Yeast Fermentation Lab - MsJuo2011



BSCS Biology Energy Unit Name: _______________

Yeast Fermentation Lab

In this lab, we will use baker’s yeast, Saccharomyces cerevisiae, a single-celled fungus to examine the effects of temperature and nutrient levels on yeast metabolism and growth. Yeast perform a type of anaerobic cell respiration called alcoholic fermentation. Anaerobic respiration does not require oxygen.

We will mix yeast with table sugar (nutrient) in the bulb of a plastic pipette and observe the growth of the yeast culture over time. Growth will be measured by the height of the culture in the yeast pipette. We will examine the effects of temperature and the effects of nutrient availability on growth. Both variables can be considered limiting factors- remember what those are? You will work in a small group on a particular set of tubes and the results will be compiled as class data.

Before you begin, write one hypothesis about the effects of temperature and one hypothesis about the effects of nutrient availability on yeast growth.

Write rationales for each hypothesis on your individual student sheet.

Materials:

2 plastic pipettes with tips cut off per group 250 ml beakers

‘funnel’ pipette flask from ice bath or heated bath

‘skinny’ pipette thermometer

yeast dH2O in flask

table sugar (except for pipettes 1 and 2) electronic balance

ruler (mm) scoopula, weigh paper

Pipettes 1 and 2:

1. Weigh out 0.5 grams of yeast for each pipette. (You will not have any sugar – 0g sugar).

2. Use ‘funnel’ pipet to add 0.5 g yeast to each pipette.

3. Get a flask from the >34oC water bath that contains dH2O.

4. Using the ‘skinny’ pipette, add this warm dH2O to each pipette to fill the bulb. Gently release the dH2O into the bulb without touching the yeast; keep the bulb squeezed until you have removed the ‘skinny’ pipette.

5. Gently massage the pipette bulb until well mixed – don’t let the contents of the bulb go into the tube part!

6. Fill a small beaker with about 2 inches of water from the bottom of the >34oC water bath. Record the temperature of the beaker water.

7. Place your pipettes into the small beaker of warm water and record the starting time. Every 2 minutes, measure the height (mm) of the yeast culture and the temperature of the beaker water. Take at least 7 measurements.

Pipettes 3 and 4:

1. Weigh out 0.5 grams of yeast and 0.2 grams of sugar for each pipette.

2. Use ‘funnel’ pipet to add 0.5 g yeast and 0.2 g sugar to each pipette. Gently tap each pipette bulb to mix the yeast and sugar.

3. Get a flask from the >34oC water bath that contains dH2O.

4. Using the ‘skinny’ pipette, add this warm dH2O to each pipette to fill the bulb. Gently release the dH2O into the bulb without touching the yeast/sugar mix; keep the bulb squeezed until you have removed the ‘skinny’ pipette.

5. Gently massage the pipette bulb until well mixed – don’t let the contents of the bulb go into the tube part!

6. Fill a small beaker with about 2 inches of water from the >34oC water bath.

7. Place your pipettes into the small beaker of warm water and record the starting time. Every 2 minutes, measure the height (mm) of the yeast culture and the temperature of the beaker water. Take at least 7 measurements.

Pipettes 5 and 6:

1. Weigh out 0.5 grams of yeast and 0.5 grams of sugar for each pipette.

2. Use ‘funnel’ pipet to add 0.5 g yeast and 0.5 g sugar to each pipette. Gently tap each pipette bulb to mix the yeast and sugar.

3. Get a flask from the >34oC water bath that contains dH2O.

4. Using the ‘skinny’ pipette, add this warm dH2O to each pipette to fill the bulb. Gently release the dH2O into the bulb without touching the yeast/sugar mix; keep the bulb squeezed until you have removed the ‘skinny’ pipette.

5. Gently massage the pipette bulb until well mixed – don’t let the contents of the bulb go into the tube part!

6. Fill a small beaker with about 2 inches of water from the >34oC water bath.

7. Place your pipettes into the small beaker of warm water and record the starting time. Every 2 minutes, measure the height (mm) of the yeast culture and the temperature of the beaker water. Take at least 7 measurements.

Pipettes 7 and 8:

1. Weigh out 0.5 grams of yeast and 0.8 grams of sugar for each pipette.

2. Use ‘funnel’ pipet to add 0.5 g yeast and 0.8 g sugar to each pipette. Gently tap each pipette bulb to mix the yeast and sugar.

