TOP 3 CO2-production. Which type of yeast is the best?
Groot, E. & Schreurs, L.
RSG Enkhuizen, The Netherlands
April 14, 2010
Summary
Will there be a difference in production of CO2 and ethanol when different types of yeast are
solved in a glucose solution? By a temperature of 25 degrees and a same amount of glucose
solution, we looked at the CO2 production by using three different types of yeasts.
Introduction
In connection to the article ‘Yeast and
fermentation: the optimal temperature’, a
couple of schools got the opportunity to
take part in the fermentation project.
Groups of two pupils have to set an inquiry
of their own, and accomplish this.
In the future oil resources will be
exhausted. For this we will have to find
solutions.
This leads to worlds oldest chemical
process: the production of bio-ethanol from
sugars by fermentation. Fermentation is the
process where glucose is converted by
yeast cells into ethanol and carbon dioxide.
A fast and large production is significant.
C6H12O6 (s)  2 CO2 (g) + 2 C2H5OH (l)
We are interested to look at the production
of carbon dioxide and ethanol in an amount
of time when we use different kinds of
yeast. We are going to use baker´s yeast,
fresh yeast, and yeast that is used for the
production of beer.
We think the production of CO2 by using
baker's yeast or fresh yeast will be larger
than the yeast which is used to produce
beer.
 Figure 1: Glucose
Materials
 Yeast type 1,
dried baker’s
yeast (7 grams)
 Yeast type 2,
Saccharomyces
cerevisiac Siccum
(7 grams)
 Yeast type 3,
fresh yeast
(7 grams)
 3 Spatulas
 1 M Glucose
solution
 Demineralized
water
 Thermostat
 0,25 L Erlenmeyer
flask
 100 mL Measuring
glass
 2 0,8 L Beakers
 Leading hose
 Stopwatch
 Weighing machine
 Gas burner
 Figure 2: the
installation for the inquiry
Experimental procedure and
research
The first step was to built the installation
according to the picture. After this step a 1
M glucose solution had to be made. This
could be made by combining water with
the right quantity of glucose. For the whole
inquiry 0,5 L glucose solution is necessary.
After the glucose solution has been made,
it has to heat up till the solution gets a
constant temperature of 35 degrees
Celsius.
The second step is to add 7 grams of
yeast type 1 in a 0,25 L Erlenmeyer flask,
after which we fill the Erlenmeyer flask
with glucose solution till the flask is filled
up to 0,125 L solution. The first
measurement can start.
After 10 minutes read off how many
carbon dioxide has been produced in the
measuring glass. Repeat this measurement
and read off how many carbon dioxide has
been produced after 15 minutes. When this
measurement is done, repeat it with yeast
type 2 and type 3.
Results
The glucose had a mass of 180,16 M, so
we weighted 90,08 grams of glucose on the
weighing machine. When we poured cold
water in a 0,8 L Beaker, we noticed that
the glucose did not dissolved, but became
hard. To solve this problem, we heated it
up until the glucose was totally dissolved
in the water. This took a few minutes.
When the glucose solution was ready it had
a clearly white color, almost colorless.
Because the glucose solution was still hot,
we had to wait until the glucose solution
had a temperature of 35 degrees Celsius.
We added 7 grams of dried baker’s yeast
(which was already weighted and packed
in a little packet, looking brown and
grained) in the 0,25 L Erlenmeyer flask
and we filled the Erlenmeyer flask up to
0,125 L solution (with the glucose
solution), we noticed that the solution
became dulled and a bit brown of color.
We started the stopwatch and after 4
minutes CO2 was already produced. We
also noticed that at the top of the solution a
sort of foam appeared, which became
thicker and thicker until the inquiry
stopped. After 10 minutes, we measured
that 68 mL of CO2, and after 15 minutes
around 125 mL of CO2 was produced. The
125 mL is an estimate, because we used a
100 mL measuring glass.
We repeated this inquiry with yeast
that is used for the production of beer. The
yeast itself looked as yellow powder, and
together with the glucose solution it
became a dull and dark yellow solution. In
this experiment there was almost no
production of CO2, because we didn’t
notice generation of gas. Although we
didn’t really noticed generation of gas, we
did measure that after 15 minutes the same
quantity of CO2 was produced as after 10
minutes, namely 6 mL of CO2.
