BiotechnologyA Living factories

Yeast is a microscopic single-celled fungus. It is found naturally on many types of fruit such as grapes.Yeast is now used to make many useful products. Its usefulness stems from its ability to use glucose as a source of energy. It does this in a process called fermentation.

The word equation for fermentation is

yeastglucose energy + carbon dioxide + ethanol

Anaerobic respiration

You may have noticed that the fermentation equation is fairly similar to another equation you have come across, namely, aerobic respiration.Compare the two equations

yeastglucose energy + carbon dioxide + ethanol

glucose +oxygen energy + carbon dioxide +water

Both of these two types of process can be performed by yeast. When oxygen is available, yeast performs aerobic respiration. When oxygen is not available yeast performs anaerobic respiration (fermentation).

The table below compares the two type of respiration:

Aerobic respiration Anaerobic respirationOxygen required No oxygen requiredNo energy left on products Ethanol still contains energyRelease a lot of energy Release some energy

Yeast at work in baking

Two beakers are set up as follows and left until the following day:

A B

Yeast, flour flour && glucose glucose

The results were as follows:

A B

ConclusionWhen yeast ferments, it makes two important products, ethanol and carbon dioxide. In baking the carbon dioxide bubbles make the dough rise. The ethanol is burned off during the baking process.

Yeast at work in brewing

We have seen that when yeast is deprived of oxygen, it produces carbon dioxide and ethanol. The following equipment can demonstrate this:

ResultsThe temperature rose from 22oC to 29oC.The bicarbonate indicator changed from red to yellow, showing carbon dioxide had been made.Ethanol could be smelled.

ConclusionFermentation has occurred.

Commercial brewingIn beer making, fermentation is carried out on a larger scale using fermenters.To make beer that can be sold to the public, commercial brewers must give the yeast the best growing conditions:

1. a food supply – starch in barley grains is converted to maltose I a process called malting

2. a suitable temperature – a thermostat ensures that a constant temperature is maintained

3. no competition – all microorganisms except yeast are killed off to prevent competition and possibly contamination.

The malting of barleyBarley contains starch. This starch cannot be used by yeast as a food so the brewers must first germinate the barley grains. Enzymes in the grains then convert the starch to the sugar maltose that the yeast can then use.Modern brewing involves malting and batch processing.

Bat ch processing This is the technique used by commercial brewers to provide the best conditions for fermentation.

All the raw materials are added at the start.The system is left untouched until fermentation ends.The process is monitored and controlled to ensure that optimum conditions of temperature etc are maintained. When the process of fermentation is finished the products can be removed. The fermenter is then cleaned and sterilised ready for the next batch of beer.

The souring of milkBacteria and a sugar, lactose, are present in fresh milk. The bacteria feed on the sugar and cause the milk to sour. The souring of milk is a fermentation process.

bacterialactose lactic acid

Samples of milk of various ages were tested with pH paper:

Age of milk

pH number

1 72 6.53 54 4.55 3

ConclusionThe pH of milk decreases as the milk gets older. Lactose is sugar in milk. The souring of milk is brought about by fermentation carried out by bacteria. The lactose sugar is converted to lactic acid.

How yoghurt and cheese are madeCheese and yoghurt are made by curdling milk. Lactic acid is needed to curdle the milk.Manufacturers add certain strains of bacteria to the milk. Different types of bacteria give the different types of cheese and yoghurt.

B Problems and profit with wasteProblems with untreated sewageSewage is mostly organic waste and is produced in large amounts by humans. To avoid disease, it must be dealt with safely and quickly.

Untreated sewage decreases the pH and the oxygen content of the river water.

