Fermentation of Sugar

By: Zule Barrientos


I will have to determined whether yeast are capable of metabolizing a variety of sugars. Although the aerobic fermentation of sugars is much more efficient, in the experiment we I will have to have yeast ferment the sugars anaerobically. When the yeast respire aerobically, oxygen gas is consumed at the same rate that CO2 is produced. Their will be no change in the gas pressure in the test tube. When the yeast ferment the sugars anaerobically, however, CO2 production will cause a change in the pressure of a closed test tube, since no oxygen is being consumed. I can use this pressure change to monitor the fermentation rate and metabolic activity of the organism


1-conect the gas pressure sensor to the computer interface. prepare the computer for data collection by opening the file "12B" Fermentation (Pressure ) from the (Biology with Vernier folder)

2- connect the plastic tubing to the valve on the has pressure sensor.

3- prepare a water bath for the yeast. A water bath is simply a large beaker of there at a certain temperature. This ensures that the yeast will remain at a constant and controlled temperature. To prepare the water bath, obtain some warm and cool water from your teacher. Combine the warm and cool water into the 1 liter beaker until it reaches 38-40C. The beaker should be filled with about 600-700mL water. place the thermometer in the water bath to monitor the temperature during the experiment.

4- Obtain two test tubes and label them I and 2

5- test two of the four sugars solutions, obtain two of the four sugar solutions: Glucose Lactose and the one other sugar solution, as directed by your instructor. place 2.5 mL of the first sugar solution into test tube 1 and 2.5mL of the second sugar solution into test tube 2. Record which solutions you tested in table 1.

6- set the test tubes into the water bath.

7- obtain the yeast suspension . gently swirl the yeast suspension to mix the yeast that settles to the bottom. using a 10mL pipette or graduated cylinder, transfer 2.5mL of yeast into test tube 1. gently mix the yeast into the sugar solution, be gently with the yeast they are living organism.

8- in the test tube, place enough vegetable oil to completely cover the surface of the yeast/glucose mixture. be careful to not get oil on the inside wall of the test tube. set the test tube in the water bath.

9-insert the single-holed rubber-stopper into the test tube.

10- incubate the test tube for 10 min in the water bath. temperature should be constant.

11- when incubation has finished, connect the free end of the plastic tubing to the connector in the rubber stopper.

12- click COLLECT to begin data collection. maintain the temperature of the water bath during the course of the experiment. data will collected for 15min.

13-monitor the displayed in the meter. if the pressure exceeds 130kPa, the pressure inside the tube will be too great and the rubber stopper is likely to pop off. disconnect the plastic tubing from the gas pressure sensor if the pressure exceeds 130kPa.

14-when data collection has finished , disconnect the plastic tubing connector from the rubber stopper. remove the rubber stopper from the test tube and discard the contents in a waste beaker.

15- the stores the data so it can be used later, but it will still be displayed while you collect data for the second test tube

16- repeat steps 7-14 using test tube2.

17- click the linear fit button click OK a best fit linear regression line will be shown for each of your runs. table 1 record the value of the slope M for each of the s=test tubes.


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