Fermentation

Overview

In this activity, you will investigate the process of fermentation in yeast. You will test the ability of yeast to perform fermentation at different temperatures and with different carbohydrates. You will also test three additives to determine their affect on fermentation.

Materials

Each lab group will need the following materials:

  • yeast
  • glucose
  • lactose
  • sucrose
  • maltose
  • water
  • lactase tablet
  • MgSO4
  • NaF
  • incubator set at 37°C
  • wax pencil
  • 9 fermentation tubes

Before You Begin

Discuss the following questions with your lab group.

  1. What is the preferred energy source of the all cells?
  2. What types of sugars are being used in each tube (monosaccharide, disaccharide, etc)?
  3. What effect should temperature have on the fermentation reactions?
  4. What does CO2 indicate in these tubes?
  5. What do you think the additives do? What effect will they have?

Method

  1. Label the top of each fermentation tube using the wax pencil.
  2. Fill the tubes as shown in the table below.
  3. Eliminate the air bubble in the sealed end of the fermentation tube by tilting the tube.
  4. Place a rubber stopper into the open end of the fermentation tube and place at the appropriate temperature for an hour.
    • Make sure to keep the wax label above the water in the incubator.
  5. While you wait, predict the amount of CO2 gas that will be generated in each tube. Use symbols like +, ++, and +++ to indicate CO2 levels.
  6. After one hour, measure the size of the CO2 bubble in the tube. Record your data in cm.
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