Lactase Experiment– Logger Pro

This activity is based on Experiment 24A: Lactase Action (CO2 Sensor) in the book Biology with Vernier written by Kelly Redding and David Masterman and is used with permission.

  1. 1.Open Logger Pro software.
  2. Click on File Open and open the Biology with Vernier folder.
  3. Open the program titled 24A Lactase Act (CO2).
  4. Connect the LabQuest Mini to the computer using the USB cable.
  5. Connect the CO2 gas sensor into CH 1 of the LabQuest Mini using the British Telecom connector.Do not allow the CO2 sensor to get wet; the circuit board inside the sensor will be ruined if it gets wet.
  6. Set the CO2 gas sensor switch to the Low (0-10,000 ppm) setting. The switch is on the side, near the top of the sensor.
  7. Click on the button to set the Length of Experiment to 13 minutes.

  1. Design and draw an appropriate data table in your Laboratory Journal in order to record your results. You will test the response of yeast to each solution once. Re-read the Introduction if you are unsure of which solutions you will be testing or what you will be measuring.
  2. Label the test tubes with the names of the solutions you will be testing (water, glucose, milk, milk & lactase).
  3. Put on your goggles.
  4. Crush the pharmaceutical tablet containing the lactase enzyme. Use a mortar and pestle or crush it as instructed by your teacher. Make sure the tablet is crushed to a powder and that there are no large pieces.
  5. Dissolve the crushed tablet in 20 mL of room temperature water. Try to dissolve as much of the tablet as possible by carefully swirling the water in the mortar or as instructed by your teacher.
  6. Measure and add 2.5 mL of water to the test tube labeled water.
  7. Measure and add 2.5 mL of the glucose solution to the test tube labeled glucose.
  8. Measure and add 2.5 mL of the room temperature milk to the test tube labeled milk and to the test tube labeled milk & lactase. Do not add the lactase yet.
  9. Pour the water from the first test tube into the BioChamber.
  10. Add 2.5 mL of the yeast suspension to the BioChamber.
  11. Swirl the chamber gently to mix the contents.
  12. Carefully place the CO2 sensor in the opening of the BioChamber, see the diagram below. Do not allow the sensor to come in contact with the solution in the BioChamber.
  1. Wait 90 seconds for the sensor to equilibrate.
  2. Click the green Collect button on the top toolbar to begin data collection.
  3. Name the file when requested and save it as instructed by your teacher. Record the file name in your Laboratory Journal. If your teacher says you have time to do the data analysis the same day you run the experiment, continue to steps 23 to 25. If your teacher instructs you to collect all the data and says you will do the analysis another day, then skip to step 26.
  4. Examine the CO2concentration graph and find where the concentration increases linearly. Move the mouse pointer to the point where the concentration values begin to increase linearly and hold down the mouse button. Drag the pointer to the point where the pressure begins to level off and release the mouse button.
  5. Click the Linear Fit button, , to perform a linear regression. A floating box will appear with the formula for a best fit line.

  1. Record the slope of the line, m, as the fermentation rate in your Laboratory Journal. The rate is expressed as parts per million of CO2 per minute.
  2. Remove the CO2sensor from the BioChamber and carefully place it aside.
  3. Empty the contents of the BioChamber down the sink and rinse the chamber with running water. Be sure it is completely clean.
  4. Dry the inside top portion and the outside of BioChamber using a paper towel.
  5. Pour the measured glucose solution from the test tube labeled glucose into the BioChamber.
  6. Repeat steps 17 to 28 using the glucose solution.
  7. Pour the milk from the test tube labeled milk into the BioChamber.
  8. Repeat steps 17 to 28 using the milk solution.
  9. Pour the milk from the test tube labeled milk & lactase into the BioChamber.
  10. Add 8 drops of the solution you made with the crushed pharmaceutical tablet to the milk in the BioChamber.
  11. Add 2.5 mL of the yeast suspension culture to the BioChamber.
  12. Repeat steps 18 to 28.

Optional Extension

  1. Test for the presence of glucose in the glucose solution. Place a glucose test strip in a few drops of the glucose solution. Notice the color change on the test strip.
  2. Test for the presence of glucose in the milk. Place a glucose test strip in a few drops of milk. Notice the color change on the test strip.
  3. Test for the presence of glucose in the milk mixed with lactase. Place a glucose test strip in a few drops of the milk with lactase solution. Notice the color change on the test strip.

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BI – Lactase Experiment– Logger Pro– Page 1