Can Yeast Ferment Polysaccharides as Efficiently as Disaccharides?
Difficulty of Project (Easy, Medium, Hard)
Grade Level (Elementary, Middle, High School)
Wear safety goggles when handling glassware such as volumetric flask, test tubes, and glass droppers. Material Availability (Are the materials required readily available?) The material can be found in any high school laboratory. Sucrose, Maltose, and Cellulose can be ordered from chemical supply catalogs.
Approximate Time Required to Complete the Project (Hours, days, weeks)
To compare the rate and determine the efficiency of polysaccharide fermentation by yeast.
The project goals include measuring the rate of disaccharide fermentation and comparing the rate with polysaccharide fermentation.
Materials and Equipment / Ingredients
Fermentation involves the anaerobic break down of sugar molecules. As sugar ferments in the absence of oxygen, carbon dioxide is released as a byproduct of fermentation. Suspending yeast in sugar and tepid water initiates the process of fermentation. As fermentation ensues, carbon dioxide gas is released into the surrounding water. The gas moves through the water in bubbles. Counting the number of bubbles released over time can be used to determine the rate of sugar fermentation. Various disaccharides for comparison include maltose and sucrose and various polysaccharides include starch and cellulose.
What are the products of fermentation?
How can the rate of fermentation be determined?
How is energy stored in food broken down?
How is energy released from food sources?
What is anaerobic respiration?
Terms, Concepts and Questions to Start Background Research
- Prepare a 1 molar solution of sucrose, maltose, and cellulose. To prepare 1 molar solutions measure the molecular mass of each substance using a triple beam balance. The molecular mass of each substance can be determined from the atomic masses of the individual atoms that make up the chemical formula of the substance. The chemical formula and molecular mass of the substances is located on the label of the container.
- Label three volumetric flasks with molar concentration and solution name, for example, 1 molar maltose, 1 molar sucrose, 1 molar cellulose.
- Transfer the weighed substances to a 1 Liter volumetric flask and dissolve in 800 milliliters of distilled water. Once the substance is fully dissolved, add an additional 200 milliliters of distilled water.
- Using a triple beam balance measure 5 grams of yeast onto a tray.
- Remove the rubber end of a dropper and transfer the yeast to fit inside the rubber end of the dropper.
- Reattach the rubber end of the dropper to the glass tube it came from keeping the dropper inverted.
- With the inverted dropper place inside a test tube. The rubber end of the dropper with the yeast inside should rest at the bottom of the test tube.
- Add 4 milliliters of the 1 molar sucrose solution inside the dropper and fill the test tube with tepid water.
- Record the number of carbon dioxide bubbles that evolve from the rubber end of the dropper.
- Repeat steps 4-9 for the solution of maltose and cellulose.
Principles of Fermentation Technology 2nd Edition, P.F. Stanbury, A. Whitaker, and S.J. Hall, 1995, Elsevier Science Ltd.
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