1. MICROBES CAN MAKE USEFUL PRODUCTS
WJEC Biology
Module 3

2. You will learn: What products are made by microbes?
What are the advantages of using microbes?
How is commercial production carried out?

3. Learning outcomes
To discuss the advantages of using microbes in food production.

4. Time to Think how do we make use of microbes in food production?
gives examples of microbes used
can you think of any advantages in using micro-organisms in food production?

5. Microbes in Food production
Advantages of using microbes in food production
rapid growth
contained growth so minimum space is used
predictable product is made under controlled conditions
they may grow on waste materials from other processes.

6. Learning outcomes
To understand how bacteria are used in yoghurt production

7. Yoghurt Production
Yoghurt is a thickened milk product with a sour taste
The sour taste is produced by bacteria introduced into the milk which breakdown lactose (milk sugar) to lactic acid.
The low pH of lactic acid prevents other microbes from growing in the milk.
Yoghurt production is a batch process.

8. Yoghurt production 5 stages Pasteurisation Cooling Incubation Chilling
Raw milk is pasteurised by heating the milk to 93oC, this kills unwanted bacteria
Cooling
Incubation
Bacterial culture is added to the cooled milk
Chilling
Temperature reduced to 5oC, reducing bacterial enzyme activity
Packaging
Into sterile yoghurt pots, which are sealed and stored below 4oC.

9. Incubation
Streptococcus thermophilus and Lactobacillus bulgaricus bacteria convert milk sugar (lactose) into lactic acid
Optimum temperature 42oC
The lactic acid produced lowers the pH
Milk protein coagulates (thickens)
Process takes 4 – 6 hours

10. Flow diagram for the manufacture of yoghurt
Incubation at
42oC for
6 – 8 hours
cooler
Bulk raw milk
pasteurisation
Cool
Storage
4oC
Chiller 5oC
Packaging

11. Quick Questions on Yoghurt production
At what temperature is the raw milk pasteurised for yoghurt manufacture?
If pasteurisation were not carried out, what could happen to the yoghurt?
Write a word equation for the chemical reaction that causes the pH of yoghurt to drop.
Why should you remember Pasteur when you drink milk or eat yoghurt?

12. Learning outcomes
To understand how yeast is used in baking

13. Yeast in Bread Making
“strong flour” (flour with a high gluten content) is used as this provides a more stable loaf with even air pockets.
Stages in bread production
Activation
Kneading
Proving
Leavening
Baking

14. Activation Yeast is activated by adding warm water and a little sugar
Yeast respires aerobically and bubbles of carbon dioxide form

15. Kneading Activated yeast is added to “strong flour” to make dough.
Dough is kneaded to
distribute yeast evenly through the dough
Remove most of the carbon dioxide

16. Proving Dough is put in a warm place
Yeast respires anaerobically and different enzymes in the yeast speed up the breakdown of sugars to form alcohol and carbon dioxide
CO2 causes the volume to increase.

17. Reactions in Proving yeast enzymes Sugar + water glucose + fructose
glucose + fructose alcohol + carbon dioxide

18. Leavening Dough is kneaded for a second time
Carbon dioxide produced is trapped in the dough in small bubbles
When the bubbles expand the volume of the dough is increased.
This gives the bread its light texture

19. Baking
When the dough has doubled in volume again, it is baked in a hot oven.
The high temperature denatures the yeast enzymes stopping further reactions.
Alcohol evaporates and the carbon dioxide bubbles expand.

20. Baking Questions What is the source of enzymes for bread making?
If a thermostat failure caused the proving temperature to rise to 65oC in a bakery, would you expect to get “super-sized” loaves? Explain your answer.
What is the role of gluten protein in the bread-making process?

21. Watching Dough rise
Online resource

22. Learning outcomes
to investigate factors affecting fermentation in yeast
to represent data collected in appropriate tabular and graphic form

23. Fermentation in Yeast Yeast is a single-celled fungus
Is reproduces asexually by budding
Yeast can respire aerobically
Sugar + Oxygen  carbon dioxide + water
Yeast can also respire anaerobically
Sugar  ethanol + carbon dioxide
Anaerobic respiration produces less cellular energy than aerobic.

