Aim: for each different concentration three trials will be

Aim:

 The Aim of
this practical is to investigate the effect of increasing the glucose
concentration in solution (10%, 20%, 30%, and 40%) on the rate of Yeast
fermentation. This will be done by placing 20 ml of a 40% yeast solution with
20ml of glucose solutions with different concentrations at a temperature of 40
?C , while keeping other factors controlled. The carbon dioxide released from
the fermentation of Yeast over 5 minutes, will be measured using a CO2 sensor
attached to a data logger. The rate at which CO2 is released will reflect the
rate of fermentation of Saccharomyces cerevisiae.

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Variables:

Independent Variable:

·        
Concentration
of glucose solution (10%, 20%, 30%, and 40%): this variable will be altered,
where for each different concentration three trials will be conducted in order
to investigate the how the increase in the concentration of a glucose solution
will affect the respiration in yeast. The different concentrations will be
prepared by diluting glucose in water. For example to prepare a glucose
solution with a concentration of 10%, 10 grams of glucose measured using a
digital balance will be dissolved in 100 cm3 of distilled water
measured using a 100 cm3 graduated cylinder.

Dependent variable:

·        
Carbon
dioxide released: the will be collected from the solution containing yeast and
glucose using a CO2 sensor attached to a data logger. The CO2
released is a product of yeast fermentation which will increase as the rate of
yeast fermentation increases. This will help us differentiate between the
effects of different glucose concentrations on the rate of yeast fermentation.

Controlled variables:

·        
Temperature
(40o c)

·        
Volume
of yeast (20 ml)

·        
Volume
of glucose (20 ml)

·        
Concentration
of yeast (40%)

·        
Time
interval (every 30 seconds for 5 minutes)

·        
pH
(5)

·        
Type
of sugar (glucose)

·        
Type
of yeast (Saccharomyces cerevisiae)

 

 

Control test:

In order to prove that increasing the
concentration of glucose is a factor affecting the rate of yeast fermentation,
a test will be conducted. In this test the solution containing Saccharomyces
cerevisiae will a have a glucose concentration of 0%. Since the solution
doesn’t contain glucose the fermentation will not take place, proving that
glucose is a factor affecting yeast fermentation.

  

Quantitative data:

Table #1

The
concentration of CO2  released
(ppm) (±1000)   measured every 30 seconds
for 5 minutes during the fermentation of Saccharomyces cerevisiae with a
glucose concentration of 10%. In addition, the mean and standard deviation are
calculated for each trial.

Time/s ±0.1

CO2 concentration/ppm (±1000)

 

Trial #1

Trial #2

Trial #3

Mean (ppm)

Standard Dev

0

8168

8000

8040

8069.3

87.8

30

11524

1100

12656

8426.7

6370.3

60

16320

1700

17420

11813.3

8775.7

90

22184

2222

22512

15639.3

11620.9

120

28664

2700

27820

19728.0

14752.7

150

36596

3477

34056

24709.7

18431.8

180

45072

4000

41312

30128.0

22705.5

210

54452

4800

49636

36296.0

27382.4

240

63696

5200

57072

41989.3

32032.2

270

75432

5980

67048

49486.7

37910.4

300

90768

6600

78256

58541.3

45415.5

 

 

 

 

 

Table #2

The
concentration of CO2  released
(ppm) (±1000)   measured every 30 seconds
for 5 minutes during the fermentation of Saccharomyces cerevisiae with a
glucose concentration of 20%. In addition, the mean and standard deviation are
calculated for each trial.

Time/s ±0.1

CO2 concentration/ppm (±1000)

 

Trial #1

Trial #2

Trial #3

Mean (ppm)

standard Dev

0

5868

7312

8076

7085.3

1121.3

30

8928

8720

9880

9176.0

618.5

60

13256

12948

13768

13324.0

414.2

90

18616

18188

18904

18569.3

360.3

120

24384

23832

24676

24297.3

428.6

150

31136

29688

30808

30544.0

759.2

180

38504

36764

37728

37665.3

871.7

210

46512

44508

46124

45714.7

1062.9

240

57040

53156

55148

55114.7

1942.2

270

66844

62548

66716

65369.3

2444.2

300

77580

73568

76564

75904.0

2085.8

 

Table #3

The
concentration of CO2  released
(ppm) (±1000)   measured every 30 seconds
for 5 minutes during the fermentation of Saccharomyces cerevisiae with a
glucose concentration of 30%. In addition, the mean and standard deviation are
calculated for each trial.

Time/s ±0.1

CO2 concentration/ppm (±1000)

 

Trial #1

Trial #4

Trial #5

Mean (ppm)

standard dev

0

5548

5568

6732

5949.3

677.9

30

8816

7584

8064

8154.7

621.0

60

12532

11024

10708

11421.3

974.8

90

16312

15464

14612

15462.7

850.0

120

21472

21272

19908

20884.0

851.1

150

27228

27824

25812

26954.7

1033.5

180

34408

35564

33008

34326.7

1279.9

210

42832

43928

42244

43001.3

854.7

240

53112

53864

52396

53124.0

734.1

270

63692

65092

64344

64376.0

700.5

300

77652

79544

75512

77569.3

2017.3

 

Table #4

The
concentration of CO2  released
(ppm) (±1000)   measured every 30 seconds
for 5 minutes during the fermentation of Saccharomyces cerevisiae with a
glucose concentration of 40%. In addition, the mean and standard deviation are
calculated for each trial.

