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In this experiment, students investigate the process for fermentation in resealable bags with yeast, warm water, enzymes, and various sources of sugars from plants. Students will observe and measure the inflation of the bag as the reaction produces gas (CO2) during the production of ethanol. Students will set up several bags to compare how yeast ferments simple sugars, starch, and complex carbohydrates. Students can compare the rates of ethanol productions and the effects of different enzymes using the inflation of the bag, inflation of balloons, water, or breathalyzers. This lab is used to explore and understand the process of ethanol production as a biofuel.
Ethanol is a renewable source of fuel for vehicles that is widely produced from corn. Ethanol production is reliant on anaerobic fermentation of corn sugars by yeast. Scientists and industry professionals are always working to make the fermentation procedure more efficient. Different enzymes are added to the corn to break the starch into simple sugars that the yeast can process into ethanol. This lab allows students to experiment with different variables in the fermentation process to determine their effect.
When a fuel, such a gasoline, is burned, carbon is released into the atmosphere in the form of carbon dioxide. Burning fossil fuels adds extra carbon dioxide to the atmosphere. This extra carbon dioxide traps heat from the sun and is a major contributing factor in climate change.
Ethanol made from corn also releases carbon dioxide into the atmosphere, but unlike burning fossil fuels, corn plants have already absorbed the CO2 from corn grown last season. This means that by using ethanol we can cycle carbon dioxide between the plants and atmosphere, as opposed to releasing fossilized carbon from oil.
Science Performance Expectation
Science Disciplinary Core Ideas
Science Practices
This lab contains materials that students might consider edible. Remind students that while working in a lab, all materials should be considered dangerous and not be tasted. There should be no eating or drinking in the laboratory. Students should wear appropriate eye protection.
Length of Time for Preparation: 1 hour
Length of Time for Classroom Teaching: 1 class period for the lab and 1 class period for discussion and wrap up.
This lab can be used in classrooms without a lot of lab equipment. The entire lab can be completed with items found at a local store. Teachers can choose to teach the lab in two ways.
Students can choose the feedstock and enzymes to try to figure out which produces the best results.
1. Mix 2.0 mL of amylase concentrate with 98 mL of distilled water to produce a 2% solution. Stir thoroughly.
2. Mix 2.0 mL of glucoamylase concentrate with 98 mL of distilled water to produce a 2% solution. Stir thoroughly.
Fermentation is an anaerobic process (without oxygen), carried out by yeast, bacteria, and even muscle cells. This is an alternative pathway for organisms to release energy from food when oxygen is not available. Yeast and muscle cells can carry out both aerobic respiration and anaerobic fermentation, providing an energy source when oxygen is scarce. The first step in both aerobic and anaerobic respiration is the breaking of a glucose molecule, called “glycolysis”. This yields two new ATP molecules (cellular fuel) per molecule of glucose broken. If oxygen is not available, the cell needs to recycle the molecules needed in order to break more glucose. In doing this, it converts the broken pieces of glucose (pyruvate) into different molecules. Yeast convert the pyruvate into ethanol, which is a renewable fuel source. This process also produces two carbon dioxide molecules for each glucose molecule fermented. Students can determine the rate and amount of fermentation by measuring the amount of carbon dioxide it produces, as shown in the equation below.
In this activity, students will be using yeast, which needs glucose to break for fuel. Glucose and fructose are both simple sugars, but the ethanol industry feeds yeast corn, in which most of the sugars are contained in long chain molecules, or polymers called “starch”.
Several enzymes have the purpose of breaking starch up into smaller pieces, which are more useful for the yeast. Amylase is an enzyme that breaks starch into smaller pieces, while glucoamylase is more specialized in removing individual glucose molecules from the ends of the starch. Being proteins, enzymes have specific conditions in which they function more effectively, such as pH and temperature.
If you are teaching this as a standalone lesson:
Possible topics for discussions before beginning this lab depending on what has been previously taught:
If you are teaching this as a larger unit, and using this lab to build understanding for making ethanol, you would want to discuss biofuels and the benefits of producing ethanol.
Option 1: Teacher Designed Experiment
Divide the students into lab groups. Assign each group one of the feedstock option
a. (Feedstock ex. corn starch) no enzymes
b. (Feedstock) amylase
c. (Feedstock) glucoamylase
d. (Feedstock) both enzyme
Optional:
Students can use an ethanol probe or breathalyzer to compare relative differences in ethanol concentrations. Breathalyzers are designed for measuring blood alcohol content in people; therefore, the readings will not tell you directly how much ethanol in each sample. Still, the readings can be used to determine if ethanol was produced and to make comparisons in ethanol production between the various feedstocks.
Option 2: Student Designed Experiment
Prepare before the start of the lab
Identify the different variables in this experiment. Students choose a variable that they would like to investigate.
Teacher Tips
Using a feedstock that is a simple sugar will yield the most rapid results. Feedstocks with a starchy composition will not ferment well. Yeast does have the enzymes required to break down starch into glucose but this happens very slowly so you see little fermentation.
Teacher Resources
This can be done as a standalone lab or it can be done as part of a larger unit covering ethanol production. This lab is designed to introduce the fermentation process using yeast and a combination of enzymes. The next labs in sequence are Ethanol: Corn Mash and Distillation and DDG Nutrient Testing (MS).
The following questions will allow the students to review what they have learned and apply this new knowledge in the fermenting of ethanol lab.
To learn more about agriculture careers visit https://agexplorer.ffa.org/.
Any educator electing to perform demonstrations is expected to follow NSTA Minimum Safety Practices and Regulations for Demonstrations, Experiments, and Workshops, which are available at https://static.nsta.org/pdfs/MinimumSafetyPracticesAndRegulations.pdf, as well as all school policies and rules and all state and federal laws, regulations, codes and professional standards. Educators are responsible for abiding appropriate legal standards and better professional practices under a duty of care to make laboratories and demonstrations in and out of the classroom as safe as possible. If in doubt, do not perform the demonstrations.
This lesson is the work product of the Kansas Corn Commission. Our lessons are written in collaboration with Kansas teachers for use in the classroom. Teachers may copy and share this curriculum. Use of this product for commercial or promotional use is prohibited without express permission of Kansas Corn.
As the need to produce more food with less resources grows, it is important that future generations have a better understanding of agriculture and how corn farming and agriculture fit into our daily lives. That’s why the Kansas Corn STEM program provides lessons to teach science through the lens of corn. We are committed to providing free materials and training to support educators.
