• Biotechnology means using microbes to make useful products.

• Microbes include bacteria and yeast- a fungus.

• Useful products include bread, beer, wine, human antibiotics, insulin, biological detergents.

• Biotechnology is a major growth industry in Biology.

Yeast

• Yeast is a single-celled fungus.

• It uses sugar as a food supply

•Yeast reproduces new cells in a process called budding

•Word equation

nucleus

cytoplasm

cell wall

buds

Sugar carbon dioxide + alcohol + energy

Respiration in YeastYeast respires glucose to obtain energy.

If oxygen is present it will carry out aerobic respiration, which releases most of the energy from the glucose.

If oxygen is not available it will continue to respire anaerobically, but in doing so receives much less energy.

Aerobic respirationglucose + oxygen lots of

energy+ carbon

dioxide+ water

Anaerobic respiration (fermentation)glucose a little

energy+ carbon

dioxide+ Alcohol

(ethanol)

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Fermentation Experiment

thermometer

layer of oil

vacuum flask

bicarbonate indicator

Yeast in boiled and cooled glucose solution

Boiling removes dissolved oxygen and kills all microbes. Cooling prevents yeast being killed when added.

Oil keeps oxygen out of yeast and sugar mixture.

Shows release of heat.

Prevents heat loss.

Detects release of carbon dioxide.

Control – the same as shown but use dead yeast

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ResultsAfter 2 days;

Experimental flask

Control flask

Thermometer reading

Rises from 20oC to 23oC

No change

Bicarbonate indicator colour

change

Orange to yellow

No change

Distillation of liquid in flask at 80oC

Ethanol collected

No ethanol

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Yeast is used in the baking and brewing industries.

Uses of Yeast

Respiration in yeast releases bubbles of carbon dioxide which spread through the dough, making it rise.

Yeast Ferments the sugars in fruit and grains to produce alcohol.

Alcoholic fermentationBrewers Yeast releases energy from sugar in the absence of oxygen (anaerobically) to produce alcohol

Brewing

The sugars required are obtained from barley grains during a process called malting.

Malting

Barley grains are soaked in water for 2 days.

The seeds germinate and the enzyme amylase changes starch into sugar.

Embryo produces amylase

Starch becomes sugar

embryo

Endosperm (starch store)

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Maltings BuildingCREDIT

Effect of germination on barley grains

dry barley grains contain starch but not simple sugar

barley grains that have been allowed to germinate for a few days contain simple sugar but only a little starch

germinating seeds need;

wateroxygen warmth

ConclusionStarch is broken down to simple sugar during germination

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starch simple sugar

amylase

this degradation process is brought about by an enzyme - amylase

normally in seed germination the sugar is used to provide food for the developing plant

in brewing the sugar is used to provide food for yeast for fermentation

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After malting;

1. The germinated barley grains are ground up with hot water to make a mash.

2. This is sprayed with hot water to retrieve the sugars.

3. The sugary liquid is boiled with hops in a wort kettle to give flavour and remove all unwanted microbes.

4. The resulting mixture (called wort) is cooled, yeast are then added and grown under ideal conditions in a fermenter.

5. The resulting beer is allowed to mature in casks.

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growing condition required by yeast

way in which growing condition is provided

food supplystarch converted to sugar for yeast by germinating barley grains on floor of malting house

suitable temperature temperature of fermenter vessel controlled by thermostat

lack of competitionall other micro-organisms killed by boiling in wort kettle before yeast is added

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FermentersA fermenter is a vessel which can be used to

manufacture a range of products in the presence or absence of oxygen.

They can be small and simple ….

… or large and complex – needing to be monitored by computer.

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Brewing -- Commercial Batch Processing CREDIT

Batch Processing This is the technique used by commercial brewers to

provide the best conditions for fermentation.

The common feature of all batch processes is that they involve closed systems.

After the addition of the raw materials, nutrients and yeast culture, the system is left untouched, although controlled, until fermentation ends.

The beer then has to be drawn off and separated from the yeast, and the fermenter system needs to be cleaned and sterilised before being re-used. This wastes time and money.

Fermentation ends because nutrients run out or waste materials build up.

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In brewing, the fermenter is a large copper tank into which are placed the nutrients and yeast

Sensors monitor the pH, temperature and oxygen concentration to provide ideal growing conditions for the yeast.( about 10oC – 18oC

and a pH of about 7)

(Respiration produces heat)

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ImmobilisationImmobilisation involves attaching a cell or enzyme to another substance so that it can’t move freely.

Whole cells such as yeast can be trapped inside gel beads.

Enzymes can be attached to glass beads.

enzymes enzymes attached to glass bead

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Free Yeast Immobilised Yeast

Many industries use immobilised cells or enzymes because;

• Products are separated easily and cheaply from cells or enzymes

• Products are easily purified.

• Less waste as cells / enzymes can be re-used

• Can be used in continuous flow processing

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Commercial Continuous Flow ProcessCREDIT

Continuous flow processing Raw materials continuously fed in

Product continuously removed

Enzyme (or cell) immobilised to glass / gel bead

Glass / gel bead

Fermenter vessel

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Continuous Flow Process;Can be expensive to develop and set up, but;

• Raw materials are continuously added to the fermenter, so the cells / enzymes receives a steady stream of raw materials.

• Product does not have to be separated from cells / enzymes, so money saved.

• Cells / enzymes can be used again, so money saved.

• Valuable time not lost in cleaning out and re-setting fermenter as in batch processing.

• Less waste and pollution as cells / enzymes not discarded.

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Fresh milk from a cow contains many bacteria

The bacteria multiply and make the milk go sour.

Lactose sugar in milk is broken down by bacteria to lactic acid

Milk is pasteurised before we can drink it to remove harmful bacteria.

Putting the milk in the fridge slows down the growth of any remaining bacteria.

The souring of milk by producing lactic acid is a “Fermentation process”

Bacteria

Lactose sugar Lactic Acid

Milk Fermentation by Bacteria

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Making yogurt• Yogurt relies on the souring

of milk by bacteria.• The milk is sterilised by

heating• Bacteria are added• The bacteria feed on the

milk sugar (lactose) and convert it to lactic acid , this makes the milk curdle and go lumpy and gives yoghurt its sour taste

• Flavourings and colourings are added to give the final product.

How Cheese is Made• Bacteria are added to

the milk to make it go sour.

• Next an enzyme called rennin is added.

• This breaks down the proteins in milk and causes the milk to separate into solids (curds) and a liquid (whey).

The liquid whey is then drained off.

The curd is finally allowed to ripen and mature to form cheese.

Some cheeses are then flavoured by adding different microbes.

Blue stilton