Biotechnology 2

Question 0

Outline the key events that led to the use of biotechnological practices including:

• yeast in the manufacture of bread
• yeast and fermentation for alcohol production
• the use of other micro-organisms for the manufacture of yoghurt and cheeses

Answer 0

Fermention: the breakdown of glucose and other simple sugars into CO2 and alcohol. For cheese and yoghurts, milk sugar is turned into lactic acid instead. Practicality-wise, fermentation is a way cells like yeast to gain energy without the need for oxygen. This is called glyocolysis which results in waste products such as ethyl alcohol, lactic acid or acetone (which can be used for fermentation).

Fermentation is essentially the allowance of microorganisms to chemically change a food product.

Mot biotechnological practices resulted by chance discovery and/or were drive by the need to store food for longer and out of their growing season.

YEAST FOR BREAD

• Been occurring for about 5000 years. It is thought that natural contaminants (e.g. wild yeast and lactobacillus) were added with milk. Dough samples were kept as starter samples to continue.
• Starch and sugar is added for the yeast to feed on, then moisture (milk, oil, water, butter) to activate yeast, warmth (25-40˚ C) and time. A process of proofing, punching, resting and kneading breaks apart the starch granules to release the protein gluten. This is denatured and elastified by the kneading and punching.
• Evidence of baked bread goes back to the Stone Age. The Bible and Ancient Egyptian artefacts refer to bread making.
• Until the 18th Century a left-over semi-solid from brewing beer, wine and vinegar was used as a yeast source. This produced bitter bread and had unreliable and small results. Modern bread is made from specialised yeast varieties.

YEAST/ FERMENTATION FOR ALCOHOL

• Wine making goes as far as Ancient Greek times. It naturally formed from fruit juices as yeast grew on the skin of the fruit. Beer was made from barley in ancient Egypt, also in Greece and Mesopotamia. Commercial production in Europe.
• Fermented drinks were used against a preventative against diarrhoea because it killed some pathogenic bacteria. Customs for alcohol were developed to prevent social breakdown.
• Archaeological evidence worldwide show alcohol production and storage: nectar drinks by Aus Aborigines, mead (honey), vodka (distilled potato), sake (rice), whiskey (grains), cider (apple) and wine (grapes)
• Pure and native yeast mixtures are used for modern alcohol production

OTHER MICRO-ORGANISMS FOR YOGHURT AND CHEESES

• Yoghurt and cheese are produced from lactic acid (product of anaerobic respiration). Lactic acid and rennin are used to produce modern cheese, with other microbial activity to diversify. For yoghurt, lactic acid breaks down the proteins into peptides.
• 10 000 BC rock drawings depict the milking of cows. Yoghurt was used in Europe and Asia.
• It is thought that the first cheese was accidentally created when a herdsman put milk in a sheep stomach carry bag. The milk changed into curds and whey by the rennin present. The curds were collected, pressed, then dried. Moulds would grow during the ripening process to give the cheese a distinct flavour.
• Yoghurt is a form of cheese.
• Modern cheese is produced with a bacteria that was genetically engineered to produce rennin (instead of calves).
• lactic acid fermentation produces dairy products such as yoghurt, buttermilk and cultured milk, using micro-organisms such as Lactobacillus bulgaricus and Streptococcus lactis.
• hard cheeses such as cheddar are produced from proteolysis and lipolysis which break down the products of proteins and lipids.
• Swiss cheese results from propiomic acid fermentation which uses Propionobacterium species
• Roquefort cheese (a blue cheese) is from lipolysis and the production of a blue mould pigment using Penicillium roqueforti.

Question 1

Plan, choose equipment or resources, perform a first-hand investigation to demonstrate the use of fermentation processes in bread or alcohol production.

Answer 1

AIM: To demonstrate the fermentation of yeast (anaerobic respiration) and the production of carbon dioxide.

MATERIALS:

• 1 conical flask w/ topper
• a delivery tube
• a jumbo test tube
• lime water
• dry yeast
• sugar
• a straw
• 100 mL warm water

RISK ANALYSIS:

• Broken glassware: handle with care and clean up immediately.
• Ingestion of limewater: use a bended straw.

METHOD:

Control: (check it will produce the result you want)

• add limewater to a small beaker until it is about a third full. Note the colour of the limewater.
• blow gently through a straw into the limewater.
• note any change to the limewater. You are looking for a precipitate. Consider it faulty if another reaction occurs.

Experimental Set Up:

1. Dissolve 5g of sugar in 100mL of lukewarm water in the conical flask.
2. Stir until the sugar dissolves.
3. The water should be 30-40C.
4. Mix in 1g of dry yeast by gently swirling the conical flask. Note that the yeast will not dissolve but instead stay suspended.
5. Add limewater to a test tube until it is about one third full.
6. Cover the conical flask with parafilm.
7. Place the end of the delivery tube from the side arm of the conical flask into the limewater in the test tube.
8. Leave the apparatus to stand in a tub of hot water.
9. Record any observations.

DISCUSSION:
Limewater (calcium hydroxide) reacts with carbon dioxide to produce the insoluble white salt, calcium carbonate. When something is insoluble in water, it floats around as particles and the clear solution changes to an opaque/cloudy suspension.

Equation:
GLUCOSE — CARBON DIOXIDE + ETHANOL
C6H12O6 — 2CO2 + 2C2H5OH

The appearance of the limewater gradually became cloudy when it came into contact with exhaled air.

The limewater turned cloudy in the experiment because it came into contact with a product of yeast fermentation: carbon dioxide.

Ethanol as another product of yeast fermentation was not identified.

Yeast is used in bread because the carbon dioxide produced forces the bread to rise.

RESULTS:

Limewater:
Control limewater alone - clear
Control lime water + exhaled air - cloudy

Initial appearance:
Yeast and sugar mixture - yellow
Limewater in test tube connected to fermentation apparatus - clear

Final appearance:
Yeast and sugar mixture - pale yellow
Limewater in test tube connected to fermentation apparatus - cloudy white

CONCLUSION:
The fermentation of yeast and the production of carbon dioxide was demonstrated using yeast, sugar and warm water — fermented to produce ethanol and carbon dioxide, proven by the observation of the limewater becoming cloudy.