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Background:
This lab provides students with first-hand experience in
the processes involved in fermentation ethanol production from the raw material stage through fermentation and distillation to end products. Teachers should not attempt it without the proper laboratory equipment and
they should follow appropriate lab safety procedures. Additional directions can be obtained from BSCS (Blue) Molecules to Man and The American Biology Teacher, Jan. 1989. (Caution students: This process produces
materials unfit to consume.)
Process skills:
Observing, recording, measuring, inferring, analyzing, interpreting data, and controlling variables.
Preparing The Mash:
You
will need: thermometer, stirring rod, distilled water (preheated and room temperature), balance, beakers (or kitchen pans), Erlenmeyer flasks, lab toweling, pH paper, sulfuric acid, burner apparatus (or hot plate),
safety glasses, corn (shelled, meal, grits, or flour), grinding apparatus (rocks, boards, manual grinder).
Procedure:
1.)In a beaker mix 50g of corn with 300 ml of preheated distilled water.
2.)Add 1 or 2 drops of sulfuric acid to adjust pH to 5. (This step can be eliminated for younger students.)
3.)Bring to a boil, stirring constantly.
4.)Boil for 15 minutes.
DO THE FOLLOWING STEPS WHILE MASH IS BOILING
5.)In an Erlenmeyer flask, mix 12g of ground malt with 100ml of distilled water. (See appendix for malt
sprouting procedures).
6.)In a test tube mix .5g of yeast with 20ml of warm (29C or 85F) water. Add a pinch of sugar and watch for bubbling to show yeast is active. (See appendix for a description of the
fermentation process).
7.)When mash has boiled 15 minutes, remove it from the heat and cool it for 5 minutes, stirring constantly.
8.)Under teacher's supervision, set beaker in warm, cool, then ice water to
hasten cooling. Stir occasionally and check temperature.
9.)Add malt solution when mash has cooled to 63C (145F).
10.)Allow to cool to 28C (83F), then stir in yeast solution.
11.)Cover beaker with a
small plastic bag, or transfer the mixture to an Erlenmeyer flask, and set it up as shown in figure 1
12.)Let stand at room temperature 10 to 14 days.
13.)When bubbling stops, fermentation has ended.
Distillation:
You will need: cloth, beakers, burner set up, flask, stopper, glass tubing, condenser tube, electrical tape, two small graduated cylinders, 4 petri dishes, matches, wood board, lab grade
ethanol, safety glasses.
1.)Set up distillation apparatus as shown in figure 2.
2.)Squeeze fermented mash (beer) through a cloth into the Erlenmeyer flask. OR- Be careful not to disturb the mash and use a
pipette to draw off the top clear layer of liquid.
3.)Transfer liquid or strained beer into distillation apparatus.
4.)The beer should contain about 10% ethanol, so distill into a graduated cylinder the
first 10% of the beer. (Ethanol evaporates first, so you should get mostly ethanol with the first 5ml that are distilled).
5.)Carefully smell the fuel. Compare the smell to lab grade ethanol.
6.)UNDER
TEACHER'S SUPERVISION, pour the ethanol fuel into a pyrex Petri dish and light it with a match. Compare to the burning of lab grade ethanol.
Coproducts:
Since only the starch portion of corn is
used in ethanol production, the remaining coproducts can be used as livestock feed, aquaculture feed, or converted to other products.
Carbon dioxide can be stored and sold for carbonated beverages, etc.
Corn cobs can be burned for heat or electricity generation.
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Appendix 1:
Preparing the malt:
You will need: Thermometer, stirring rod, distilled water, balance, sprouting process in a seed produces enzymes that will convert starch to sugar. This eliminates having to
add enzymes to the mash. About two weeks prior to the lab make a malt in which corn is sprouted to a length of about one inch. Soak corn seeds in a pail of warm water for 24 hours. Drain, add more warm water, and
drain again after 15 minutes. Spread the soaked seeds on a wet towel, cover with another wet towel and a plastic sheet (keeps towels moist). When sprouts reach a length of one inch, remove sprout and kernel from
towels and let dry. When malt is thoroughly dry, it can be ground for use in the mash.
Fermentation:
In anaerobic (no oxygen) conditions, yeast get energy from sugar by fermentation. In doing
so, they produce ethanol, carbon dioxide, and heat.
Preparing the yeast:
You will need: yeast, balance, warm distilled water, sugar, test tubes, test tube rack, thermometer, graduated cylinder.
Mix .5g of yeast with 20ml of warm (29C or 85F) water in a test tube, add a pinch of sugar and watch for bubbling to show yeast is active.
Procedure:
Divide the class into transportation groups such as these:
1.)Fossil (gasoline, diesel, methanol)
2.)Renewable (fermentation ethanol)
3.)Electric (mass transit, battery power)
4.)Solar vehicles
5.)Nuclear vehicles
6.)Wind Powered vehicles
Allow one class period for groups to research and list the advantages and disadvantages of their fuel source.
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