The fermentation of sugar: Which sugar is the best?
Summary
Fermentation, it’s an important subject in
recent studies for new ways of
transportation. In the search of new cleaner
energy source, bio-ethanol is one of the
possibilities for a new cleaner fuel to be
used in transportation, and to produce bio
ethanol, you need a fermentation process.
In fermentation processes there are
different factors, or variables, which can be
varied in order to get the best results in
producing bio-ethanol.
So we asked ourselves if we couldn’t
change the type of sugar to produce
ethanol more efficiently. We followed the
fermentation process with 4 types of sugars
namely dextrose, fructose, granulated
sugar and cane sugar. We measured the
loss of mass, which a bottle experience
because CO2 gas was produced. The result
of our experiment concluded that cane
sugar is the most efficient way to produce
bio-ethanol. Since we only tested 4 types
of sugar this also poses the question of
finding an even more efficient sugar to
produce ethanol.
Introduction
To measure how good the
fermentation process is, you can
directly measure the amount of
ethanol produced, which is the
most straightforward way, but a
more often used method is
measuring how much CO2 is
produced in the process. This is
a perfectly viable method,
because in every fermentation
process an equal amount of CO2
is produced compared to the
amount of ethanol produced.
The natural process of
producing sugar is called
photosynthesis, namely:
6 CO2 (g) + 6 H2O (g/l)
C6H12O6(s) + 6 O2 (g)
This is an endothermic reaction that can
only take place under the influence of
sunlight.
After the sugar is produced, yeast cells can
ferment glucose without oxygen or
sunlight, using the following reaction:
C6H12O6(s)  2CH3CH2OH (l) + 2CO2 (g)
The purpose of fermentation is to make
that sugar into a fluid which can be used as
a fuel for transportation.
In our experiment we tested the different
types of sugar available in your local
supermarket, which in our case are
Dextrose, Fructose, cane sugar and
granulated sugar. And our hypothesis is
that dextrose and Fructose, which are both
monosaccharides, will be the best sugars to
be used in the fermentation process,
because disaccharides need to be
hydrolyzed first, before they can be
fermented, which costs time and energy
and thus will make the process less
efficient. The goal of our experiment was,
as we mentioned in the summary to find
out which sugar is the most efficient in
producing ethanol.
In our experiment we decided to not only
do our measurements in grams, but keep
the calculations in grams as much as
possible, because in production
environments this is much more important.
Control variables in our experiment
include, but are not limited to:
Temperature, air pressure, water pH,
amount of sugar, amount of yeast and the
type of bottle used.
Experimental procedure and
approach
weighed the bottles before the 2 weeks
were over to check on the process and if
the experiment was going properly, this
however wasn’t relevant for the hypothesis
we were trying to prove.
After the 2 weeks we reweighed the bottles
and calculated the loss of mass they
experienced, which also was the mass of
the CO2 gas that was produced. After this
we put it in table 1 to compare the
differences between the 4 sugars. The
measurements of the 2 series were
averaged and put into a graph as you can
see in figure 1. Finally we made table 2 in
which we put the calculated average
production of ethanol and the amount of
ethanol produced per gram of sugar.
weight in gram
We started with getting 45 grams of each
Results
sugar twice and also 1 gram of yeast per
Before measuring we opened the bottles to
bottle (8 bottles). We did the experiment
let out the CO2 gas, because we wanted to
twice to get more accurate results and rule
know the remaining weight of the bottle
out any small mistakes and/or faults in our
without the CO2 gas. Before doing this we
procedure that would otherwise tamper
also confirmed that there were bubbles
with our results.
escaping from the airlock.
After getting 8 bottles of 0.5 L we started
We made table 1, which includes the
to fill them with 45 grams of sugar and 1
weight that was lost from the bottle and
gram of yeast each until we had 2 bottles
was released in the air as CO2 gas. We can
filled with dextrose, 2 bottles filled with
assume that all the mass that was lost has
fructose, 2 bottles filled with granulated
been converted into CO2 gas.
sugar and 2 bottles filled with cane sugar.
After this we labelled
average difference in weight between start and end of the
them to indicate which
sugar they contained and
experiment
which series it was.
