Biology 2014). From this book, anaerobic fermentation

Biology Internal Assessment

 

 

 

 

 

 

 

 

The Effects on Disaccharides on yeast fermentation
rate

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Yoonseo Choi (Yr13)

 

Introduction

 

During the biology class, we have studied about yeast
fermentation. We only tested in sugar concentration; not in different types of
solution. This is the main reason and the purpose of this experiment, so I was
curious to see the effect of disaccharides on yeast fermentation rate, because
disaccharide is combined with two of monosaccharides’ components. Therefore, there
were two pre – experiments to see the effect of monosaccharide and
polysaccharide on yeast fermentation rate and the amount of solution that has
the best yeast fermentation rate before the main experiment performed.
According to monosaccharide and polysaccharide experiment that was performed
with fructose, glucose, starch and distilled water, it shows starch have
slowest rate of yeast fermentation, because starch is commonly eaten together
by a variety of monosaccharides. Different rate of yeast fermentation might be
dependent upon different percentage amount of solution.

 

Background Information

 

Yeast fermentation has effects from anaerobic
respiration. The pyruvate molecules by glycolysis converted in to carbon
dioxide and ethanol, which is a type of alcohol. This respiration only gives a
small yield of ATP, because there is not further ATP that is produced by
anaerobic respiration of pyruvate. (Walpole, Merson-Davies &
Dann, 2014). From this book, anaerobic fermentation has two types of fermentation;
alcoholic fermentation and lactic acid fermentation. I was wondering the
reaction if I brings the two these fermentations together. When I did lactic
acid fermentation, however it did not take such drastic changes, so I was
curious to see how it responds when it comes to mixing these two types of
fermentations together.

 

Designs

 

Research
Question

 

Previous experimentation with yeast cells revealed that
the rate of fermentation is affected by substrate concentration and enzyme
concentration. This experiment however is investigating the effect of different
types of disaccharides on yeast fermentation while maintaining constant enzyme
and substrate concentrations. How do different types of disaccharides affect the
yeast fermentation rate?

 

Hypothesis

 

That yeast fermentation rate will depend on the enzymes
that yeast possesses to hydrolyze the disaccharides. If maltose is used in the
experiment, then the produced amount of carbon dioxide has the greatest amount,
because maltose is combination of two glucoses. It leads to catalyze the rate.
However, if lactose used in the experiment, then the produced amount of carbon
dioxide has lowest amount, because lactose is condensation with galactose and
glucose.

 

Independent
variables

§   Different types of disaccharides (Sucrose, maltose and lactose)

 

Dependent
variables

§   Rate of yeast fermentation (Amount of carbon dioxide
produced/ ml)

 

Controlled
variables

 

 

Why was it controlled?

Method for control

Time (10 minutes)

To ensure a fair test time it has
to be controlled because if some fermentation tubes are given more time than
others, more yeast fermentation will occur.

All of 4 fermentation tubes have
to set up and start at the same time using stopwatch.

Temperature (26 degree)

Temperature affects to the rate of
yeast fermentation.

Air conditioning of the lab was
kept on at the same temperature throughout.

Concentration of disaccharides’
solutions (5%)

Different concentration of
disaccharides’ solutions could affect to the rate of yeast fermentation. It
could produce more amount of carbon dioxide after 10 minutes.

Disaccharides’ solutions are made by
5% concentration; 1g for disaccharides solutes and 19ml of water.

Concentration of yeast solution

Different concentration of yeast
solution could affect to the rate of yeast fermentation.

Yeast solution is made by 7g of yeast
and 60 ml of water.

Use same yeast

Different types of yeast could affect
to the rate of yeast fermentation. It could produce more amount of carbon
dioxide.

Use a pack of active bacterial culture
(L.bulgaricus, S.thermophilus, L.acidophilus)
 

 

Materials
and Apparatus

§   Yeast

§   Distilled water

§   5% Lactose

§   5% Sucrose

§   5% Maltose

§   4 fermentation tubes

§   Timer

§   3 of 100ml graduate cylinders

§   4 of 200ml beakers

§   4 of Gauze towel

 

Risk
Assessment

All materials are safe to use. Lab coats or safety
goggles do not necessary. However, fermentation tubes are made of glass so they
should be used with caution.

 

 

Procedure

Experiment
with different types of disaccharides; maltose, sucrose, lactose and distilled
water to collect the amount of gas (carbon dioxide) produced.

 

1.       Prepare the disaccharides’ solutions

a)       Put 1g of disaccharides’ solutes (sucrose, maltose and
lactose) and then put 20 degree of 19ml of water. The solution has 5% of
concentration.

b)      Repeat this process with maltose, sucrose and lactose.

