(5.5-5.9B) Microorganisms + Fish farming

What is yeast?

A single-celled fungus that can carry out both aerobic + anaerobic respiration

What does yeast produce when respiring anaerobically?

ethanol + carbon dioxide

Describe the use of yeast in making bread.

Yeast produces enzymes that break down starch in flour to sugars

Yeast uses sugars to respire aerobically and switches to anaerobically when O2 runs out

During anaerobic respiration, it produces ethanol and CO2

CO2 is trapped in small air pockets, making the bread rise

Ethanol is evaporated during baking

Yeast is killed during baking

Describe how to test the effect of temperature on yeast fermentation.

• Mix yeast and sugar solution in a boiling tube.

• Add oil to the top- anaerobic.

• Connect to another boiling tube with limewater

• Place the first tube into water bath and count the number of bubbles produced in a fixed time.

  • rate of CO2 = rate of respiration

• Repeat with different water bath temperatures.

What role does lactobacillus play in the production of yoghurt?

• Equipment is sterilised.

• Milk is pasteurised (85-90°C) to kill unwanted bacteria

• Milk is cooled (40-45°C) and Lactobacillus added

• Milk incubated for hours while bacteria digest milk proteins and ferment the sugar (lactose) in the milk

• Bacteria converts lactose into lactic acid

  • increased acidity sours and thicken milk into yoghurt

  • lowered pH means yoghurt can be kept for longer

• Yoghurt stirred and cooled to 5°C to stop lactobacillus.

What is an industrial fermenter?

containers used to grow (culture) microorganisms in large amounts

Why and how are aseptic conditions controlled in industrial fermenters?

sterilised by hot steam

• to kill microorganisms

• prevent chemical contamination

Why and how are nutrients controlled in industrial fermenters?

needed for use in respiration

to release energy for growth

ensure microorganisms can reproduce

Why and how are optimum temperatures controlled in industrial fermenters?

monitored using probes

maintained using water jackets

• to ensure optimum temperature for enzymes

Why and how is the optimum pH controlled in industrial fermenters?

monitored by probe

adjusted by acids/alkalis

• to ensure optimum pH for enzymes

Why and how is oxygenation controlled in industrial fermenters?

oxygen is needed for aerobic respiration to take place

Why and how is distribution controlled in industrial fermenters?

agitation- stirring paddles ensure everything is evenly spread throughout the fermenter

What are the benefits of fish farming?

• doesn’t worsen overfishing impacts

• can be selectively bred

• can protect from predators

• can control water quality

• control feeding

• control conditions to ensure high yield

How is water quality maintained when fish farming?

water is filtered to remove waste + bacteria

cleaned to maintain high oxygen levels of aerobic respiration

How is intraspecific predation controlled when fish farming?

fish separated by age and size so they don’t eat each other

How is interspecific predation controlled when fish farming?

different species separated by fences, nets and tanks to prevent fighting

How are diseases controlled when fish farming?

antibiotics given to prevent disease

kept in small groups to minimise the spread

How is waste product removed when fish farming?

water is filtered to remove faeces/sewage

How is feeding frequency and quality maintained when fish farming?

food is high in nutrients for high growth

fed little but often to prevent overeating

How is selective breeding enabled when fish farming?

fish separated by sex so farmers can ensure only fish with desired characteristics can reproduce.