MICROBES CAN MAKE USEFUL PRODUCTS

WJEC BiologyModule 3

You will learn:

• What products are made by microbes?

• What are the advantages of using microbes?

• How is commercial production carried out?

Learning outcomes

• To discuss the advantages of using microbes in food production.

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?

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.

Learning outcomes

• To understand how bacteria are used in yoghurt production

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.

Yoghurt production

• 5 stages – Pasteurisation

• 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.

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

Flow diagram for the manufacture of yoghurt

Bulk raw milk pasteurisationcooler Incubation at

42oC for 6 – 8 hours

Chiller 5oC

PackagingCool

Storage4oC

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?

Learning outcomes

• To understand how yeast is used in baking

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

Activation

• Yeast is activated by adding warm water and a little sugar

• Yeast respires aerobically and bubbles of carbon dioxide form

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

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.

Reactions in Proving

yeast enzymes

Sugar + water glucose + fructose

yeast enzymes

glucose + fructose alcohol + carbon dioxide

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

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.

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?

Watching Dough rise

• Online resource

Learning outcomes

• to investigate factors affecting fermentation in yeast

• to represent data collected in appropriate tabular and graphic form

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 anaerobicallySugar ethanol + carbon dioxide

• Anaerobic respiration produces less cellular energy than aerobic.

Factors affecting fermentation in yeast

• Sugar concentration• Temperature• pH• Type of yeast

Learning outcomes

• To discuss the commercial production of anti-biotics

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

Batch process in several stages

1. 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

2. When Penicillium has used up the nutrients it starts to produce penicillin as a secondary product.

• The temperature is changed for this stage

3. 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

4. Antibiotic is processed into a form where it is sold and used.

• All processes must take place under sterile conditions

• Temperature must be controlled throughout as penicillin can be easily damaged by heat.

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.

Learning outcomes

• To revise knowledge of enzyme action

• To understand the use of enzymes in food production.

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

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

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

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

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.

Pupil Activity

• Answer the exam question on pectinase

• Complete the activity worksheet analysing an experiment looking at the effect of temperature on pectinase action.

Learning outcomes

• to carry out at GCSE practical examination on the extraction of fruit juice using pectinase

Learning Outcomes

• To understand how biological washing powders help to remove stains

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

Biological washing powders

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

Biological powder advantages

• Improve stain removal• Reduce costs• Environmentally

– Biodegradable• Enzymes are proteins and break down

naturally in the environment

– Energy efficiency– Water efficiency

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?

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.