Microorganisms and their application

• Water Jacket- to control the temperature of the penicillium
• Acid/ Alkali reservoir- to control the pH
• Sterile air in and air diffuser- to maintain aerobic conditions for the fungus by bubbling the air through the culture
• Inoculated agar plates are incubated at 25 degrees in school for 24-48 hours. This encourages growth of the culture and ensures no human pathogens are produced.
• An inoculating loop is used to transfer bacteria and is sterilised before and after use by heating it to red heat with a Bunsen flame. It is allowed to cool before use, so it does not kill the bacteria.
• Only lift the Petri dish lid slightly as this prevents microorganisms from the air contaminating the culture. The lid is sealed with tape to prevent accidental removal. The tape is labelled and dated.
• In the production of penicillin, a starter culture of the fungus Penicillium is added to a liquid nutrient culture medium in a fermenter. In a fermenter, the supply of air, the temperature and pH can be controlled to enable maximum growth to take place. The organism grows and secretes the antibiotic into the surrounding medium. After incubation, the culture medium is filtered and the penicillin extracted.
• Refrigeration slows bacterial growth and freezing stops bacterial growth.
• One bacterium will give rise to one colony. However, inaccuracies in counting can be caused by the clumping of bacteria.
• The Petri dishes and nutrient agar must be sterilised before the agar is poured onto the dishes. This could be done using an autoclave, or by heating to a high temperature. This is to kill any unwanted microorganisms.
• Work is carried out near a lit Bunsen burner- hot air rises so microorganisms in the air should be drawn away from the culture.
• Test for antibiotics- Use sterile forceps (flamed forceps) to place paper discs soaked in different types or different concentrations of antibiotics on an agar plate with an even covering of bacteria.
• Agar plate- A petri dish containing nutrient agar which is a jelly containing all the nutrients that the microorganisms need.
• Penicillium needs oxygen for respiration. This is added by pumping in sterile air. This increases the product yield because the fungus can respire to provide energy for growth.
• The temperature is kept at an optimum level. A water-cooled jacket makes sure it does not get so hot that the enzymes denature.
• The pH is kept at an optimum level for the fungus' enzymes to work efficiently. This keeps the rate of reaction and product yield as high as possible.
• Refrigerating food slows growth as it slows the rate of enzyme-controlled reactions. The food still decays but the rate of decay is slower than if the food was left at room temperature.
• Freezing food stops bacteria from growing, allowing food to be preserved for months. However, the bacteria aren't killed and will start growing again once the food is defrosted.