EDUCATION AND OUTREACH
Fermentation In A Bag
Overview
This classroom activity is a basic experiment that allows students to observe the process of fermentation
and the challenge of producing ethanol from cellulosic sources. Students combine yeast and warm
water with a feedstock in a “snack” size resealable zipper bag and observe as the yeast “eats” the
feedstock such as sugar, cornmeal, or sawdust, and produces carbon dioxide and ethanol. Younger
students can observe fermentation in a single bag, while older students can create multiple set-ups
to compare how yeast reacts with different feedstocks. This can also be done at family-style outreach
events and science fairs.
Basic Experiment
Using sucrose (table sugar) as a feedstock will yield the most rapid results. Some of the alternate
feedstocks we had available include: corn meal (students could even grind their own corn), corn stover
powder, and sawdust. Additional alternatives could include finely ground grass clippings, dead leaves,
composting materials, etc. Students should remove as much air as possible from the bag after filling it
with materials. As the yeast produce carbon dioxide, the bag will inflate – it may even pop!
Fermentation in a bag – Recommended Recipe:
• In a snack size resealable zipper bag, combine 1 tsp. of sugar (or another feedstock) and 1 tsp. of yeast.
• Add 50mL (1/4 cup) of warm tap water and zip the bag closed, removing as much air as possible.
• Mix gently. Lay bag on a flat surface or gently carry with you and watch for results – fastest results
should be achieved in 15 minutes.
• Warning: Be sure to release the gas before 1 hour has elapsed or the bag may spill open!
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Fermentation In A Bag
Labels:
On each bag is a label explaining the activity. These labels can be downloaded from the GLBRC Educational
Materials page, under supporting materials for this activity. Below is the sample label:
Ingredient
Fermentation in a Bag!
Recommended
Actual
Yeast
1 tsp.
______________
Food Source
1 tsp.
______________
Warm Water
50 ml
______________
Food Chosen: _________________
Start Time: ______________
Questions to discuss at the table:
1. If the bag is inflating, what is filling it up?
2. Are you observing fermentation? How do you know?
3. How did the yeast respond to different kinds of “food”?
4. If sugar is yeast’s favorite “food”, why might plant materials be fermented to create ethanol?
5. Why do you think one sugar source or plant material may work better as a fuel than another? (Use the
poster graphics on pg. 4 of this handout to help.)
Supply List for the Basic Experiment
o Hot water source
o 2-4 Liter Thermos (with spout) for hot tap water
o 2 Small Graduated Cylinders (100mL)
o Measuring Spoons (one teaspoon for each feedstock source and the yeast to avoid cross-contamination)
o Dry Active Yeast (one 4 oz. jar contains approximately 36 teaspoons of yeast, will make 36 bags)
o Sugar
o Cornmeal, Corn Stover Powder, Sawdust, and any other sample feedstocks to use in experiments
o Resealable zipper bags (“snack” size) with fill-in labels (found on our educational materials page).
o Paper towels
Science Fair Information
Prep time: 30-60 minutes, depending on event/group size
Demo/Activity time: 10 minute set-up, observe for 15 minutes or up to 1.5 hours.
Students ran this experiment at a GLBRC table at a family-oriented “science fair” event. The table was set up
so that the experiment had two main options: completion of a comparison Fermentation In A Bag experiment
at the event, or prefilled dry materials bags for take home completion (containing yeast and sugar) so all
parents/students had to do was add warm water and observe. The option of providing prefilled bags with
direction labels allowed many families who were in a rush to take the activity home and complete it later.
Empty bags had labels with fill-in-the-blank style directions for students to design their own comparison
experiment. Also on the table were several materials on display to help explain the creation process of
cellulosic ethanol, from feedstock to the final fuel.
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Fermentation In A Bag
Extra Supplies for the Science Fair Set-Up
o Corn grinder and field corn, for students to make their own corn meal which could be used in their
comparison fermentation experiments.
o Small samples of feedstocks and their pretreated partners (e.g. corn stover and AFEX-treated corn
stover, switchgrass and AFEX-treated switchgrass. AFEX = Ammonia Fiber Expansion)
o 2-3 Baking sheets (under set-up area to prevent spilling messes)
o Resealable zipper bags with take-home labels, prefilled with yeast and sugar
o Large samples of switchgrass and corn plants (behind table, for display)
o Pens
o Mini-Fermenter/bioreactor – a demonstration sized fermenter (see attached pictures) to display what
fermenters in the lab might look like.
o Samples of Ethanol and Soybean biodiesel, for observation
o Handouts: a copy of the poster behind the table, a word-search and maze about cellulosic ethanol and
biofuels for kids, and bookmarks with fun facts about ethanol
o Poster (on pg. 4 of this handout, as well as in supporting materials for the activity on our website)
Table Set-up. Left to right: Students could try to grind corn with an old-fashioned grinder. This corn meal could be used in
comparison fermentation experiments. Fermentation in a bag activity and supplies. Sample feedstocks, with AFEX pretreated
comparisons. Sample biofuels (ethanol and biodiesel). Bookmarks and puzzle handouts.
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Poster. Image on the left: Cellulosic Biofuel Production Steps, taken from DOE image gallery (http://genomics.energy.gov/gallery/).
Images on the right were created by GLBRC.
Copyright © 2010. All rights reserved.
This document may be reproduced for individual classroom use, or the equivalent, only.
All other uses are prohibited without written permission from the Great Lakes Bioenergy Research Center.
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