Biology B3 Higher Tier (Topic 3) Microbiology.

Final Topic :)

Info taken from AQA Revision guide.

(some stuff taken from 'Beer, Wine, Yogurt and Cheese Making' by nom.)

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  • Created by: Lawraa
  • Created on: 19-05-09 19:49

Growing microbes.

Microorganisms are grown on Perti dishes in agar (culture medium).

Agar contains:

- carbohydrate (energy source)

- supplementry nutrients (proteins, vitatmins, minerals)

Instruments used like culture medium, Petri dish and inoculating loop need to be sterilised.

In schools, culture is incubated at 25 degrees C as higher temperatures can cause harmful pathogens to grow.

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Food production using yeast.

Yeast is a single-celled organism with a nucleus, cytoplasm, cell membrane and a cell wall.

When O2 is present they respire aerobically and reproduce quickly.

However, when O2 is not present they respire anaerobically and produce ethanol and CO2 . This is called fermentation.

Making beer from yeast:

- starch in barley grains is used as the carbohydrate energy source

- starch is broken down into sugars in the barley grains by enzymes during the germinating process

- when there sugars have been fermented hops are added to give flavour

- beer is pasturised before sold to kill microbes

Making wine from yeast:

- fruit is crushed this gets juice and sugars out of it

- not always necessary to add yeast (there's natural yeast in fruit), yeast is needed as an energy source

- after fermentation the wine is cleared, stabilised and matured

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Food production using bacteria.

Bacteria are used in the manufacture of cheese and yogurt.

Making yogurt:

- bacteria are added to warmed milk

- milk sugar (lactose) is fermented by the bacteria, producing lactic acid

- lactic acid causes milk to solidify and yogurt is formed

Making cheese:

- milk protein turns solids to curds

- milk protein is preserved as cheese

- curds get more acidic which encourages solidification

- curds are separated from the liquid by filtration

- curd is made into hard cheese by filtering it, flavouring it and pressing it.

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Large-scale microbe production.

Microorganisms cna be grown on a large scale in an industrial ferementer.

Fermenters are carfully monitored:

- O2 is provided for respiration

- a stirrer is used to keep microorganisms spead out and ensure a constant temperature throughout the vessel

- a water-cooled jacket also helps maintain a constant temperature are microorganisms release heat

- sensors to monitor pH and temperature

A mycoprotein can be produced using the fungus, Fusarium (which is grown aerobically on starch)

Mycoprotein is a protein-rich food for veggies.

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Antibiotic production.

Antibiotics are produced in fermenters.

Penicillin is made from the mould Penicillium but only when most of the nutrients are used up.

The culture medium contains:

- sugar (for energy)

- other nutrients, including nitrogen

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Biogas (fuel for energy) is mainly methane from plants and waste products (CO2) which are broken down anaerobiocally.

It can be made on a large scale with wast from sugar factories or sewage works.

It can be used on a small scale at home or on a farm.

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More biofuels.

Sugar cane juices and glucose (derived form maize starch by the action of a carbohydrase enzyme) can be fermented to produce ethanol.

The ethanol produced (from the anaerobic respiration of microorganisms) can be distilled and used as a fuel.

Using ethanol could replace fossil fuels in the future.

Ethanol is more 'carbon friendly' so better for the environment.

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