IB BIo Final Yeast Lab

Topics: Yeast, PH, Brewing Pages: 9 (1624 words) Published: December 9, 2014
Kimberly Prete
10.5.14
IB Biology
Yeast Fermentation Lab

Problem Statement
The purpose of this lab is to identify the optimal pH at which enzyme activity is the greatest depending on how many bubbles are produced during the fermentation of Saccharomyces Cerevisiae. The independent variable is the pH; this is because it is modified as the controlled factor. The dependent variable is enzyme activity that is measured in number of carbon dioxide bubbles produces per sixty seconds. It is the dependent variable because its value is relative to the pH solution. The constants are room temperature that is maintained thought-out the whole experiment, the yeast solutions with different pH will all come from the same initial solution, and the same amount of active yeast and sugar will be placed in each solution.

Hypothesis
Different enzymes have different optimal pHs at which they work best. The purpose of this investigation is to see the effect pH has on how much carbon dioxide is produced when Saccharomyces Cerevisiae is fermented. “Fermentation is a process used to produce wine, beer, yogurt and other products. Fermentation is a metabolic process in which an organism converts a carbohydrate, such as starch or a sugar, into an alcohol or an acid. For example, yeast perform fermentation to obtain energy by converting sugar into alcohol” (Masel and Blowers, 2007). Yeast has an optimum range for pH like every other enzyme. S. Cerevisiae will produce the most carbon dioxide between 3 and 5 this is because the optimum range is 2.75 to 4.25 “… pH, ranging from 2.75 to 4.25, is also considered an important factor for the survival and growth of yeasts” (Fleet and Heard, 1993). This indicates that enzyme activity will be highest at the pH of 3 and 5 because it is the greatest amount of metabolic products that are produced. Due to the optimum environment the pH of either 3 or 5 will have the most bubbles produced. After surpassing 5 the activity would decrease therefore decreasing the amount of carbon dioxide produced. The reason why the other pH wouldn’t be as active is because the solution would be too basic or too acidic which is when it starts to denature.

Raw Data:
Table 1: Number of Bubbles Produced from Saccharomyces Cerevisiae in a pH of 3

Time Interval
Trial 1
Trial 2
Trial 3
Trial 4
Trial 5
Trial 6
Trial 7
0-60
0
0
1
0
1
0
1
60-120
0
1
0
2
0
0
0
120-180
0
0
0
1
1
1
1
180-240
1
1
1
1
0
0
0
240-300
0
1
0
2
1
0
1
300-360
1
1
0
1
0
1
0
360-420
1
1
1
2
0
0
0
420-480
0
2
3
2
1
2
1
480-540
1
1
2
2
1
1
1
540-600
1
1
2
2
0
2
0
600-660
1
2
2
1
1
1
1
660-720
1
1
3
3
0
1
0
720-780
1
2
1
2
0
1
0
780-840
0
2
2
2
1
1
1
840-900
1
1
2
1
0
1
0
900-960
1
1
1
2
0
1
0
960-1,020
1
1
2
1
1
1
1
1,020-1,080
1
2
0
2
0
1
0
1,080-1,140
1
1
2
1
1
1
0
1,140-1,200
0
1
2
2
1
0
1
Uncertainty- +/- 1 Bubble, +/- 1 Seconds

Table 2: Number of Bubbles Produced From Saccharomyces Cerevisiae in a pH of 5

Time Interval
Trial 1
Trial 2
Trial 3
Trial 4
Trial 5
Trial 6
Trial 7
0-60
0
1
3
0
0
0
1
60-120
0
2
5
0
0
0
0
120-180
1
2
5
0
0
0
2
180-240
1
3
5
0
0
1
2
240-300
0
3
5
0
0
1
1
300-360
2
4
4
0
1
0
0
360-420
1
3
4
0
0
0
1
420-480
1
2
3
0
0
1
1
480-540
2
3
4
0
0
0
0
540-600
1
2
3
0
0
0
1
600-660
2
2
4
0
0
0
2
660-720
2
2
3
0
0
0
0
720-780
2
3
4
1
0
0
0
780-840
2
2
3
0
0
1
0
840-900
1
3
4
0
0
0
1
900-960
1
1
4
0
0
0
1

Bibliography: 1) Fleet, G.H., Heard, G.M., 1993. Yeasts-growth during fermentation. In: Fleet, G.H. (Ed.), Wine Microbiology and Biotechnology. Harwood Academic Publishers, Chur, Switzerland, pp. 42–43.
2) Masel, & Blowers. (2007, January 1). Fermentation of Sugar in Bread by Yeast. Retrieved September 25, 2014.
3) Ceccato-Antonini, S.R.; Sudbery, P.E. (2004). Filamentous growth in Saccharomyces cerevisiae. Braz. J. Microbiol., 35 (3), 173-181.
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