Microorganisms and Industry Revision Notes PDF - Aberdeen Grammar School

Aberdeen Grammar School S2 Biology Topic 3 Microorganisms and Industry Revision Notes Name: _________________________________ Teacher: _________________________ 1  Topic 3 (part 1): The Growth of M...

Aberdeen Grammar School S2 Biology Topic 3 Microorganisms and Industry Revision Notes Name: _________________________________ Teacher: _________________________ 1  Topic 3 (part 1): The Growth of Microorganisms Learning intention  I have contributed to investigations into the different types of microorganisms and can explain how their growth can be controlled. Level Success criteria  I can name the three different types of microbes and describe their 3 features  I have grown different types of microbes on petri dishes using aseptic 3 techniques.  I have investigated the conditions that affect the growth of mould on 3 bread.  I can describe how conditions and chemicals can promote and restrict 3 growth, including temperature, antibiotics and antifungals. Topic 3 (part 2): Microorganisms & Industry Learning intention  I have taken part in practical activities which involve the use of enzymes and microorganisms to develop my understanding of their properties and their use in industries. Level Success criteria 4  I can describe the properties and industrial uses of yeast in brewing.  I can describe the properties and industrial uses of bacteria in yogurt 4 production. 4  I have investigated the properties of various enzymes used in industry.  I have investigated the use of enzymes in biological detergents and 4 stain removers. 2 Micro-organisms Micro-organisms are living organisms that are microscopic. They like all other living things require food, water, a suitable temperature and suitable pH to grow and multiply. Microbes will grow naturally on food sources like bread if they have all of these required conditions. We can provide microbes these requirements in a lab using a petri dish and a solid food medium called nutrient agar to incubate the microorganisms. There are three types of microorganisms: 1. Bacteria, 2. Fungi 3. Viruses Bacteria are single celled organisms of different shapes that can divide very quickly to produce new cells. Bacteria are found almost everywhere, some can be useful but some are harmful to humans and cause disease. Fungi are very varied in their shape. Some, like yeast, are oval and microscopic. Others such as bread mould, look like masses of microscopic threads. Some fungi can be very large as in the case of mushrooms! Some fungi can be helpful. Some produce/secrete a chemical called antibiotic that specifically kills bacteria. Yeast is used in brewing of alcoholic drinks and in baking breads. Some fungi however, can be harmful to humans as they cause diseases or can be poisonous to eat. Viruses are considered the smallest type of microbe, even smaller than bacteria. Viruses are really the bad guys of the microbe world. They cause diseases in animals and plants. 3 Controlling the Growth of Microorganisms The conditions microorganisms need to grow: a food supply, water, suitable temperature and pH, can all be used to control their growth. 1. If the temperature is too high or too low they cannot grow. This is why boiling and freezing food can help stop microorganisms from spoiling it. 2. If conditions are too dry microorganisms also struggle to grow, this is why dried foods keep very well. 3. Adding dehydrating chemicals like salt and sugar also prevents growth, along with changing the pH by adding acidic vinegar. 4. Antiseptic wipes and disinfectants contain chemicals that kill bacteria and fungi. 5. Antifungal agents can help clear up fungal infections like athletes’ foot or toe nail fungus. 6. Antibiotics kill all bacteria only and hence bacterial infections alone can be cleared using antibiotics. Antibiotics Antibiotic drugs help treat and cure bacterial infections. An antibiotic called Penicillin, is made by a fungus and was discovered by Alexander Fleming in 1928. Other antibiotics have since been discovered and there is a wide range available depending on what bacteria is present. Testing the efficacy of antibiotics in killing bacteria Antibiotic drugs can be tested in labs to see which ones will be most effective in killing bacteria. Antibiotic discs are placed on petri dishes of bacteria to see how much growth is prevented. Clear areas around the disc indicate no bacterial growth. Doctors would pick the best antibiotic to treat the bacterial infection. 4 Cheese & Yoghurt Making Fresh milk from a cow normally contains many bacteria. During the souring of milk, the bacteria feed on the sugar in milk called lactose and break it down using enzymes into lactic acid. Lactose Lactic Acid The manufacture of cheese and yoghurt depend on the curdling of milk. Lactic acid is needed to make the milk curdle. It is produced during fermentation by special strains of Bacteria added to the milk for this purpose. Yoghurt Making 1. Milk is heated to 73°C for at least 30 seconds to make it virtually sterile. 2. ‘Sterilised’ milk cooled to 44°C. 3. Special ‘yoghurt’ bacteria added to sterilised milk. 4. Milk kept at 44°C for 4 hours to allow bacteria to convert it to yoghurt by making lactic acid. 5. Yoghurt stored in cartons at 4°C to slow down further bacterial action. Cheese Making There are several steps in the manufacture of cheese; the milk is pasteurised to kill most of the bacteria special bacteria are added to convert the milk sugar into lactic acid enzymes (rennet) are added to clot the proteins in milk. This forms the curds and whey  The milk clotting enzymes (rennet), which were used originally, always came from animals such as calves. Nowadays the enzymes used in cheese making can come from a variety of different sources: a. rennet from calves. b. an enzyme which is similar to rennet but which is made by a fungus. c. an enzyme which is produced by yeast which have been genetically modified to produce rennet. 5 Yeast Yeast is a single celled fungus. It uses glucose as a food source. Carbon dioxide and alcohol are waste products.  It is used in bread making to make the dough rise due to the CO2 bubbles released.  It is used in the production of alcohol. As yeast grows it uses the sugar for energy and changes into alcohol. Other Uses of Enzymes in Industry: Uses of enzymes enzyme use protease used to pre-digest proteins during the manufacture of baby foods lipase used - together with protease - in biological detergents to break down - digest - the substances in stains into smaller, water soluble substances carbohydrase used to convert starch syrup, which is relatively cheap, into sugar syrup, which is more valuable - for example, as an ingredient in sports drinks isomerase used to convert glucose syrup into fructose syrup - fructose is sweeter than glucose, so it can be used in smaller amounts in slimming foods The next two pages detail the uses of yeast in industrial processes and the production of cheese and yogurt. 6 7 8 Washing Powders  The word detergent means “something which cleans”. So it includes soaps, washing up liquid and washing powder. Biological washing powders contain enzymes and are added to the washing powder because they improve the way in which it cleans. In a biological washing powder only about 1% of the powder is enzymes. The enzymes mean that you can wash clothes with biological powders at a lower temperature than with non-biological and this saves energy. 9