Fun with Fermentation
What is fermentation?
 Any of a group of chemical reactions that split
complex organic compounds into relatively simple
substances without oxygen.
Yeast Enzymes
 Example: Sugar  ethanol and carbon dioxide
 Enzyme: Any of numerous complex proteins that are
produced by living cells and catalyze specific
biochemical reactions
(Merriam Webster)
 Catalyze: Cause or accelerate
Ethanol Production
GLBRC, 2010
 Glucose is a simple sugar
 Carbohydrate-Carbon, Hydrogen, and Oxygen
 Produced by plants
 Glucose linked together by bonds makes starches
and cellulose
 Glucose linked together by bonds
 What are some examples of starch?
 What is the purpose of starch?
 Glucose linked together by bonds
 Where is cellulose?
 What is the purpose of cellulose?
Fermentation in a bag
 Materials
 Sugar
 Ground Corn
 Grass clippings
 Yeast
 50 mL or ¼ cup of hot water
 Snack size Ziploc bags or balloons
Fermentation in a bag
 Instructions
 Add 1 teaspoon of the feedstock, 1 teaspoon of yeast, and 50
mL of warm water to the Ziploc bag
 Close the bag, try to remove as much air as possible
 Allow the bag to set for at least 15 minutes
Pre Experiment Questions
 Which bag contains the most CO2 after a certain
period of time?
Do you think the amount of CO2 production is
different based on the feedstuff tested?
Why do you think the amount of CO2 production will
be different?
Which feedstuff do you think will produce the most
Which feedstuff do you think will produce the most
Why does fermentation vary among feedstuffs?
 Sugar=glucose
 Corn=starch
 Grass=cellulose
Starch vs Cellulose,+Polysaccharides+and+Lipids
Alpha 1,4 vs Beta 1,4
 Alpha 1,4 bond is broken by common enzymes, such
as amylase, or acid treatments
 Beta 1,4 bond is not easily broken, humans and
animals do not have the enzyme necessary to cleave
this bond
 Based on the results of this experiment can yeast
break the alpha 1,4 or the beta 1,4 bond?
 Which feedstuff fermented the most? How do you
 What gas accumulated in the bag and based on the
reaction equation what else was produced?
 Why did the amount of fermentation vary among the
 In general what do you think is the carbohydrate
content is for the feedstuffs tested?
How is corn used for ethanol production?
 Corn is starch
 Starch is glucose linked by alpha 1,4 bonds
 Yeast cannot break the alpha 1,4 bonds
 Enzymes or acid first break the alpha 1,4 bonds and
free single glucose molecules
 Enzymes: amylase
Why use cellulose?
 Cellulose makes up over half of plant biomass
 This makes cellulose very abundant
 Cellulose has potential to be the largest biofuel
Why Switchgrass?
 Biomass
 Easy to grow
 Marginal Lands
 High Temperature
 Drought Tolerate
 Perennial
The trouble with cellulose…
 Cellulose is wrapped in lignin and
 These components have to be
detangled in order to get to the
 This process is called pretreatment
GLBRC, 2010
 Most expensive part of the process
 Active research looking for enzymes or chemicals to
help with the process
 Many bacteria and fungi can produce cellulase
 Or scientist will genetically modify yeast or other
GLBRC, 2010
New Research
 Before a pretreatment (cooking switch grass in hot
water for 10 minutes) only 10% of cellulose was
available for fermentation after pretreatment 90% of
cellulose was made available for fermentation
 Fall switchgrass given a pretreatment and
fermentation with special yeast could produce as
much as 800-1,000 gallons of ethanol per acre per
year, compared with 150-250 gallons per year
without pretreatment.
 Corn ethanol from grain produces about 500-600
gallons per acre per year

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