Fermentation of various types of sugar by benbenzhou


									Fermentation of various types of sugar

                     Maaike van Berkel en Lucie van Diggelen
                         Gymnasium Haganum, 5SCHK
                                 12 april 2010
At the moment there is a strong need for bio-ethanol, because the stocks of fossil fuels are
running out. Also the earth is polluted by all used chemical fuels and their emissions of
noxious gasses. One of those noxious gasses is CO2. Due to the high percentage of CO2 in the
atmosphere the greenhouse effect is further stimulated. That is very harmful for nature and
eventually for the human being. Bio-ethanol is made by the fermentation of sugar. It will not
cause a disruption of the carbon cycle, because the CO2 that will appear, is the same as the
CO2 that the plant wherefrom sugar is made, has removed from the air for the

Some sugars ferment by an addition of yeast. Fermentation in an anaerobe situation causes
CO2 and ethanol. The yeast cells will die when concentration of ethanol is too high for them.
Most yeast cells die when the concentration of ethanol reaches 14%.

This inquiry will examine how much CO2 and so how much bio-ethanol will arise by the
fermentation of three various sugars. These three sugars are D-glucose, D-fructose and
sucrose. For these three sugars is chosen because they are easy to obtain.
By an addition of yeast, D-glucose reacts with the yeast to ethanol and CO2. First it changes
into D-fructose, then it will ferment. In molecular formulas this
reaction is:

C6H12O6 (s) → 2 CH3CH2OH (l) + 2 CO2 (g)

The structure formula of D-glucose is:

                                                           Figure 1: the structure of D-glucose

Apart from D-glucose there exists D-fructose. The molecular formula of D-fructose is also
C6H12O6, but the structure formula is different. The reaction from D-fructose with the yeast is
in molecular formulas the same as the reaction from D-glucose. The structure formula of D-
fructose is:

Figure 2: the structure of D-fructose

Sucrose (C12H22O11) is a sugar build of a D-fructose molecule and a D-glucose molecule. It is a
disaccharide. Before it can ferment it has to be hydrolyzed by an enzyme in yeast. Sucrose
splits into D-fructose and D-glucose. These two molecules will ferment through the yeast.
This reaction in molecular formulas is:

C12H22O11 (l) + H2O (l) →2 C6H12O6 (l)

2 C6H12O6→ 4 CH3CH2OH (l) + 4 CO2 (g)

The structure formula of sucrose is:

Figure 3: the structure of sucrose

                                                   Scale with two decimals
Inquiry question                                   9 test tubes with a diameter of 3 cm
Which type of sugar, D-glucose, D-fructose or      3 small corks with a small tube
sucrose, will cause the largest production of      Distilled water
CO2 and so the most bio-ethanol by                 Jar
fermentation under the same circumstances?         Measuring cylinder (200 mL)
                                                   Permanent marker
                                                   20,1 grams solid sucrose (white sugar;
The expectation is that there will be no big       crystals)
differences in the quantities of CO2 and so of     20,1 grams solid D-D-glucose (white powder)
bio-ethanol, because the mass is held              20,1 grams solid D-fructose (yellow/white
constant so that each solution will contain an     crystals)
even amount of carbon atoms. If there is a         3 pipettes (25 mL)
sugar the yeast likes the best, that will be the   3 small flasks (100mL)
sugar that produces the most bio-ethanol by
                                                   Experimental Procedure
fermentation. Probably glucose and fructose
will cause the largest production of bio-
                                                   Before you start the experiment make three
ethanol because sucrose has to be hydrolyzed.
                                                   flasks of 100mL with sugar-solutions. The first
Materials                                          with 100mL distilled water and 6,7 grams solid
                                                   sucrose, the second with 100mL distilled
9 plastic 0,5 L bottles                            water and 6,7 grams solid D-fructose and the
2,25 grams S. Cerevisiae cells (baker’s yeast)     third with 100mL and 6,7 grams solid D-
A large bowl filled with water at a constant       glucose. Fill the flasks first for a quart and
temperature of 33˚C                                shake them till all sugar is dissolved. Fill them

off with distilled water till the line on the flask
so you have 100,0 mL of each sugar solution.

