The Fermentation of Yeast
Phyllings Lerisson
Chipola Junior
College
CHM 2210
Introduction
Fermentation is used to make bread and wine. The
process of fermentation converts glucose into ethanol and
carbon dioxide. In 1810, Gay Lussac discovered the general
chemical equation for the breakdown of sugar into ethanol and
carbon dioxide: C6H12O6---- 2CH3CH2OH + 2CO2
A chemist by the name of Louis Pasteur discovered that
when a combination of spicific salts were incorporated into the
process of fermentation, the reaction proceeds at a faster rate;
this combination of salts became known as Pasteur’s salts.
Pasteur’s salts solution consists of 2.0g potassium phosphate,
.2g calcium phosphate, .2g magnesium sulfate, and 10g
ammonium tartrate in 860 mL of water.
Gay Lussac
Louis Pasteur
Discovered the general
equation for the process
of fermentation.
Discovered
a
combination of salts that
allowed fermentation to
proceed at a faster rate;
these salts are named for
Purpose
The purpose of the experiment is to measure
the rate at which the fermentation occurs. The rate
can be determined by measuring the amount of
carbon dioxide that is present. A carbon dioxide
gas sensor and graphing calculator will be used to
record the levels of carbon dioxide that result from
this experiment. The prediction is made that the
presence of Pasteur’s salts will increase the rate of
carbon dioxide production.
Materials
1 package of yeast
Graphing calculator
Glucose solution
CBL
Pasteur’s salts
CO2 Gas sensor
Distilled water
Graduated cylinders
Pipettes
Plastic bottle
Procedure
1. Connect calculator and C B L . Push APPS. Select CO2 gas
sensor.
2. Select DATA MATE. Change mode of calculator to TIME
GRAPH.
3. Pipette 2mL of distilled H2O and 2mL of glucose solution into a
graduated cylinder. (Use separate pipettes for each solution.)
4. Carefully weigh out .05g of dry yeast and put into plastic bottle.
To the yeast, add the glucose and distilled H2O.
5. Stopper the bottle with the CO2 gas sensor. Press start on the
calculator. When graph is complete, manually record data.
Data
The Amount of Carbon Dioxide Present in the Fermentation of
.05g Yeast
RUN 1
4000
Amount of Carbon Dioxide Present
(ppm))
3500
3000
2500
w/ 2mL Pasteur Salts
w/ 2ml Water
2000
1500
1000
500
0
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34
Time Elapsed (in minutes)
Data
The Amount of Carbon Dioxide Present in the Fermentation of .05g
Yeast
RUN 2
Amount of Carbon Dioxide Present (ppm)
6000
5000
4000
w/ 2mL Pasteur Salts
3000
w/ 2mL Water
2000
1000
0
0
2
4
6
8 10 12 14 16 18 20 22 24 26 28 30 32 34
Time Elapsed (in minutes)
Conclusion
In both Run 1 and Run 2, the rate of carbon dioxide production was calculated at 18
minutes:
Run 1
When Pasteur’s salts were added to the fermentation process, the carbon dioxide had a
production rate of 88.5ppm/min; without the addition of Pasteur’s salts, carbon dioxide
had a production rate of only 41.3ppm/min.
Run2
When Pasteur’s salts were added to the fermentation process, the carbon dioxide had a
production rate of 79.8ppm/min; without the addition of Pasteur’s salts, carbon dioxide
had a production rate of 58.7ppm/min.
Based on the average results of this experiment, the rate of carbon dioxide production
when Pasteur’s salts are present is 1.68 times faster than when Pasteur’s salts are not
present.
The hypothesis—stated in Purpose—is supported; the addition of Pasteur’s salts does
increase the rate of carbon dioxide production.
*The levels of Carbon Dioxide
Present (ppm) in each Run
RUN 1
RUN 2
Time W/Salts W/H2O
W/H2O
W/Salts
0
841
635
577
508
2
997
704
811
645
4
1124
753
880
684
6
1310
821
958
733
8
1437
860
1036
831
10
1613
929
1153
909
12
1857
1017
1290
1056
14
2141
1114
1496
1212
16
2297
1251
1730
1378
18
2434
1378
2014
1564
Notice, that at time zero (0), the
values do not start out at zero.
The values do not start out at
zero because carbon dioxide is
naturally present in the air.
Since the experiment could not
be carried out inside of a
vacuum, carbon dioxide is
already present when the
experiment first begins.
*Only a portion of the spreadsheet is presented.