Sewage and healthIn the first half of the 19th century, untreated sewage was dumped into the rivers that were then used as drinking water and for washing. This often resulted in disease and death. Even in modern Britain, a natural disaster like flooding could disrupt the sewage treatment systems and the threat of such disease could return. Some diseases that could be spread by untreated sewage or a failure to wash hands after a visit to the toilet are

Typhoid Diphtheria Polio

Cholera Food Poisoning

Sewage treatmentThe main process in the treatment of sewage is its breakdown by the action of micro organisms to products harmless to the environment.Oxygen is required by the micro organisms and this is usually provided at the treatment works by using compressed air.The complete breakdown of sewage is only possible under aerobic conditions. Under anaerobic conditions, sewage is only partly broken down leaving some harmful products. If these products were released into the river they would provide food for other bacteria that would then use up the oxygen in the water.

Sewage is a mixture of many organic compounds. Each species of micro organisms can only break down a few substances and therefore a range of different micro organisms are required to completely remove all sewage materials.

Worki ng with micro organisms Microbes can help in the manufacture of food and drink, treating sewage and can cause disease.Many microbes are always present in the air, in all surfaces and inside open containers so precautions must be taken to prevent unwanted microbes growing (contamination).Therefore when working with micro organisms in the laboratory, it is important to adopt a safe practice.

1. Petri dishes of agar jelly must be kept closed until ready for use so that no unwanted microbes can contaminate the agar.

2. Hands must be washed before and after experiments so that no bacteria are transferred into or outside the laboratory.

3. Petri dishes are sealed after being inoculated so that no bacteria are accidentally spilled.

4. After use, petri dishes are first sterilised in an autoclave and then disposed of safely. An autoclave heats the dishes to a very high temperature to kill all bacteria.

ContaminationContamination is the presence of unwanted, perhaps harmful, micro organisms. Beer production is one area where contamination may occur.In between batches, manufacturers sterilise all their equipment and then check to make sure each it is indeed sterile.Particular care has to be taken to remove unwanted fungal and bacterial spores. This is done by 1. regular checks for contamination.2. the use of high temperature steam.3. chemicals such as caustic soda.

Microbes and decayWhen an organism dies, its tissues decay, mainly due to the action of certain micro organisms. The micro organisms use the dead tissue as a source of energy. These micro organisms are also known as decomposers.

Microbes and recyclingRecycling is not new. Nature has been recycling or millions of years. To keep an ecosystem in balance materials must be recycled. The two main cycles are the carbon and the nitrogen cycles.

Carbon cycle

CO2 is added to the atmosphere by respirationCO2 is removed from the atmosphere by photosynthesis. Bacteria feed on dead remains and faeces and release CO2 back into the air during respiration.

Nitrogen cycle

Bacteria are involved in many stages of the nitrogen cycle:Nitrogen-fixing bacteria (4) – plants such as peas and beans have nodules on their roots that contain these bacteria. The bacteria convert nitrogen from the air into nitrate and thus such plants have their own ‘fertiliser factory’ with them.

Nitrifying bacteria (2) – they convert ammonium compounds to nitrite and then to nitrate

Denitrifying bacteria (3) – remove nitrogen compounds from the soil and put nitrogen back into the air

Fuels from fermentationThere are advantages to using fermentation fuels rather than fossil fuels.Fermentation fuels – methane, ethanol, biogasFossil fuels – coal, oil and gas

Fermentation fuels Fossil fuelsHarmless to the environment Harmful to the environment

Easy to obtain Difficult to obtainCheap to obtain Expensive to obtain

Renewable Non-renewable

Upgrading wasteUpgrading waste is a means of obtaining useful products from unwanted waste material that would otherwise have to be disposed of and. might harm the environment. Microorganisms are used to

change the waste into substances which can be used as an energy source or high quality protein food.

Example 1 BiogasThis can be made by the decomposition of farm yard manure and household rubbish by microbes. The biogas can then be burned as a source of energy.

Example 2 WheyWhey is the waste liquid from cheese making. Whey can be used as a component of cattle feed or in biscuits and cakes.

Example 3 Fruit pulpFruit pulp is the waste from making fruit juices.Manufacturers now add the enzyme pectinase to the waste fruit pulp. Pectinase breaks down the pectin in the plant cell walls releasing more juice.