24. Factors affecting fermentation in yeast
Sugar concentration
Temperature pH
Type of yeast

25. Learning outcomes
To discuss the commercial production of anti-biotics

26. Antibiotic Production
Penicillin is a widely used anti-biotic, first discovered by Alexander Fleming in 1928.
Large-scale production of penicillin requires
sterile conditions
Fermenter
Nutrient medium
Aeration with sterile air

27. Batch process in several stages
A sterile sample of Penicillium is added to the culture medium
The sterile culture medium contains the substances necessary for rapid growth of the mould
Lactose
Amino acids
Mineral ions
Vitamins
pH and temperature are set at optimum levels

28. When Penicillium has used up the nutrients it starts to produce penicillin as a secondary product.
The temperature is changed for this stage

29. After about a week, the maximum antibiotic concentration is reached
Mould is filtered from the fermentation liquid
Antibiotic is separated from the liquid, purified and crystalised
Antibiotic is processed into a form where it is sold and used.

30. All processes must take place under sterile conditions
Temperature must be controlled throughout as penicillin can be easily damaged by heat.

31. Fermenter
A fermenter is a large steel vessel used for biochemical reactions.
Sensors monitor the conditions inside
The sensors send information to a computer, which then controls input valves to maintain temperature, pH, nutrient and oxygen levels at the optimum value.

33. Learning outcomes To revise knowledge of enzyme action
To understand the use of enzymes in food production.

34. Industrial productions and the use of enzymes
Industrial application of enzymes includes
Food, wine and beer production
Making fructose sweeteners for soft drinks
Laundry detergents
Producing “stone washed” jeans
Manufacturing pharmaceuticals

35. Enzymes
Enzymes are used in industry as they bring about reactions at normal temperatures and pressures which would otherwise require expensive, energy demanding equipment
All enzyme reactions also give a pure and reliable product.
To produce enzymes, micro organisms are cultured in a fermentation process

36. Enzymes in food production
Early uses of enzymes in the food industry include the production of sweet syrups by breaking down starch.
Carbohydrase and isomerase enzymes are commonly used

37. Uses of enzymes in food production
Baby food
Some baby food is pre-digested using proteases so that the baby can use amino acids without digestion
Baby-milk powders are manufactured from cows’ milk and are treated with enzymes to break down the proteins
This reduces the risk of allergic reactions

38. Fruit Juice production
pectinases are used for extracting fruit juice.
Pectin in fruit holds the cellulose fibres in the cell wall together
The enzyme pectinase breaks down the pectin and cell walls releasing the juice.

39. Pupil Activity Answer the exam question on pectinase
Complete the activity worksheet analysing an experiment looking at the effect of temperature on pectinase action.

40. Learning outcomes
to carry out at GCSE practical examination on the extraction of fruit juice using pectinase

41. Learning Outcomes
To understand how biological washing powders help to remove stains

42. Biological Washing Powders
Modern biological washing powders use enzymes that function efficiently at low temperatures, this reduces fuel costs.
Food or biological stains include
Fats and oils from fried items, butter or oily dressings
Protein from eggs, grass or blood
Starches from sauces made with flour

43. Biological washing powders
Biological washing powders have the following enzymes added
Lipase to breakdown fats
Proteases to digest proteins
Carbohydrases to remove starch stains

44. Biological powder advantages
Improve stain removal
Reduce costs
Environmentally
Biodegradable
Enzymes are proteins and break down naturally in the environment
Energy efficiency
Water efficiency

45. Pupil Activity
The instructions on the box state that biological washing powders are not effective when used at temperatures above 40oC
Explain why this is so.
If you had dropped fruit and cream down the front of your best silk shirt, what would be the advantage of using biological washing powder?

46. Pupil Activity
In the table write in whether you think the benefits are for the
Customer
Environment
Read through the handout and answer the questions on Stone washed jeans.