Time/s ±0.1

CO2 concentration/ppm (±1000)

Trial #3

Trial #4

Trial #5

Mean (ppm)

standard dev

0

11252

9144

7768

9388.0

1754.8

30

15488

12956

11532

13325.3

2003.7

60

21620

18044

16048

18570.7

2823.1

90

29932

23540

21316

24929.3

4472.9

120

40580

29716

26864

32386.7

7237.5

150

53404

37036

34028

41489.3

10427.4

180

68600

45300

41392

51764.0

14710.8

210

87328

54324

50468

64040.0

20259.9

240

98608

66244

60092

74981.3

20691.2

270

100000

79704

72248

83984.0

14362.5

300

100000

90348

85516

91954.7

7374.5

 

Table #5

The calculation
of the average CO2 released (ppm) (±1000) along with the standard
deviation for all three trials during yeast fermentation with different glucose
concentrations (10%, 20%, 30%, 40%) measured every 30 seconds for a total of 5
minutes.

Time/sec

 
10% mean (ppm)

Standard Deviation 

20% mean (ppm)

 Standard Deviation

30% mean (ppm)

Standard Deviation

40% mean (ppm)

 Standard Deviation

0

8069.3

87.8

7085.3

1121.3

5949.3

677.9

9388.0

1754.8

30

8426.7

6370.3

9176.0

618.5

8154.7

621.0

13325.3

2003.7

60

11813.3

8775.7

13324.0

414.2

11421.3

974.8

18570.7

2823.1

90

15639.3

11620.9

18569.3

360.3

15462.7

850.0

24929.3

4472.9

120

19728.0

14752.7

24297.3

428.6

20884.0

851.1

32386.7

7237.5

150

24709.7

18431.8

30544.0

759.2

26954.7

1033.5

41489.3

10427.4

180

30128.0

22705.5

37665.3

871.7

34326.7

1279.9

51764.0

14710.8

210

36296.0

27382.4

45714.7

1062.9

43001.3

854.7

64040.0

20259.9

240

41989.3

32032.2

55114.7

1942.2

53124.0

734.1

74981.3

20691.2

270

49486.7

37910.4

65369.3

2444.2

64376.0

700.5

83984.0

14362.5

300

58541.3

45415.5

75904.0

2085.8

77569.3

2017.3

91954.7

7374.5

 

Table #6

The rate of
reaction for the fermentation of Saccharomyces cerevisiae with different
glucose concentrations (10%, 20%, 30%, 40%)

Glucose concentration:

Rate of reaction (ppm/s):

10%

168.2

20%

229.4

30%

238.7

40%

275.2

Sample calculation for the rate of reaction:

(Mf-Mi) / t= rate of reaction

For example the calculation of the rate of
reaction for glucose concentration 10% is:

(58541.3 – 8069.3) / 300 = 168.2

Rate of reaction= 168.2 (ppm/s)

 

Graph #1:

Graph #2:

 

Conclusion:

After conducting this investigation, I am now able
to conclude the effect of increasing the concentration of the glucose solution
on the rate of yeast fermentation of Saccharomyces cerevisiae. The results
shown in the graph above show that as the concentration of the glucose
increases, the rate of reaction of yeast fermentation also increases gradually.
For example, yeast fermentation with a glucose concentration of 10% had a rate
of reaction of 168.2 ppm/s. However, for the glucose concentration of 40% the
rate of reaction of yeast fermentation was 275.2 ppm/s. This shows that as
glucose concentration increases the rate of reaction also increases. This means
that there is a direct relationship between the dependent variable (CO2 released)
and the independent variable (concentration of glucose solution), where as the
concentration of glucose increases the concentration of CO2 released
also increases meaning that the rate of reaction of yeast fermentation is
increasing.  However, there were many
outliers found in my results. For example, for the glucose concentration of 10%
the concentration of CO2 released (ppm) for trial #1 after 30
seconds was 11524 ppm, for trial #2 1100 ppm, and for trial #3 12656 ppm. Here
trial #2 is an outlier because it has the greatest difference between all three
trials. In addition, my results were not very accurate because the standard
deviation was very high. For example, the standard deviation for glucose
concentration 10% the standard deviation at 300 seconds was 45415.5. All in all
the results proved my hypothesis “as glucose concentration increases the
rate of yeast fermentation also increases” correct.

The scientific reason for the increase of the rate
of reaction of yeast fermentation as the glucose concentration increases is
because yeast is a fungus which needs energy to grow, the energy required by
yeast is supplied by sugar. Yeast uses sugar in order to release ethanol and
energy during fermentation. Therefore, as more sugar is being supplied there
will be a greater release of energy causing the rate of reaction of yeast
fermentation to increase.