Industrial fermentation processes begin with suitable microorganisms and specified conditions; e.g., careful adjustment of nutrient concentration. There are many products of yeast fermentation such as alcohol, glycerol, and carbon dioxide.
In industrial fermentation microbes like yeast and bacteria can be used to make useful chemicals on a large scale. The fermenter is filled with nutrients and a small amount of a microbe, such as yeast. It is important to make sure that the microbe has the best possible conditions for growth. These include:
- Sterile conditions. The fermenter vessel is made out of stainless steel. Super-heated steam is pumped through it to kill any unwanted microbes.
- Oxygen. Some types of microbes need oxygen to grow. Sterile air is bubbled in from the bottom of the fermenter. Motorised paddles make sure the oxygen is mixed in.
- Heat. The reactions inside the generator release a lot of heat. Too much heat would kill the microbes. Water circulates in a cooling jacket to lower the temperature.
The process of alcoholic fermentation requires careful control for the production of high quality wines. Requirements include suppression of the growth of undesirable microorganisms, the presence of adequate numbers of desirable yeasts, proper nutrition for yeast growth, temperature control for prevention of excessive heat and the prevention of oxidation. Enzymes in the yeast act like catalysts, they speed up the reaction of fermentation. These enzymes are specially designed to speed up fermentation and will not work in other reactions. Temperature control during alcoholic fermentation is necessary to (1) facilitate yeast growth, (2) extract flavours and colours from the grape skins, (3) permit accumulation of desirable by-products, and (4) prevent undue rise in temperature, denaturing the yeast cells. Wine making and bread making are two examples of biotechnology, this means using microbes, plant cells or animal cells to make substances that are useful to us. Many useful chemicals have been produced using fermentation techniques.
There are many experiments to test that
Yeast + water + glucose ↦ CO2 + Ethanol. One of these is to use two test tubes one filled with yeast suspension plus diazine green and liquid paraffin on top. This is to prevent oxygen reaching the yeast. The other is filled with hydrogen carbonate indicator solution and the test tubes are connected with a delivery tube. This test is to see whether yeast can respire anaerobically (Without air). If the hydrogen carbonate indicator solution turns yellow it means that no oxygen was present when the yeast respires. However, if the hydrogen carbonate indicator stays pinkish colour oxygen was present when the yeast fermented. Another previous test has proved that oxygen is not necessary for respiration. The method for this test is to put a yeast and glucose solution into a boiling tube along with two drops of diazine green. This is to indicate when all the oxygen has been removed because in the presence of oxygen it is blue and when no oxygen is present it turns pink. Then liquid paraffin is added to the top of the solution creating a seal so no more oxygen can get in. When the diazine green turns pink indicating that the yeast has used up all the oxygen, a bung on top of the boiling tube with a delivery tube is placed in the mouth of a test tube filled with hydrocarbonate indicator solution. If the yeast has respired the cabon dioxide from the solution will turn the hydrocarbonate indicator yellow.
Predictions
One of the factors that will speed up the fermentation of yeast is the temperature at which the yeast respires. My prediction is that yeast can ferment faster at a temperature of 380c than it will at room temperature (240c). I believe this because when an object or organism is given heat energy the object will speed up whatever it is doing. This is because the particles of the object are given energy so they speed up, therefore increasing the speed of the reaction. However this does not happen with enzymes as they are living and work best at 380c which is body temperature. I think this will work with yeast cells as long as the temperature does not exceed 500c. If the temperature does go higher than this the enzymes in the yeast cells will be de-natured and die.
To test this prediction I will measure the rate at which carbon dioxide is produced from the fermentation of yeast which has been heated to a temperature of 380c. I will then compare this to the rate at which carbon dioxide is produced from yeast kept at room temperature (approximately 240c). If the yeast in the heated boiling tube produces 1ml of CO2 faster than the yeast at room temperature then this will show that temperature does have an effect on the speed at which yeast ferments.
This is a prediction of the results I expect from my experiment.
Predicted Results
A Graph Predicting the Effect of Temperature on the Speed of Carbon Dioxide Production
Apparatus list:
2 x Bunsen burners or water baths
2 x boiling tubes with two holes in the bung (the first to hold a thermometer and the second to hold a syringe that shows how much carbon dioxide is produced).
Yeast
Water
Sugar
2 x tripods
Beakers
Gauzes
2 x stop clocks
Method
Measure out the amounts of yeast, water and sugar that will be needed in the experiment. Then fill two beakers half full of water and heat one of them to 380c and leave the other at room temperature. Put the two boiling tubes in the beakers of water. Then add the yeast, water and sugar into the boiling tubes and start the timer. Record how long it takes for 1ml of carbon dioxide to be produced in each boiling tube.
Fair test: I will repeat this test five times to make sure I get reliable results. I will only change one variable and that will be the temperature.
By Daniel Wingrove
