dioxide
• the carbon dioxide produced by the yeast is trapped in small air-pockets in the dough, causing it to rise
• the dough is then baled in a hot oven to form bread
• during the baking, any ethanol produced by the yeast in evaporated in the heat, so bread doesn’t contain any alcohol
• the yeast is killed by the high temperatures used during baking (ensuring no respiration occurs)

Question 5

anaerobic yeast equation

Answer 5

glucose —-> ethanol + carbon dioxide

Question 6

PRACTICAL- investigating anaerobic respiration in yeast

Answer 6

1- mix yeast with sugar solution in a boiling tube (which provides glucose o+for anaerobic res)

2- carefully add a layer of oil on top of the solution to prevent any aerobic respiration

3- using a capillary tube, connect the boiling tube with another boiling tube filled with limewater

4- place boiling tube with yeast and sugar solution into a water bath at a set temperature & count the number of bubbles produced in a fixed time

5- change the temperature of the water bath and repeat

Question 7

when yeast respires anaerobically, its called

Answer 7

fermentation

Question 8

why is bacteria useful for human use of food and other substances (2)

Answer 8

• they’re capable of producing complex molecules
• also reproduce rapidly

Question 9

how do you make yoghurt

Answer 9

• all equipment is sterilised to avoid contamination
• milk is then pasteurised at 85-95ºC to kill any other unwanted bacteria (which could slow production and ruin taste)
• milk is then cooled to 40-45ºC and Lactobacillus added
• mixture is incubated at that temp for several hours, while lactobacillus bacteria digest milk and proteins and ferments sugars in the milk
• Lactobacillus converts the lactose (sugar) into Lactic Acid and this increases acidity and thickens milk to form yoghurt
• this also prevents the growth of other organisms which could be harmful, by lowering ph acts as a preservative
• yoghurt is then stirred and cooled to 5ºC to halt Lactobacillus action
• flavourings, colourings and fruit may be added before packaging

Question 10

what are fermenters

Answer 10

containers used to grow microorganism like bacteria & fungi in large amounts

Question 11

what is an advantage of suing a fermenter

Answer 11

that conditions can be carefully controlled to produce large amounts of exactly the right type of organism

Question 12

Conditions controlling a fermenter (6)

Answer 12

• aseptic precautions
• optimum temp
• nutrients
• optimum pH
• Oxygenation
• Agitation

Question 13

Aseptic precautions

Answer 13

cleaned by steam to kill microorganisms and prevent chemical contamination, ensuring only wanted organisms grow

Question 14

nutrients (fermenter)

Answer 14

needed in respiration to release energy for growth and ensure reproduction

Question 15

optimum temperature

Answer 15

monitored using probes and maintained with water jacket, it ensures optimum temperature for enzymes

Question 16

optimum pH

Answer 16

monitored using probe, optimum value for growth of specific organism

Question 17

oxygenation

Answer 17

needed for aerobic respiration

Question 18

agitation

Answer 18

stirring paddles allow nutrients, oxygen, temp and pH and microorganisms are evenly distributed