 

2.       Set up 4 beakers

a) 20 degree of Distilled water 20ml

b) 5% of maltose solution (20ml) within 20 degree.

c) 5% of lactose solution (20ml) within 20 degree

d) 5% of sucrose solution (20ml) within 20 degree

 

3.       Make the yeast solution as 7g of yeast and 60ml of water.

4.       Put 15ml of yeast solution from step 3 for each beaker.

5.       Mix the solution of disaccharide and yeast solution together.

6.       Pour the mixed solution in each fermentation tube.

7.       Keep out the gauze towel to catch all of carbon dioxide
that is produced inside the fermentation tube.

8.       Measure the amount of carbon dioxide produce by
fermentation tube after 10 minutes.

9.       Repeat above steps as ten trials.

 

Table 1:
The amount of gas (carbon dioxide) produced with disaccharide – sucrose,
lactose, maltose and distilled water after 10 minutes and the average amount of
carbon dioxide produced with disaccharides with the standard deviation

 

Trials

Distilled water

Sucrose

Lactose

Maltose

1

0

15

0.1

19.4

2

0

14.8

0.1

19.5

3

0

15.2

0.1

19.4

4

0

15.1

0.1

19.4

5

0

14.8

0.1

19.7

6

0

15.2

0

19.3

7

0

15

0.2

19.6

8

0

14.9

0.1

19.4

9

0

15.1

0.2

19.3

10

0

14.8

0.1

19.4

Average

0

14.99

0.11

19.44

Standard deviation

0

0.16

0.06

0.13

 

 

This experiment measured the amount of
gas (carbon dioxide) produced with disaccharides such as maltose, sucrose and
lactose. It is performed after 10 minutes with 10 trials. Maltose has the
greatest amount of carbon dioxide produced based on the average amount of gas
(19.44ml). Sucrose has the second greatest amount of carbon dioxide produced
based on average amount of gas (14.99ml). Lactose has the least amount of
carbon dioxide produced based on average amount of gas (0.11ml) from these
disaccharides. Distilled water does not have any fermentation, so it has 0ml of
carbon dioxide produced. These standard deviations have less than 1 and close
to zero. They show the values of this experiment are consistent. This data
support the hypothesis that maltose has greatest rate of fermentation which
results in high amount of carbon dioxide and lactose has least rate of
fermentation which results in low amount of carbon dioxide.

Data processing:

1.     Calculating
the average of each trial by adding up the value of trials and divide by total
number of trials.

 

Example:
The amount of gas produced with sucrose after 10 minutes

Step
1: Plot all data that is collected:

Step
2: Calculate

Step
3: Repeat this process with data by other two disaccharides; lactose and
maltose.

 

2.     Calculating
the standard deviation by following formula:

 

This
calculations performed by Excel software programmer. This is graphed on average
graph by use of error bars.

Graphing
raw data:

Figure 1:
The amount of gas (carbon dioxide) produced with disaccharide – sucrose,
lactose, maltose and distilled water after 10 minutes

 

 

The graph represents the produced amount of carbon
dioxide after 10 minutes within 10 trials based on distilled water and three
different types of disaccharides. Distilled water does not have any produced
amount of carbon dioxide, so the graph shows ‘0’ values for distilled water.
Lactose has little produced amount of carbon dioxide such as 0.1ml and 0.2ml,
so the graph shows little bit above from the values of distilled water. Sucrose
has more produced amount of carbon dioxide than lactose, but not more than
maltose. Sucrose mostly have 15ml produced amount of carbon dioxide. Maltose
has greatest value of produced carbon dioxide; mostly has 19ml produced amount
of carbon dioxide. All trials for each disaccharide have fairly consistent
produced amount of carbon dioxide. This data supported the hypothesis as well.

 

 

 

Figure 2: The average amount of gas (carbon dioxide)
produced with disaccharide – sucrose, lactose, maltose and distilled water
after 10 minutes

 

 

The
graph represents the average produced amount of carbon dioxide after 10 minutes
based on distilled water and three different types of disaccharides. It clearly
shows that maltose has greatest value (19.44ml) of produced amount of carbon
dioxide, and sucrose has second greatest value (14.99ml) of produced amount of
carbon dioxide. Lactose has least value (0.11ml) of produced amount of carbon
dioxide. This error bars represent the collected data has significant value and
consistent, because they have small standard deviations.

 

 

Conclusion and Evaluation

Conclusion

 

The purpose of the experiment is the effects of different
types of disaccharides to the rate of yeast fermentation. The hypothesis stated
the rate of yeast fermentation will depend on the different types of
disaccharides on the rate of yeast fermentation. If maltose used in the
experiment, then the produced amount of carbon dioxide has greatest amount,
because maltose is combination of two glucoses. It leads to catalyze the rate.
However, if lactose used in the experiment, then the produced amount of carbon
dioxide has slowest amount, because lactose is condensation with galactose and
glucose. The data which is collected by experiment support the hypothesis. The
standard deviation of the results were also 0, 0.16, 0.06 and 0.13, which are
all smaller than 10. It shows the precise and accurate data has collected by
the experiment.

