5.8 interpret and label a diagram of an industrial fermenter and explain the need to provide suitable conditions in the fermenter, including aseptic precautions, nutrients, optimum temperature and pH, oxygenation and agitation, for the growth of micro-organisms

Okay so to start, here is a diagram...

Conditions...

The fermenter must be kept aseptic so only the desired microorganism grows. In order to do this, it is cleansed (usually with steam) before production takes place.

Nutrients are provided to ensure that the microorganisms always have enough food to grow.

The optimum temperature and pH is maintained and monitored with probes (connected to a screen)  to ensure maximum growth. Also, if the temperature is too high, the enzymes will denature. An optimum temperature needs to be kept to ensure the best yield.

If the process requires aerobic respiration (not beer, for example, which requires anaerobic respiration of yeast to make ethanol), there is an oxygen supply.

Agitation/stirring takes place to ensure that the microorganisms, nutrients and temperature are evenly distributed.

image credit: BBC

5.7 undersand the role of bacteria (Lactobacillus) in the production of yoghurt

Lactobacillus is the bacteria that ferments milk (into yoghurt) in yoghurt production. This is the process...

- All equipment is sterilized in order to kill off any unwanted micro-organisms.

- the milk is heated to 72° for 15 seconds (pasturisation) in order to kill any germs in the milk.

- the milk is cooled

- The bacteria 'lactobacillus' is added.

- the mixture is incubated at around 40° in a fermenter. This is where the bacteria ferment the lactose sugar in the milk, forming lactic acid

- The lactic acid causes the milk to clot, causing it to solidify and turn into yogurt.

- Any flavourings/colourants are added

- the yogurt is packed

5.6 describe a simple experiment to investigate carbon dioxide production by yeast, in different conditions

When yeast respires aerobically, it produces carbon dioxide as a bi-product. Here is how to measure the effect of changing temperature on carbon dioxide production from yeast...

- mix together some suger, yeast aand distilled water. Add this mixture to a test tube

- attatch a bung with a delivery tube. Attatch the other end of the delivery tube to a test tube of water

- Put the tube containing the yeast/water/sugar solution in a water bath at 10°.

- leave to warm up for 5 minutes and then count how many bubbles are produced in one minute

- repeat with 4 other test tubes, one at 15°, one at 20°, one at 25° and one at 30°. You should also do one at room temperature as a control

- plot results in a graph and compare/find patterns/anomalies

should all go well, you should conclude that as temperature increases, the rate of respiration (and therefore amount of bubbles) should increase. However, if you have done a water bath past optimum temperature for the enzymes (as respiration is controlled by enzymes), then there will be very little/no data for this tube.

NOTE: You can use the same apparatus but measure the effect on different concentration of sugar, for example, by keeping the water bath the same temp but adding more/less sugar to each tube. the same can be done with volume of water and/or concentration of sugar solution etc

5.5 understand the role of yeast in the production of beer

When yeast respires anaerobically (without enough oxygen) it produces ethanol/alcohol as a bi-product. In beer production, yeast respires anaerobically. It is the ingredient in the production of beer that makes the alcohol, it ferments the sugars into alcohol.