3. Get a flask from the >34oC water bath that contains dH2O.

4. Using the ‘skinny’ pipette, add this warm dH2O to each pipette to fill the bulb. Gently release the dH2O into the bulb without touching the yeast/sugar mix; keep the bulb squeezed until you have removed the ‘skinny’ pipette.

5. Gently massage the pipette bulb until well mixed – don’t let the contents of the bulb go into the tube part!

6. Fill a small beaker with about 2 inches of water from the >34oC water bath.

7. Place your pipettes into the small beaker of warm water and record the starting time. Every 2 minutes, measure the height (mm) of the yeast culture and the temperature of the beaker water. Take at least 7 measurements.

Pipettes 9 and 10:

1. Weigh out 0.5 grams of yeast and 0.2 grams of sugar for each pipette.

2. Use ‘funnel’ pipet to add 0.5 g yeast and 0.2 g sugar to each pipette. Gently tap each pipette bulb to mix the yeast and sugar.

3. Get a flask from the ice water bath that contains dH2O.

4. Using the ‘skinny’ pipette, add this ice dH2O to each pipette to fill the bulb. Gently release the dH2O into the bulb without touching the yeast/sugar mix; keep the bulb squeezed until you have removed the ‘skinny’ pipette.

5. Gently massage the pipette bulb until well mixed – don’t let the contents of the bulb go into the tube part!

6. Fill a small beaker with about 2 inches of water from the ice water bath.

7. Place your pipettes into the small beaker of room temperature water and record the starting time. Every 2 minutes, measure (mm) the height of the yeast culture and the temperature of the beaker water. Take at least 7 measurements.

YEAST FERMENTATION LAB

Student Sheet

Your Name _________________

Lab Partners’ Names ______________________________________________

Hypothesis: Effects of temperature.

Rationale:

Hypothesis: Effects of nutrient availability.

Rationale:

Results:

Fill out your data table during the lab. On the board, please write your start and end beaker temperatures and the averages for your two tubes over time.

Questions

1. Which pipettes served as the control for the nutrient availability procedure?

2. Which pipettes had:

a. the fastest growth?

b. the next fastest?

c. the slowest?

3. Based on your above answers, what conditions (nutrient and temperature) are best for yeast fermentation?

4. What were the substances in the bubbles?

5. If you were to graph a subset of your data to create a graph titled “The Effect of Nutrient Availability on the Rate of Yeast Fermentation”, what would be the:

a. Independent variable?

b. Dependent variable?

6. HONOR: Based on what you learned from the Enzyme Action Lab (liver and potato/ catalase and H2O2), what would you predict in terms of yeast fermentation if we had used boiling water (100oC)?

Results:

Table 1. Individual Data: Factor tested: ________________________

| |Beaker temp oC |Tube # ______ |Tube # ______ |AVERAGE |

|0 min | |0 mm |0 mm |0 mm |

|2 min | | | | |

|4 min | | | | |

|6 min | | | | |

|8 min | | | | |

|10 min | | | | |

|12 min | | | | |

|14 min | | | | |

|16 min | | | | |

|18 min | | | | |

Table 2. Class Data for Yeast Fermentation Rate

| |AVG for Tubes 1 & 2 (warm)|AVG for Tubes 3 & 4 (warm)|AVG for Tubes 5 & 6 (warm)|AVG for Tubes 7 & 8 (warm)|AVG for Tubes 9 & 10 (ice)|

| |(0.2 g sugar) |(0.5 g sugar) |(0.8 g sugar) |(0.8 g sugar) |(0.2 g sugar) |

|Start temp beaker |33 |34 |32.5 |30 |9 |

|oC | | | | | |

|End temp beaker oC| |30 |29 |28 |5.8 |

|0 min |0mm |0mm |0mm |0mm |0mm |

|2 min |0 |Overflowed (>70 mm) |2.5 |0 |0 |

|4 min |0 | |14 |0.5 |0 |

|6 min |0 | |32 |4 |0 |

|8 min |0 | |51 |10.5 |0 |

|10 min |1 | |65 |13 |0 |

|12 min |1 | |75 - overflow |16.5 |-0.5 |

|14 min |1.5 | | |26 | |

|16 min | | | |46.5 | |

|18 min | | | | | |

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