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| The Case: |
What Ails the Ale? (Brewmaster Blues) |
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Barry the Brewmaster was wiping down the counter after a lively Thursday evening at the Skyline Brewery, a popular brew-pub located in Atlanta. Just as he was getting ready to lock up, the owner of another microbrewery, Adam the Alemaker, strolls into Barry’s pub.
Adam announces, "Barry! I have a challenge for you. I propose a tasting competition next month, my Awesome Ale against your best brew. We’ll advertise all over town and sell $1 tickets. Anyone (over 21) will be able to taste the beers and vote, and the winner gets bragging rights to ‘The Best Beer in Atlanta’. What do you say?"
Barry replies, "Great idea, Adam, we’ll be ready!"
After Adam leaves, Barry goes to the kitchen and starts mixing up a new batch of his signature brew, Hunter Ale. He has already brewed one batch for his regular shipment, so he already has all the ingredients on hand. He mixes in the malt extract, containing the sugar, the hops for bitter flavor, pure spring water, and the yeast which mediates the fermentation reaction.
C6H12O6 + Saccharomyces cerevisiae = 2C2H5OH + 2CO2
(glucose plus yeast yields ethyl alcohol and carbon dioxide)
Saccharomyces cerevisiae
Unfortunately, within a few days, Barry notices that in his new batch, the yeast don’t appear to be growing in one fermenter, and no gas is being produced. With the title of ‘Best Beer in Atlanta’ or his regular monthly profits at stake, Barry must determine what is wrong with the new brew batch. He removes a sample from the fermenters holding new batch and the old one, and takes them to the local university for analysis.
Case Author:
Cindy Giver Emory University:Center for Science Education
Rob Pyatt Emory University:Center for Science Education
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Case Analysis
Students will use problem-solving skill and cell biology lab techniques to examine yeast cultures provided by the instructors.
The laboratory class will introduce yeast growth kinetic analysis methods, and students will ask the questions:
Are the yeast alive?
Are the yeast growing at normal rates?
Are there appropriate levels of glucose in the fermenter to support yeast growth?
What do you know?
Lay information about beer, yeast, and fermentation.
Light microscopy
Information search and retrieval methods
What do you need to know?
Laboratory skills and procedures used in this assignment.
How to write up a clear and concise laboratory report.
Basic yeast biology
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Option: Include a know / need to know chart like the one below:
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What do you know?
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What do you need to know?
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Learning Goals
Goal(s)
Experimental design, use of scientific methods and importance of controls.
Development of problem-solving skills and logical reasoning.
Familiarization with basic laboratory procedures. The students will have little or no prior laboratory experience, and need to become comfortable with working in this setting.
Develop skills working with: Cell counts using a hemacytometer and spectrophotometer, growth kinetic assays, and glucose oxidase assay.
Working in groups, proper note-taking and laboratory reporting skills.
• The students will learn the importance of metal ions in living organisms.
• The students will learn that we can use chelating reagents to effectively remove metal ions in solution.
• The students will be able to understand the chemistry (structure and function) of chelating reagents.
• The students will be able to learn the thermodynamics of metal-ligand complexation.
• The students will be able to do titration experiments to determine quantitatively the amount of divalent metal ions in solution.
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Standards
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Investigations and Activities
Before class, read the introductory information accompanying the lab manual, and find one additional source (textbook, webpage, or scientific literature) covering basic yeast biology.
At the beginning of the lab session, the case will be introduced and students (with instructor guidance) will brainstorm about potential problems affecting the yeast growth. This will take the form of a group meeting, where students will be able to present the information that they have found, and discuss how it applies to the problem at hand.
Lab techniques that will be introduce include: cell counts using a hemacytometer and development of a standard absorbance curve, some culture sampling, growth kinetics analysis, glucose oxidase assay to determine the sugar content of the media.
Students will analyze their data to deduce the problem affecting yeast growth in their experimental sample. This will vary between working groups (dead yeast, growth-compromised yeast, or low glucose).
Returning home after World War I, American soldiers express their dissent over Prohibition. By their absence, they were denied the opportunity to vote on the issue.
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Resources
The necessary lab procedures are described in the laboratory text. The case described here is a modification of a basic yeast growth kinetics lab.
Experimental Cell & Molecular Biology, Second Edition, by John S. Choinski, Jr. WCB/McGraw-Hill Companies, Inc. 1992
The case described here is a modification of a basic yeast growth kinetics lab found in chapter 5 of the text.
Additional sources of information:
Website describing counting of yeast cells using a hemacytometer
http://www.math.usu.edu/~powell/ysa-html/node20.html
and the glucose oxidase assay
http://www.math.usu.edu/~powell/ysa-html/node19.html
very nice description of general hemacytometer use with good graphics to aid understanding of the exquipment
http://www.ruf.rice.edu/~bioslabs/methods/microscopy/cellcounting.html
growth curve determinations
http://www.bio.davidson.edu/courses/genomics/method/growthcurves.html
Primary reference for glucose oxidase determinations
Bergmeyer, H.U. and Bernt, E., Methods of Enzymatic Analysis 2nd ed., (1974), 1205-1212
Interesting information on beer making and some history
http://www.history-of-beer.com/
http://www.realbeer.com/
Students will usually obtain additional references or resources
to help answer or explore their questions. |
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Special Data Items
1. yeast.gif
2. prohib5.jpg
3. ale.gif
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Student Products
1. Information retrieved by students on basic yeast biology.
2. Lab notebook writeup, with description of the problem, methods, results and conclusions.
3. One group of students will prepare a poster describing the case, their results and conclusions. The report will be presented at a poster session to be held at the end of the semester, along with other student presentations.
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Assessment and Evaluation Plan
Assessment will be based primarily on the students’ individual lab notebook writeup. The overall grade for the lab exercise will also incorporate satisfactory demonstration of information retrieval, their participation in the working groups, use and understanding of the equipment and procedures, and class discussion. Poster presentations will be assessed separately at the poster session.
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Implementation
This case will be used as one of the first laboratory exercises in a new lab section for an upper-division cell and molecular biology course.
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Course name:
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794 Cell and Molecular Biology
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Likely sequence in
syllabus:
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Early laboratory exercise
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Time during term:
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Duration:
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2 days
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Setting:
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lab
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Students in course:
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Collaborative elements:
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Students are expected to work in groups and share resources and results
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Additional notes:
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Credits
Beer picture
http://realbeer.com/spencer/amber-ale.html
Picture of yeast
http://www.barrelhouse.com/yeast.html
We Want Beer prohibition era picture
http://www.beerhistory.com/gallery/holdings/prohib5.shtml
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