How does the structure of sugar affect the rate of fermentation?

Background Information:

Living things need to obtain energy in order to sustain their presence by performing their vital activities. For most of the vital activities energy is a must have concept. Cellular respiration is an example fort he process of obtaining energy in the form of ATP (Adenosine Triphosphate)There are two main processes to obtain energy by respiration. They are classified as Aerobic and Anaerobic respiration which are distincted by the use of oxygen.

Anaerobic respiration also stated as fermentation is the process to obtain ATP without the use of Oxygen. The process where yeast converts sugar into ethyl alcohol and carbondioxide is called ethyl alcohol fermentation. This is a result of the absence of oxygen for yeast to convert the organic substance (sugar) into cellular energy. This is considered an anaerobic process.

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Yeast, as a member of the fungi family is neither an animal nor a plant,it is an eukaryotic micro organism. In ethyl alcohol fermentation sugar fungi form of yeast is used. The conversion of sugar into carbon dioxide and alcohol provides energy for the yeast cells. Glucose, sucrose, lactose and fructose are the sugars that are often used to perform experiments and observe the process of fermentation.

Glucose is a type of sugar and a subcategory of the monosaccharides. It’s molecular formula is C6H12O6 . Sucrose is a subcategory of disaccharides as a combination of glucose and fructose. It’s molecular formula is C12H22O11. Lactose is another disaccharide derived from glucose and galactose with molecular formula C12H22O11 which makes it an isomer of sucrose. Fructose is a monosaccharide that is also known as fruit sugar and mostly bonds with glucose to form sucrose. It’s molecular formula is also C6H12O6.

The overall process of ethyl alcohol fermentation is the conversion of sugar into CO2 and alcohol (CH3CH2OH). The reaction is shown for glucose is as shown below ;

The simplicity of the chemical reaction is not preserved in reality and the products are far more complex that it is shown in the reaction. Sugar is also incorporated into other unmentioned products such as yeast biomass,acids and glycerol. This fermentation which was done using glucose as sugar was an example for the fermentation of a monosaccharide. Even though the process does dffer slightly,the amount of the released carbon dioxide and alcohol does change through monosaccharides and disaccharides.

The first step of alcoholic fermentation is the cleavage of glycosidic bonds between glucose and fructose by the enzyme invertase. Then glucose molecules are broken down into two pyruvate molecules by glycolysis. Thus as shown in the reaction above,glycolysis causes the reduction of NAD+ to NADH,ADP is converted into ATP and water molecules via substrate-level phosphorylation.

In the background researches of the previous experiments, it was estimated that different sugars would release different amounts of CO2. Glucose was expected to produce more carbon dioxide than other types of sugar because of it’s 6-Carbon structure. Sucrose was expected to be the runner up producer of carbon dioxide after Glucose because of it’s formation by the combination of glucose and fructose. It has also been considered that the attachment of a 5-Carbon sugar to a 6-Carbon sugar would limit the production of CO2. Fructose was not considered to have a major importance in the experiment but it was estimated that it would evolve some carbon dioxide. The smallest expectation was made on lactose because of it’s complex structure and the absence of enzymes that can break down galactose.

As the results, it was seen that in adequate amount of time both glucose and sucrose reached the maximum amount of CO2 release however sucrose reached it faster. Fructose produced a small amount of CO2 where lactose produced almost none.

Therefore it was stated that the structural differences between different types of sugar effects the CO2 release rate during the fermentation process of yeast.

Aim: To investigate the different fermentation rates of different sugars by measuring the CO2 release.

Research Question: How does the structure of sugar affect the rate of fermentation?

Variables:

(Table 1)

Hypothesis:

If the structural complexity of the sugar increases,the rate of ethyl alcohol fermentation increases.

Material & Method

1. Materials

• 100 ml pure water (x4)
• 5 mg yeast (x4)
• 5 mg Fructose
• 5 mg Lactose
• 5 mg Glucose
• 100 ml beakers (x4, %5)
• 500 ml beaker
• Tube (x4)
• Syrnge (x4)
• Vernier competer inference
• Logger pro
• Vernier CO2 Gas sensor
• 250 mL respiration chamber
• Thermometer
• Heater
• Beral pipettes

2. Method

I. 5 mg of Fructose, Glucose and Lactose was measured separately.

II. Measured sugars were put into separated beakers.

III. 500 ml ofpure water was heated until it reached 38-40ºC and kept constant.

IV. 5 mg of yeast was put into tubes.

V. 25 ml of pure water was put into tubes which were filled with yeast (x4)

VI. Filled tubes were put into the pre-heated 500 ml beaker for 10 minutes.

VII. 2 ml of yeast solution was measured each tube using the syringes.

VIII. All of the solutions were added in to the chamber separately and CO2 sensor was put on the chamber.

IX. Amount of C02 release was calculated for each beaker.

X. All steps were repeated for 5 trials.

3. Design

Data Table (Raw Data):

(Table 2)

(Table 3)

(Table 4)

(Table 5)

Average Table (Processing Data):

Calculation: The calculations for calculating the fermentation rate should be done using the formula (Final CO2 release-Initial CO2 release)(ppm)/Time(min). The calculations for the experiment is as following,

• Fructose: (1023. 8-0)/4= 255,95
• Glucose: (2893-0)/4=723,25
• Lactose: (992-0)/4=248
• Water: (1154-0)/4=288,5

Graphs

(Graph 1) Shows that the Final CO2 release of yeast with Fructose is 1023.

(Graph 2) Shows that the Final CO2 release of yeast with Glucose is 2893.

(Graph 3) Shows that the Final CO2 release of yeast with Lactose is 992.

(Graph 4) Shows that the Final CO2 release of yeast with water is 1154.

Conclusion and Evaluation

Conclusion

As it has been seen in the light of the datas taken during the experiment our hypothesis has been proven to be wrong. Because even though Glucose was a monosaccharide it’s fermentation rate has been measured higher than the Fructose who is a disaccharide. The complex structure of Frutose didn’t cause the fermentation rate to be higher. Thus the hypothesis haven’t been proven to be correct.

The information in the background information has led us to assume that the rate of the more complex sugar would be higher because the number of bonds was higher. But the principle monosaccharide Glucose had the highest fermentation rate n 4 minutes followed by the disaacharide Fructose.

The slowest fermentation rate was measured from the solution which consisted of only yeast and pure water. It was already estimated because Ethyl Alcohol Fermentation is focused on producing energy for yeast. But in the lacking of an energy providing substance such as sugar,enery can not be produced.

Thus,we can conclude our experiment by stating that the structural complexity of sugars affect the rate of ethyl alcohol fermentation however it is not the only factor that affects the rate when different types of sugars are used. The type of bonds is also an effective factor on the rate of ethyl alcohol fermentation.

Limitations:

Improvement

The lack of controlling during the heating of the 500 mL beaker caused a uncertainty of the datas of the experiment. We could have used a more precise heater and quickly used it in the solutions. The largest uncertainties were caused by person-based uncertanities. For example if more time was spent or some tools were used in cleaning the respiration chamber the datas of the experiment could have been more accurate. . One of the other limitations during the experiment was that the use of the syringe was hard because of it’s form.

If the stated limitations were decreased to minimum,the datas could have been more precise and accurate.

References

• BiologyMad A-Level Biology. 02 Mar. 2009
• Cohn, Don. (1999) Science in the Real World, Microbes in Action; How Long Will I Be Blue? Universityof Missouri
• Brazillian archives of biology technology. vol. 51 no. 3 Curitiba May/June 2008