The Effect of Yeast and Temperature
on the Alcohol Content of Zea Maize
after Fermentation
Madeline LaBelle—Warren Mott High School
Keara Miley—Lake Shore High School
Background
•
•
•
•
Petroleum oil supplies are being depleted
They are being used up rapidly
A sufficient alternative is needed
Biofuel can be used instead
– Made from renewable biomass resources
– Safe and environment friendly
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Background
• Biofuel emits 51% less greenhouse gases than
fossil fuel
– More efficient methods of production
• Due to new technologies
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Background
• Biofuel is made from the fermentation of
plant matter
• Fermentation is the process in which yeast
and enzymes break down sugars and convert
them into alcohol
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Background
• Alcohol content is directly related to how well
a material can be used as a biofuel
– The higher the better
• The higher the alcohol content, the hotter is
burns and the better it is for a car’s engine
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Background
• Cars have combustion engines
• How a combustion engine works
– Increase in pressure from combustion expands the
cylinder
– Pushes piston and causes crankshaft to turn
• The hotter a material burns, the more
combustion
– More efficient
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Background
• Different types of biofuel
– Corn ethanol
– Cane ethanol
– Cellulosic ethanol
• Cane ethanol is most efficient
• Corn ethanol is the most common in America
– Corn is the most abundant source here
– No import taxes
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Background
• Two different corn ethanol production
processes
– Dry milling
– Wet milling
• Dry milling is the most common
• Wet milling is more extensive but produces
more byproducts
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Dry Milling
• Kernels ground up, enzymes and water added
– Called mash
– Enzymes break down starches into sugar
• Mash heated to reduce bacteria
• Mash is cooled and yeast added
– Fermentation starts
• When fermentation finished, it is distilled
– Distillation separates substances
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Wet Milling
• Kernels soaked and the middle is removed
– Used to produce corn oil
• Starch and gluten separated
– Gluten used for animal feed
• Water and enzymes added to ferment
– Remaining starch used to make corn syrup
• Mixture distilled and sent to oil companies
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Terminology
• Zea maize
– Corn
• Saccharomyces cerevisiae
– Type of yeast
• Hydrometer
– Tool used to measure alcohol content of a material
• DOE
– Design of experiment
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Purpose
• To find a way to make corn ethanol more
efficient by increasing the alcohol content
– Different temperatures during fermentation
– Different amounts of yeast added to the mixture
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Problem Statement
What amount of Saccharomyces cerevisiae and
what temperature during fermentation would
yield the highest alcohol concentration in Zea
maize?
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Hypothesis
Out of all amounts of Saccharomyces cerevisiae
(1, 2, and 3 grams) and temperatures (22, 25,
and 28 °C), 3 grams of yeast at a temperature of
22 °C will yield the highest concentration of
alcohol in fermented corn.
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Data Measured
• Dependent variable
– The alcohol content of the fermented corn (%)
• Independent variables
– The amount of yeast (grams)
– Temperature during fermentation (°C)
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Materials
• Active dry yeast
(Saccharomyces
cerevisiae)
• 21 half-bushels of corn
• 21 emptied two liter
bottles
• Scale
• Funnel
• Balloons
•
•
•
•
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Blender
Hydrometer
Mesh colander
Incubator (set at 22,
25, and 28 °C)
16
Blender
2 Liter Bottle
Funnel
Scale
Graduated Cylinder
Hydrometer
Balloon
Active Dry Yeast
Corn
Mesh Colander
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Procedure
• Blend corn mixture together and measure
alcohol content with hydrometer
• Add yeast to mixture (amount dependent on
trial)
• Pour mixture into a 2 Liter bottle with the
funnel
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Procedure
• Place bottle in incubator (temperature
dependent on trial)
• After four days, remove the corn mixture and
measure alcohol content with hydrometer
• Subtract second alcohol measurement from
the first
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Procedure
• Record the value in the table
• Repeat for each combination of temperature
and amount of yeast
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Procedure Video
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Data
High and Low Values
Temperature (°C)
Amount of Yeast (g)
-
Standard
+
-
Standard
+
22
25
28
1
2
3
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Data
Design of Experiment Data
Order
Run
1
Standard
2
Result
Order
Run
6
1
Standard
++
7
2
3
--
5
4
Standard
5
Order
Run
6
1
Standard
6
++
7
2
++
8
3
--
5
3
--
6
6
4
Standard
5
4
Standard
8
+-
8
5
+-
7
5
+-
8
6
-+
5
6
-+
5
6
-+
6
7
Standard
7
7
Standard
6
7
Standard
6
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Result
Result
23
Data
Standard Trials
6
7
6
5
6
6
6
6
8
7
6
Alcohol Content (%)
6
5
4
3
2
1
0
0
1
2
3
4
5
6
7
8
9
Trial
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Data
Runs
First DOE
Second DOE
Third DOE
Average
Temperature
(°C)
Amount of
Yeast (g)
+
+
7
7
8
7.33
-
+
5
5
6
5.33
+
-
8
7
8
7.67
-
-
5
5
6
5.33
Grand Average: 6.145
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Observations
Date
Observation
Oct 22
9 standard trials are set up. Corn and yeast blends are consistent.
Oct 26
Corn and yeast blend produced CO2 which can be seen by the
balloon inflating.
Oct 29
All (+,-) trials produced CO2 and the balloons inflated.
Nov 2
Only 3 (+,+) trials produced CO2. The balloon on the Trial 2 bottle
did not inflate resulting in a redo of this trial.
