1. Uses of micro-organisms: Yeast and alcohol
S3 Biology
Uses of micro-organisms:
Yeast and alcohol

2. Recap - what are the two types of respiration?
- what is produced in yeast cells when they go through the 2 types of respiration? -

3. We are learning:
- to describe how yeast is involved in the brewing industry
- to describe the different types of beer and how they are produced

4. YEAST Single Celled fungus (plant)
No chlorophyll - cannot produce its own food.
Generally feeds on dead organic material.
Often seen as a grey dust on foods (like grapes and plums)
Needs food and a suitable temperature to grow
Multiplies by budding

5. Beer Yeast converts sugar into alcohol & CO2 This is fermentation
Fermenters are used for alcohol production
Beer is made from malt, water, sugar, hops & yeast
Alcohol content depends on:
- type of yeast used
- temperature of fermenter
- fermentation time
Yeast can be top or bottom fermenting

6. Beer maturing Beer is matured in a storage container
This develops flavour
Brewery conditioned beer
- stored in large tanks
- yeast removed, and extra CO2 added before packaging
E.g. lager
Cask-conditioned beer
- stored in wooden or steel casks
- yeast cells given more sugar, to produce more CO2
- beer often dark, with a strong flavour
E.g. ale, stout