The third experiment was with fresh
yeast. This yeast had a beige color and was
packed cubical in paper. We had to scrape
7 grams of it before we poured it in the
Erlenmeyer flask, because it wasn’t
powder but more a bit hard and
calciferous. Together with the glucose
solution, the solution had a dull and
slightly white-brown color (a bit milky).
 Figure 3: The measurements
of
the production of CO2 (in ml) for
each type of yeast.
We noticed the generation of gas started
after 7 minutes. After 10 minutes 7 mL of
CO2, and after 15 minutes 17 mL of CO2
was produced. We also noticed a tin lay of
foam. The results are presented in the
histogram below. The photo’s are
presented as well.
Time
Baker´s yeast
Yeast (for beer)
Fresh yeast
10 minutes
15 minutes
 Table
1: Photo’s of each type of yeast after 10 and 15 minutes.
We also calculated the reaction speed for
each inquiry with yeasts. The results
are presented in the tables below.
Baker’s yeast
Time
We putted the results also in a graph, to
show the connection between the reaction
speed and time.
Quantity
Reaction speed=
10 minutes
68
15 minutes
125
Table 2: The reaction speed of the CO2 that was produced with baker’s yeast calculated after 10 and 15 minutes
Yeast for the
production of
beer
Time
Quantity
Reaction speed=
10 minutes
6
15 minutes
6
Table 3: The reaction speed of the CO2 that was produced with yeast (for beer) calculated after 10 and 15 minutes
Fresh yeast
Time
Quantity
Reaction speed=
10 minutes
7
15 minutes
17
Table 4: The reaction speed of the CO2 that was produced with fresh yeast calculated after 10 and 15 minutes
are presented in the tables below, and also
presented in the histogram on the next
page.
Figure 4: The reaction speed (ml/s) versus the time (s) measured after 10,15 and between 15 minutes
for each type of yeast dissolved in the glucose solution.
Conclusion and discussion
Evaluation
The main purpose of this inquiry was to
show whether there is a difference in
production and reaction speed of CO2 and
ethanol when different types of yeast are
solved in a glucose solution.
According to this inquiry there is a
difference indeed. As is shown in Figure 3,
dried baker´s yeast produces the most CO2
in mL, at least more than the other types of
yeast. Dried baker´s yeast is especially
used as raising agent for the making of
bread. Its production of CO2 is significant
to let the bread raise. The production of
ethanol is not necessary. It has a useful
design and it dissolves perfect. This makes
it easier to produce CO2 because the
production of CO2 can start immediately
after the baker´s yeast has dissolved in the
glucose solution.
…….
Fresh yeast however, is also used for
the making of bread. But because its
design isn´t as handy as dried baker´s
yeast, it doesn´t dissolve as quickly as
baker´s yeast and so the production of CO2
doesn´t start as quickly as baker´s yeast.
As the same as fresh yeast, the yeast
that is used for the production of beer
doesn´t also produce as many CO2 as
baker´s yeast. As is shown in Figure 4 and
Table 3 there wasn’t any reaction speed
after about 10 minutes. This means after 10
minutes there wasn't any production of
CO2 anymore. Under other circumstances
(for example another time trail,
temperature) the results of the CO2
production could be different.
The reaction speed differs because each
type of yeast got its own optimal
conditions. For all the inquiries we used
the same conditions, and only changed the
types of yeast.
We started with the inquiry question “Will
there be a difference in the production of
CO2 by using several types of yeast?”.
Later, we increased our inquiry question by
also investigating the reaction speed.
During the inquiry itself, we didn’t came
into big trouble. We did decide not only to
measure the production of CO2 after 10
minutes, but also after 15 minutes. This
was a useful decision. The inquiry did
became difficult, when there was more
CO2 produced than the measuring glass
could carry. So next time we could
measure after another time trail and with a
bigger measuring glass.
Another inquiry question could be;
“Will there be a difference in CO2production, when different amounts of
yeast are being used?”
Bibliography
 Picture installation inquiry,
http://www.thuisexperimenteren.nl/science
/vergisting/gasval.gif
 Slaa, J., Gnode, M. & Else, H. (2009).
Yeast and fermentation: the optimal
temperature
 Reaction speed, Wikipedia® (2009).
http://nl.wikipedia.org/wiki/Kinetiek
 Reaction speed, Binas havo/vwo 37A,
©Wolters-Noordhoff bv
Groningen/Houten (2004), The
Netherlands
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