Nov 6
All (-,-) trials produced CO2 and the balloons inflated.
Nov 10
All (-,+) trials produced CO2 and the balloons inflated.
Nov 13
Trial 17 (-,+) blend seemed more separated than the rest, but still
produced CO2 and stayed consistent with rest of trials.
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Data Analysis and Interpretation
• A Two Factor DOE was used
– Temperature (°C)
– Amount of yeast (g)
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What is a DOE?
• DOE stands for a Design of Experiment
• DOE measures the individual effects and
combined effects of different factors
• Appropriate for this experiment because two
different factors were manipulated at two
levels
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Data Analysis and Interpretation
• The effect of temperature
on the alcohol content of
fermented corn was 2.17
units
• As temperature increased,
the alcohol content
increased by 2.17 units
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Data Analysis and Interpretation
• The effect of the amount of
yeast on the alcohol
content of fermented corn
was -0.17 units
• As the amount of yeast
increased, the alcohol
content decreased by 0.17
units
10
Alcohol Content (%)
8
6.33
6.5
6
4
2
0
-1
1
Amount of Yeast (g)
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Data Analysis and Interpretation
• The effect of temperature
and yeast has an effect of
-0.17 units
• There may be an
interaction between the
two effects because the
slopes are not parallel
10
Alcohol Content (%)
8
6
7.67
7.33
5.33
5.33
-1
1
4
2
0
Amount of Yeast (g)
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Determining Significance
• Any effect that is greater than two times the
range of standards is deemed significant
• None of the variables were considered
significant in this experiment
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Conclusion
• The hypothesis was rejected
• Neither temperature during fermentation or
amount of yeast had a significant effect on the
alcohol content of corn after fermentation
• These results of this experiment agree with
current work in this field
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Why Did These Results Occur?
• The amount of yeast had no effect because
yeast can only convert the sugars that are
present in the mixture and after these sugars
are converted can do no more
• Temperature will only speed up the process
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What Will Have an Effect?
• The only factor that will have a significant
effect on the amount of alcohol in a material
is the amount of sugar in a material
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Sources of Error and Weakness
• Incubator temperatures fluctuated slightly
• Yeast was left in water to rehydrate for longer
than necessary
• Balloon did not always inflate with carbon
dioxide during fermentation
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Recap
• An alternative fuel source is needed to replace
fossil fuels
– Biofuels (ethanol)
• Made from fermented plant matter
• High alcohol content is directly related to how
well a biofuel can be used
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Recap
• What amount of yeast and at what
temperature during fermentation will yield
the greatest alcohol content?
• The hypothesis was that 22 °C and 3 grams of
yeast would yield the highest alcohol content
– Hypothesis was rejected
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Recap
• Corn, water, and yeast were blended and
poured into a two liter bottle with a balloon
placed around the mouth
• The bottle was placed into an incubator to
ferment
• Alcohol content was taken using a hydrometer
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Recap
• A two factor DOE was used
– Temperature (°C)
– Yeast (g)
• Neither variable had a significant effect
– Yeast can only convert the sugars that are present
– Temperature speeds up the process
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Real World Applications
• This information can be used by the fuel
industry by saving time, money and resources
used during the production of biofuel
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Further Research
• Rerun the experiment using different
materials such as sugar cane, beats, or switch
grass. Experimenting with different plants
could help find an abundant source that
would be more efficient
• Use and compare different types of yeast
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Acknowledgements
• Skip Walker
– Works at local brewery
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Works Cited
• "Biofuel Info." Information about Biofuel, What Is Biofuel,
Renewable Energy Solutions, Ethanol Uses. Biofuel Watch,
2010. Web. 18 Sept. 2012. <http://www.biofuelwatch.org/>.
• Curry, Jim. "Yeast and Fermentation." MGreisMeyer. Dukes of
Ale BJCP Preparation
Course, 19 Apr. 2009. Web. 18
Sept. 2012.
<http://www.mgriesmeyer.com/doatest/bjcp/yeastAndFerme
ntation.pdf>.
• "Dry Mill Ethanol Production." Ethanol Info. N.p., n.d. Web. 12
Oct. 2012.
<http://people.hws.edu/environmentalstudies/Ethanol%20Inf
o/Dry%20Mill.html>.
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Works Cited
• "Fermentation: World of Microbiology and
Immunolgy." Fermentation. Ed. Brenda Wilmoth Learner. N.p.:
n.p., n.d. N. pag.Gale Virtual Reference Library. Web. 9 Sept.
2012.
<http://go.galegroup.com/ps/retrieve >.
• Janson, Lee W. Brew Chem 101: [the Basics of Homebrewing
Chemistry]. North Adams, MA: Storey, 1996. Print.
• "Practical and Theoretical Considerations in the Production of
High Concentrations of Alcohol by Fermentation."
ScienceDirect.com. N.p., n.d. Web. 05 Dec. 2012.
• "Some Interesting Oil Industry Statistics." Oil Industry
Statistics from Gibson
• Consulting. N.p., n.d. Web. 05 Dec. 2012.
LaBelle -- Miley
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Works Cited
• Stairs, David. Yeast. Portland, Or.?: D. Stairs, 1999. Print.
• "Wet Mill Ethanol Production." Ethanol Info. N.p., n.d. Web.
12 Oct. 2012.
<http://people.hws.edu/environmentalstudies/Ethanol%20Inf
o/Wet%20Mill.html>.
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