 

According to table 1, it shows the amount of carbon
dioxide produced for distilled water and different types of disaccharides based
on 10 trials and collected data after 10 minutes. Distilled water shows 0ml of
produced carbon dioxide, so the average produced amount of gas is 0ml. Sucrose
shows 15ml, 14.8ml, 15.2ml, 15.1ml, 14.8ml, 15.2ml, 15ml, 14.9ml, 15.1ml, and
14.8ml. The average of produced amount of carbon dioxide by sucrose is 14.99ml.
Lactose shows 0.1ml, 0.1ml, 0.1ml, 0.1ml, 0.1ml, 0ml, 0.2ml, 0.1ml, 0.2ml, and
0.1ml. The average of produced amount of carbon dioxide by lactose is 0.11ml.
The last disaccharides, maltose, shows 19.4ml, 19.5ml, 19.4ml, 19.4ml, 19.7ml,
19.3ml, 19.6ml, 19.4ml, 19.3ml, and 19.4ml. The average produced amount of
carbon dioxide by maltose is 19.44ml. Therefore, maltose has greatest value of
produced amount of carbon dioxide by 10 trials and then sucrose has second
greatest value of produced gas. Lactose has the least value of produced amount
of gas from these three types of disaccharides, because lactose is condensation
of galactose and glucose. Lactose’s hydrated form is isomer of sucrose, and
yeast does not contain lactase. It leads to the result that lactose has the
least rate of yeast fermentation. The data supported the hypothesis as maltose
has the greatest rate of yeast fermentation and lactose has the least rate of
yeast fermentation.

 

Maltose consists of two units of glucose joined with an
alpha bond. It is produced when amylase breaks down starch or when glucose is
caramelized. Maltose can do is break maltose molecules, but it can do that very
rapidly and efficiently. This is the reason that the result is shown that the
rate of yeast fermentation on maltose has greatest value.

 

Sucrose has slower yeast fermentation rate than maltose
does, because sucrose is a combination of glucose and fructose. In the
glycolysis process, glucose is utilized while the fructose converts to glucose
before it enter into the process, so sucrose has half of glucose ready to go
and half of fructose has to change. On the other hand, maltose does not need to
hydrolyze any of components because they are all consisting of glucose
molecules.

 

According to pre-experiment that has explained in introduction
of this report, a solution of 5% of maltose is the best for yeast metabolism,
as yeast contains maltase that fermenters maltose. Yeast lacks the necessary
enzymes to hydrolyze lactose. This is the reason that this experiment is
performed based on 5% of solution.

 

 

Evaluation

Limitations
of Experimental Design

 

There are three limitations from these experiments. First
limitation is ‘valve error’. When the fermentation tube has to be closed, these
experiments were used gauze towel for fewer errors; however there are still
errors on experiments. The purpose of gauze towels are catching all oxygen that
are produced during the experiment inside the fermentation tube.

 

Second limitation is lack of sufficient time for yeast
fermentation and small measurement for yeast fermentation. This experiment has
performed with fermentation tubes that only can measure up to 20ml, so this is
the reason that this experiment has collected after 10 minutes. If the
experiment kept over 10 minutes, then the amount of gas produced might be over
20ml. For the further experiment, fermentation tube which can measure more than
20ml of produced gas. If there is a big measurement for yeast fermentation
tube, then the experiment will take more than 10 minutes.

 

Third limitation is using same types of yeast. This
experiment has used same type of yeast and yeast is a controlled variable. For
the further experiment, experiment will be performed with different types of
yeast, because other types of yeast might have different enzymes. Then, there
might have different data with this experiment. This experiment shows maltose
has the greatest rate of yeast fermentation; however lactose has the least rate
of yeast fermentation. If other types of yeast have enzyme lactase, then
lactose might have the greatest rate of yeast fermentation.

 

Suggestions
for Improvement

 

There are three suggestions for improvement. First
suggestion is calculating the rate of monosaccharides like galactose and
fructose, so the results can be compared and discussed with the ones of sucrose
and lactose. For my further experiment, it might be based on mixed solution
from disaccharides and monosaccharides to build up polysaccharides, and then
get the effects for comparing the results from this performed experiment about
disaccharides.

 

The second suggestion is working with yeast that has been
genetically treated to contain lactase and calculate the rate of fermentation
of lactose. This experiment has performed with same type of yeast that is not consisting
of enzyme lactase which could promote the yeast fermentation rate by lactose.
In other words, this further experiment might give a result different from this
performed experiment. There might be two different fermentation that have
explained in background information which are alcohol fermentation and lactic
acid fermentation.

 

The last suggestion is performing yeast fermentation rate
based on different temperature. Yeast has effects from temperature; however
this experiment has performed only based on different types of disaccharides.
In the result, yeast could affect to promote yeast fermentation rate.
Therefore, for my further experiment, I could use same type of yeast depends on
different types of temperature, because the produced amount of carbon dioxide
affect by temperature.

 

Also
for my further experiment, I could use same type of yeast depends on different
types of flour, because yeast is used for baking in real life situation. I
usually bake using yeast and different types of flour, so I want to see the
exact difference of yeast fermentation rate among different types of flour; strong
flour, plain flour and soft flour. In real life situation, bakers who use yeast
in their bread making have to have serious awareness of yeast fermentation. This
would be my purpose for further experiment.

 

Bibliography

Walpole,
B., Merson-Davies, A., & Dann, L. (2014). Biology for the IB
diploma (2nd ed., pp. 78-81). Cambridge, United Kingdom: Cambridge
University Press.

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