The labelled bottles were
25
filled up to 250 ml of tap
water. Each bottle that was
20
filled with the water was
shaken for a minute, after
15
which we placed the
airlocks on top of the
10
bottles so the CO2 gas
could escape but the
5
mixture isn’t exposed to
the open air. Drawing 1
0
shows how the experiment
dextrose
fructose
granulated sugar
cane sugar
looked. Then we weighed
the mass of each bottle and
Figure 1. This shows the average release of
wrote it down. We then left them to let the
CO2 gas versus the four different sugars.
fermentation process do its work. We also
Reeks1
Sugar used
Weight
difference
(g)
(serie 1)
Weight
difference
(g)
(serie 2)
Difference
between serie
1 and serie 2
(g)
Dextrose 21
20
1
Fructose
20
17
3
Granulated 24
21
3
sugar
Cane
23
23
0
sugar
Table 1: the masses of CO2 gas that have
been released, the difference between the
two series and the average weight of the
CO2 gas that is released.
Data analysis
We presented the averaged loss of mass by
the release of CO2 gas. We’ll calculate the
amount of ethanol produced by finding out
how much mol CO2 gas has been produced
and find out which sugar produces ethanol
the most efficient. To make the values
more comprehensible we have put them in
table 2. To calculate the amount of ethanol
produced we used the reaction:
C6H12O6 → 2C2H5OH + 2CO2 for dextrose
and fructose.
C12H22O11 + H2O→ 4C2H5OH + 4CO2 for
granulated sugar and can sugar
(sacharose). With the reaction formula
we can calculate the amount of ethanol if
we know the amount of CO2 produced. As
you can see the relation between CO2 and
ethanol are the same with both the
monosaccharide and disaccharide namely 1
ethanol molecule for every CO2 molecule
produced.
For Dextrose the calculation was:
20.5g/44.01u = 0.466 mol CO2 which
means 0.466 mol ethanol. To convert this
figure into gram 0.466 mol * 46.068u=
21.45 gram ethanol. This has been done for
every sugar and put into the table.
We added 45 grams of every sugar so we
can also calculate the amount of ethanol
produced per gram sugar.
Average
weight
difference
(g)
20.5
18.5
Dextrose
22.5
fructose
23 Granulated
sugar
Cane sugar
Average
weight of
CO2
produced by
the
fermentation
(g)
Average
weight of
ethanol
produced
(g)
Ethanol
produce
d per
gram
sugar
(g)
20.5
18.5
22.5
21.5
19.4
23.6
0.48
0.41
0.50
23
24.1
0.51
Table 2: the average weight of CO2
produced with the weight of ethanol
produced to show how efficient each sugar
is in producing ethanol by fermentation.
Conclusion and discussion
By confirming that bubbles were escaping
from the airlock and the loss of weight of
the bottle it’s certain that CO2 gas was
produced by the yeast.
If you look at table 2 you can see that
disaccharides clearly produce more ethanol
than the monosaccharides. The
disaccharides produce on average about
20% more ethanol than the
monosaccharides, which is a substantial
amount more.
In our experiment we encountered several
problems which ultimately led to what
became our odd results. At first there
wasn’t enough yeast, so we had to wait a
day for our second serie to start, but this
shouldn’t have affected our results.
Another thing we had a problem with was
that at first we only had 3 sugars, because
the fructose was delayed, so we actually
had 3 different times at which we started
our experiment. This shouldn’t matter
either, because we were only looking for
the total amount of CO2 produced, and not
how fast that would happen. Even though
the things that went wrong shouldn’t have
affected our results, something clearly
went wrong, as disaccharides should
normally be less effective as
monosacharides because disaccharides first
need to be hydrolyzed before they can be
used in the rest of the chemical process.
It could also just be that our hypothesis
was wrong and the fact that you simply
have different amounts mol of sugar in the
same amount of gram with the
disaccharides and the monosaccharides can
convert faster but don’t have enough mol
sugar to be more efficient than the
disaccharides and therefore our experiment
showed that the disaccharides were more
efficient.
Perhaps there were other factors/control
variables in the experiment which we have
overlooked, but greatly affect the
experiment, possibilities are that the
products produced in the chemical process
are actually slowing the yeast down or
even killing it, like ethanol or the CO2 or
maybe we need to monitor the pH of all the
solutions because one sugar/yeast
combination produces more acid than the
other.