biotechnology

Biotechnology

Living Factories

G Davidson

April 22, 2023 G Davidson 2

Yeast at Work• Yeast is a tiny living thing.• It is called a microbe.• It is used in baking and brewing.


Yeast at Work• Yeast makes many useful products.• E.g. yeast can break down glucose

into carbon dioxide and ethanol (alcohol).

• This is called fermentation.• Yeast obtains energy by doing this.


Yeast Cells


Simple Fermenters• A fermenter is a vessel which can

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

• Yeast can be used to ferment sugars to produce many useful substances for man.


Simple Fermenter


Large Fermenters


Brewing• Wild yeasts are to be found on most

fruits, seeds and flowers.• Long ago people found that when

they stored fruits, seeds and flowers in water, new liquids were made.

• These were called wine and beer.


Brewing• The wild yeasts were responsible for

this.• Today, only particular strains of yeast

are used in brewing and wine-making.• To make beer which can be sold to

the public, commercial brewers must give the yeast the best growing conditions.


Taking Care of Yeast• Living yeast is used in fermentation.

• It usually works best at temperatures between 10oC – 18oC and a pH of about 7.


Taking Care of Yeast• Given these conditions, a controlled

supply of oxygen and sugar as food, yeast will grow well.

• It is also important that unwanted microbes are kept out.


Starch & Germination• Starch is present in barley grains.• This starch cannot be used by yeast

as a food.• First of all brewers must germinate

the barley.• Barley grains contain enzymes.• Germination allows the enzymes in

the barley to act on the starch.


How Yoghurt is Made


How Yoghurt is Made• Milk can be changed into cheese and

yoghurt.• This preserves milk.• People have done this for hundreds

of years.


How Yoghurt is Made• Certain bacteria are used in this

process.• Two strains of bacteria are used to

make yoghurt.• They ferment the milk sugar (lactose)

into lactic acid.• This acid makes the milk curdle and go

lumpy and gives yoghurt its sour taste.


Cheese Making


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 forms the solid curd.


How Cheese is Made• 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.


Cheese Making


Souring of Milk• Bacteria and sugar are present in

fresh milk.• The bacteria can feed on the sugar

and cause milk to sour.• The souring of milk is a fermentation

process.


Malting• Nowadays the brewing of beer, which

involves malting and batch processing, is carefully controlled using modern scientific methods.

• Malting changes the starch in barley into sugars which can be fermented by yeast.

• The whole process takes 7-8 days and is carried out in the maltings building.


Malting• First the barley is soaked; this is

called steeping.• Extra water is then removed and the

grain is turned regularly to allow aeration.


Malting• At this stage the temperature is

carefully controlled to regulate germination of the grain.

• When germination begins, enzymes in the grain break down the starch into maltose.

• During the brewing process the maltose is converted into fermentable sugars.


Maltings Building


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.


Batch Processing• The beer is then removed.• Fermentation ends because nutrients run

out or waste materials build up.• The growth rate of the yeast is therefore

higher at the start, falling to zero at the end.

• Batch processing which is monitored and controlled to give optimum conditions maximises the quality and quantity of the beer.

biotechnology

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