Rinse each of the three pipettes three times.
Use one pipette for one solution. Write on
the pipettes which sugar has been in it, so the
next time you do this experiment you can use
the same rinsed pipettes. Pipette 25 mL of
each solution and put this in three different
test tubes. Add 0,25 grams of yeast to each
test tube. Cork the test tubes up properly with
corks with a small tube in it. Mark each test
tube with sucrose, D-fructose or D-glucose,
according to the substance that is in it. Put         Figure 4: The testing set-up

three bottles upside down in a jar that is filled
with water at room temperature (20˚C) so
that each bottle is completely filled with
water. Shake the three test tubes at the same
time for 10 seconds. Lead the tubes in the
bottles, one tube per bottle. Place the test
tubes in the hot water bath that already is
heated to 33˚C. Make sure that the                    Results
temperature is constant and leave this setting
for 48 hours.                                         Table 1: The production of CO2 in mL

                                                       Type of      The amount of CO2 in mL   Average
The CO2, that arises, will come into the bottles        sugar
via the tube. The water level will go down
because the density of CO2 is smaller than that        Sucrose      111       94     100,5     102

of water through the CO2 will be above the            D-fructose    101      133      103      112
water. Draw after 48 hours a line on the
bottles at the separation of water and CO2.           D-glucose     95       129      46,5     112

Disassemble the formation of the experiment.
Fill the bottles with distilled water until it
reaches the marked line. Pour this distilled
water in a clean and dry measuring cylinder.
Measure the quantity of the water exact in
mL. This is the quantity of CO2 that is caused
by the fermentation of the chosen sugars.
Execute this experiment three times in the
same way with the same cleaned and dry
materials and measure instruments.

   140                                                        Discussion
                                                              There was a very small production of bio-
                                                              ethanol because the production is much
                                              measurement 1
    80                                                        bigger when there is an anaerobic situation1.
                                              measurement 2
    60                                        measurement 3
                                                              It was impossible to create an anaerobic
                                              average         situation because of the set-up was inaccurate
                                                              and we could not make it better because of
    20                                                        the materials and lack of space at our school.
          sucrose     fructose   glucose
                                                              Our last D-glucose measurement failed
                                                              because the tube was stopped up.

                                                              It was difficult to put the tube into the cap in
Figure 5: histogram with our measurement                      once, so it took a while. You had to walk to the
                                                              bowl. We did held our finger at the end of the
                                                              tube, but it is very likely that there escaped
We didn’t use the third measurement of D-                     some gas.
glucose by the calculation of the average. In
the discussion is explained why.                              There are also inaccuracies by putting lines on
                                                              the bottles because the bottles were hanging
Table 2: Amount of bio-ethanol
                                                              a bit skew during the measurements.
                                                              There is also an inaccuracy by reading out the
           Sugar                 Average amount of bio-       measure cylinder.
                                      ethanol (mL)

          Sucrose                          0,24               After the experiment there was some solution
                                                              in the small tubes due to the changing
         D-fructose                        0,26
                                                              pressure in the test tube.
         D-glucose                         0,26
                                                              Finally we did not take the mass of the O- and
                                                              H-atoms into account. There is a possibility
                                                              that each solution did not contain as much C-
CO2 in L x 24,5 mol CO2                                      atoms because of the different molecule
Mol CO2 = mol ethanol                                         formulas.
Mol ethanol x mol mass ethanol mass
: density ethanol  volume in L
x 1000  volume bio-ethanol in mL


Out of table 2 you can conclude that D-
fructose and D-glucose cause the largest
production of ethanol, but the difference is so
small that a proper conclusion is not possible.


We would recommend to do the same
experiment, but use larger test tubes with
more sugar and more yeast. You should create
a larger bowl with warm water so that you
have more measurements.

You can also investigate if other types of yeast
cause a larger production of bio-ethanol. You
can use fresh or dried baker’s yeast or other
sorts of yeast.


1: http://nl.wikipedia.org/wiki/Gist







Biologie voor jou VWO B2 deel 1, theme 3


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