Living Factories Biotechnology SG Biology
Jan 04, 2016
Living Factories
BiotechnologySG Biology
Learning Outcomes 1• State that the raising of dough and the
manufacture of beer and wine depend on the activities of yeast.
• Identify yeast as a single celled fungus, which can use sugar as food
• Using a word equation, state the process of fermentation of glucose by yeast.
• Describe the process of anaerobic respiration and compare it with aerobic respiration
Biotechnology• Biotechnology is the use of microbes
and raw materials to produce useful substances.
Biotechnology
Raw materials
Suitable micro-organisms
Biotechnological process
ServicesSewage treatment
Water purification
ProductsFood, enzymes
Fuels
Anti-biotics, hormones
Products of Biotechnology
Structure of Yeast
• Yeast is a single celled fungus
• It multiplies by budding
Yeast
• Yeast breaks down glucose into carbon dioxide and ethanol.– In bread making, the carbon dioxide
helps the bread to rise.– In brewing, the yeast turns sugars into
alcohol.
• Present on fruits, such as grapes as a bloom (grey dust).
Fermentation in Yeast
• Fermentation is respiration in the absence of oxygen (anaerobic respiration).
• It can be represented by an equation.
Glucose carbon dioxide + ethanol + energy
Stages in Bread making
• Add yeast to a warm sugar solution and allow to grow and produce bubbles.
• Add a pinch of salt to the flour• Mix together into a dough• Leave mixture in a warm place covered
by a cloth• Yeast releases CO2 bubbles making
dough rise• Bake dough in a hot oven• Yum Yum
Baking• Yeast is added to , and
.• is made which is folded and
left in a warm place.• (anaerobic respiration)
causes the yeast to produce ethanol and carbon dioxide.
• The causes the dough to rise.• The dough is then baked in the oven which kills
the yeast and removes the .• After baking the bread is ready.
Stages in wine making
• Crush grapes to release juice• Filter juice into fermentation tank• Add yeast to grape juice• Yeast grows using sugar and changes it
into alcohol (CO2 is allowed to escape)
• Alcohol becomes concentrated and kills the yeast
• Wine siphoned into bottles
Wine making• are crushed and the
grape juice is filtered off.• is added to the grape juice.• takes place, yeast uses the
sugar in the grape juice to make and .
• The is allowed to escape.• As the builds up it kills the
yeast.• The wine is removed into bottles and
allowed to .
Learning Outcomes 2
• Describe how commercial brewers provide the best growing conditions for yeast.
• Explain what is meant by the term “batch processing”
• Explain the need for malting of barley before use by the brewing industry.
Growing conditions for Yeast• Food supply– Starch is converted to sugar for yeast
by germinating barley grains on the floor of the malting house (malting)
• Suitable temperature– Optimum temperature maintained in
fermenter vessel by a thermostat• Lack of competition– Other microorganisms killed by
boiling in the wort kettle
Brewing
• A brewer is interested in both the alcohol and the carbon dioxide made by the yeast. – Beer is expected to be alcoholic– the carbon dioxide gives the
characteristic fizz.
Brewing
• Raw materials– Barley grains– Water– Extra sugar– Hops– Live yeast
• By products– Cattle food– Fertiliser– Yeast extract
Brewing (1)• Barely grains which are full of
, which is a large molecule that yeast can not digest
• Barley grains are allowed to germinate.– Starch is converted to sugar.
This is called .• Yeast is added and takes
place.
Brewing (2)• Yeast changes the maltose into
carbon dioxide and ethanol.• As the level builds up the
yeast is killed.• Beer is then made and allowed to
.• To brew the best beer the brewer
must make sure his fermenter vessels are _ and that he uses the
temperature for the yeast.
Learning Outcomes 3
• State that the manufacture of cheese and yoghurt depends on the activity of bacteria.
• State that the souring of milk is a fermentation process.
• Explain the souring of milk in terms of bacterial fermentation of lactose.
Fermentation of Lactose
• When the bacteria growing in milk respire anaerobically, they use the milk sugar lactose as food.
Lactose lactic acid
• This is called lactic acid fermentation
pH7
6
5
4
Days
1 2 3 4 5 6
Souring of milk
• Bacteria feeds on lactose producing lactic acid.
• Milk becomes more acid and its pH falls.
Cheese and yoghurt production
• Lactic acid makes milk curdle• Special strains of bacteria are used
in fermentation in curdling milk.
Flow diagram for the manufacture of yoghurt
Bulk raw milk pasteurisationcooler Incubation at
42oC for 6 – 8 hours
Chiller 5oC
PackagingCool
Storage4oC
Cheese and yoghurt• Cheese– Bacteria added– Milk curdles– Rennin (enzyme) used to
separate milk into curds and whey
– Whey run off– Curds cut into blocks
and mixed with salt to slow bacterial growth
– Packed into moulds
• Yoghurt– Bacteria
added to pasteurised milk
– Milk clots– Yoghurt
formed– Put into tubs
and stored in fridge