Sin gle cell protein Most microorganisms can reproduce much faster than plant and animal cells can by asexual reproduction where the cell simply divides in two.

1 cell

2 cells

4 cells and so on

By this method these cells can increase in number in a matter of hours and make them ideal for growing food etc.

Single cell protein - some kinds of yeast produce a rich supply of oil. In the future it is hoped that this yeast can be grown to supply a source of human food.

Mycoprotein – some fungi produce mycoprotein which is thread-like. This can be used to mimic meat and provides a vegetarian source of protein. It is at present sold under the brand name Quorn.

C Reprogramming MicrobesBacteriaBacteria cells are much smaller than animal cells.Both bacterial cells and animal cells have a nucleus but some bacterial cells have extra chromosome material called plasmids which can be transferred from one bacterial cell to another. Just like other cells, the normal control of the bacterial cell’s activities depend on its chromosome material.

Genetic engineering Genetic engineering is very important to biotechnology. It enables us to direct microbes to make products they would not normally make eg human genes can be placed into microbes to make substances useful to humans.

Pieces of chromosome can be transferred from a human cell into a bacterial cell and allow the bacteria to make a new substance.

First the chromosome material is removed from a human cell. One gene is removed. The plasmid is carefully removed from a bacterial cell and the ring is opened. The human gene is inserted into the plasmid. Lastly the altered plasmid is placed back into the bacterial cell.The bacterial cells multiply and produce large quantities of whatever protein the gene was the instruction for. This protein is now produced more quickly with less expense.

Useful products of genetic engineering

Insulin - this hormone is produced by the pancreas and regulates the amount of sugar in the blood. People who cannot produce this hormone sufficiently suffer from diabetes. More people are living longer and the number of people being diagnosed with diabetes is

increasing. Thus the demand for insulin has risen sharply. Before biotechnology the insulin was obtained from pig pancreases. Many people were allergic to the pig insulin. Now human insulin can be mass produced using genetic engineering and bacteria.

Growth hormone – Many children if diagnose early enough can benefit from doses of human growth hormone so the reach a more average height.

Genetic engineering versus selective breeding

Both of the above methods can alter the genotype of species that are useful to man.

Selective breeding Genetic engineeringYears of careful selection of required characteristics

Alters the characteristic immediately

Breeding over many generations Immediately new species

Improves an already present characteristic

Species has a completely new characteristic

Biological detergentsSome detergents are called biological detergents. This means that they contain enzymes such as proteases and lipases that will breakdown stains like egg, milk or blood. These enzymes have been extracted form soil bacteria.

The use of enzymes in such detergents have meant that washing clothes can now be done at much lower temperatures, saving time and energy. It also allows delicate fabrics to be cleaned better with less damage to the fabrics.

AntibioticsIn 1928 a Scotsman called Alexander Fleming discovered that a substance made by a fungus prevented the growth of bacteria. This substance was penicillin and was the first known antibiotic. Since then many other antibiotics have been discovered and used against diseases caused by bacteria.

A range of antibiotics is required because no one antibiotic is effective against all bacterial diseases as the following experiment shows. A multidisc has different antibiotics on each “spoke”

G, C, TE and S all can combat this bacteria but antibiotics P and E are ineffective.

Immobilising enzymesIn most enzyme reactions the following takes place:

{substrate + enzyme} mixture {product + enzyme} mixture

Separating the enzymes from the products can be expensive for some industries and sometimes the enzyme cannot be reused.A new technique called immobilisation has saved industries a lot of time and money because it allows the enzyme to be reused again and again and the products are easily separated from the mixture.

This is achieved by trapping the enzymes or yeast cells in jelly, immobilising them:

Continuous flow processingIn some industries, continuous flow processing is more efficient and cost effective than batch processing.

1. The enzyme does not have to be separated from the enzyme

2. The expensive enzyme can be reused.3. Valuable time is not lost during change over of batches.4. The problem of waste disposal is reduced as possibly harmful

substances are not released into the environment because the enzymes are not thrown away.