Fermentation: the (un)converted sugar
Koomen, L. Pluut, K.
Gymnasium Felisenum, The Netherlands
Summary
Fermentation, as one of the oldest chemical processes, is an important way of winning
bio-ethanol out of sugars. So finding the best way to produce bio-ethanol is very useful.
The oil sources just cannot bear the amount of oil we use. Bio-ethanol is a possible
solution, and therefore a reason to take a closer look at it. What we have been trying , is
finding the best possible sugar for fermentation. Does granulated sugar, caster sugar or
starch work out best? The fermentation process, which of course is going to be
explained in the following paragraph(s), was being measured by the release of carbon
dioxide. These measurements resulted in glucose as the best working sugar, which
didn’t surprise us. Unfortunately, the amount of carbon dioxide was not realistic. That
was no surprise, because, for example, the temperature was not even close to the
optimal circumstances and our measurements not as accurate as should.
Introduction
place: C6H12O6 (s) ---> 2CH3CH2OH
In the introduction we will try to explain
(l ) + 2CO2 ( g ). C6H12O6 is one of
what we expect of our fermentation
the sugars that can be formed out of
project and explain how fermentation
starch.
works.
Fermentation would not be possible
What we expect to be the best
without sugars. So the first question is,
working sugar is: glucose. The other
how do you get sugars? Sugars are
sugar we used, sucrose
extracted out of starch or for example
(C12H22O11), is, also because of
potatoes. For our experiment we used
hydrolysis, converted into glucose
starch and therefore we will explain
and fructose.
how to get sugars from starch. Starch
So basically our sugars are sorted as
[(C6H10O5)n] can be converted into
followed:
sugars, for example glucose because of

Glucose: The
hydrolysis. In this process, an H2O
sugar which is directly available
molecule breaks the long carbon chain
for fermentation.
on some points and thereby forms

Sucrose: The
sugars. In our experiment we also used
sugar that, at first must be
unconverted starch, but we do not
converted into glucose because
expect it to result in a big amount of
of hydrolysis.
carbon dioxide.

Starch: the basic
Now we know how to get the sugars,
of sugars; a huge molecule that
we can use the sugars for the
also must be converted into
fermentation. In the actual
glucose by hydrolysis.
fermentation process, the sugars are
converted into (bio-)ethanol and
So it is logic, that we think glucose
CO2. The following reaction takes
works out best, because it’s
already able to be used for
fermentation. The other 2 sugars
need time to get converted into
sugars and will be used for
fermentation later than glucose.
For fermentation you also need
yeast. We used baker’s yeast for
all the 3 sugars. So the baker’s
yeast is an control variable.
Methods and Materials
We firstly weighted 6 empty 0,5L water
bottles without the cap. We then filled
the bottles with 250,0 ml of regular
water. We then weighted the 3 different
saccharides: glucose, soft brown sugar
and starch. We weighted 2 times 40,0
gram of each saccharides. We then filled
the bottles with each one a portion of
40,0 gram of the saccharides, so we got
6 bottles filled with or glucose or soft
brown sugar or starch. While doing this
we labeled every bottle with the
saccharides they had in. We then added
1,0 gram of baker’s yeast, S. cerevisiae,
to every bottle. Immediately after that
we put a water cup at each bottle. After
some careful shaking we put the bottles
in a rack. Every 3 days we shaked the
bottles carefully. After 1 week we
shaked for the last time so that all the
compressed C02 could escape. Then we
took the water cups off and weight
every bottle with their suspension as
soon as possible. Because we had 2
bottles for every saccharides we could
measure 2 masses differences so that
we could make an average. For every
saccharides the mass difference was
determined and with that also the
released CO2 gas.
Results:
We measured all bottles with their
suspension without the water cap after
1 week. The mass difference was the
released CO2. We then made an
average with their deviations for each
type of saccharides. Table 1 presents all
those values.
Type
saccharide
Mass CO2(g)
Averaged
Mass CO2(g)
glucose
5,05
5,09
5,07±0,02
starch
3,70
3,06
3,38±0,32
Soft brown
sugar
3,62
4,38
4,00±0,38
Table 1: Release of CO2 and averaged
release CO2 for each type of
saccharides.
The average values of each soft brown
sugar, starch and dextrose could be put
in a graph. Graph 1 shows us the
difference more illustrated.
Graph 1: Average CO2 release of each
type saccharides.
Conclusion and discussion
As you can see glucose does release the
most CO2 of the three saccharides. Soft
brown sugar and starch give us
respectively 21% and 33% less CO2 than
soft brown sugar.
As you can see in the introduction, the
following chemical reaction that
took place is: C6H12O6 (s) 
2CH3CH2OH (l ) + 2CO2 ( g ). The
amount of moles co2 that is
produced is the same amount of
moles ethanol. To find out how
much ethanol we had produced, we
had to know the mol mass of either
ethanol and carbon dioxide. CO2
weights 44,01 g/mol and ethanol
46,0688 g/mol. We had 5,07 g CO2.
5,07/44,01=0,115 mol. 0,115 mol .
46,0688 g/mol =5,31 g ethanol.
As you can see there was a mass
difference after the fermentation what
indicates there was a production of
CO2. All cultures had a significant
amount of CO2 produced with glucose
the most producing. As our hypothesis
showed, the unconverted sugars, starch
and soft brown sugar, are less effective
than glucose. Furthermore you can see
that against popular belief starch still
work out in the fermentation process.
The production was indeed less but not
much less; only 33% less production.
This is a lot if you mind that starch is
much easier to obtain. So the efficiency
of fermentation is not that high. What
starts of as corn or perhaps potatoes,
results in a kind of lsmall amount of
carbon dioxide and thereby a small
amount of bio-ehtanol. Of course our
conclusion could have been better. We
were not able to check all of the control
variables. The temperature, which
should have been 37 degrees, wasn’t
that high in our experiment.
Bibliography
1. www.wikipedia.nl
2. yeast and fermentation: the
optimal temperature, by Slaa, J.
Gnode, M. and Else, H.
3. Chemie Overal vwo deel 2