Fermentation Lab Report

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DePaul University *

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191

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Biology

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May 4, 2024

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DePaul University BIO 191 Deanna Gray October 14, 2021 BIO 191 – Section 3L3B Scientific Method and Fermentation Introduction Fermentation is the metabolic process in which organic molecules are converted into acids or alcohol. It occurs in the absence of oxygen and presence of microorganisms. During fermentation yeast cells, for example, generate energy to grow and divide by breaking down carbohydrates into ethanol and carbon dioxide. This process is important because it is essential for digestion. In experiment one, the rate of fermentation was observed as the concentration of glucose in a solution was changed. The hypothesis was that the concentration of glucose will affect the rate of fermentation. Furthermore, it was predicted that as the concentration of glucose increases, the output of carbon dioxide would also increase with the rate of fermentation. In experiment two, sugars other than glucose were used to test if yeast will undergo fermentation. This section also questioned what the best alternative to glucose was, if applicable. The hypothesis tested was that different sugars would have an effect on carbon dioxide production. The sugar assigned was sucralose, and it was predicted that an increase in sucralose would cause a decrease in the rate of fermentation. Methods In experiment one, three control values were tested along with the experimental group. It was necessary to have two negative control groups, one with a 6% glucose concentration and water, and a second with water and yeast. This was performed to make sure that the variables were pure so that the experiment was not compromised due to contamination. The positive control group used a 6% concentration of glucose so that there was a result to compare the experimental group to. In this experiment, a total of 12 mL was pipetted into each plastic tube with the respective control and experimental solutions so that there was a constant variable of liquid. Negative control group one utilized 4 mL of glucose at 6% concentration and 8 mL of water. The second negative control group consisted of 8 mL of water and 4 mL of yeast, and the third positive group consisted of equal parts of glucose at 6% concentration, water, and yeast. Respectively, the experimental solution consisted of equal parts, but the glucose concentration was tested at 2%.

DePaul University BIO 191 The mixture was then poured into a fermentation tube, where fermentation proceeded for thirty minutes before the height of the gas column in the fermentation tube was measured with a ruler. Experiment One Solutions 1: (-) Control 1 2: (-) Control 2 3: (+) Control 4: Experimental Glucose 4 mL, 6% 0 mL 4 mL, 6% 4 mL, 2% Water 8 mL 8 mL 4 mL 4 mL Yeast 0 mL 4 mL 4 mL 4 mL Table 1. In the table above, the solutions for the control groups and experimental group of 2% glucose are given. In experiment two, the process was altered slightly to test and compare sucralose to glucose. Again, a total of 12 mL was pipetted into each plastic tube to maintain a constant variable of liquid. Negative control group one utilized 4 mL of sucralose and 8 mL water. Control groups two and three did not change. The experimental solution consisted of 4 mL sucralose, 4 mL of water, and 4 mL of yeast. The same process as experiment one was repeated, and the mixture was poured into a fermentation tube and observed after thirty minutes. Experiment Two Solutions 1: (-) Control 1 2: (-) Control 2 3: (+) Control 4: Experimental Sugar 4 mL sucralose 0 mL 4 mL, 6% glucose 4 mL sucralose Water 8 mL 8 mL 4 mL 4 mL Yeast 0 mL 4 mL 4 mL 4 mL Table 2. In the table above, the solutions for the control groups and experimental group of sucralose are given. After the height of the gas column in the fermentation tubes were measured in both experiments, the volume of gas was then calculated. The formula V=πr^2L was used, where the variable L was the height of the gas column measured and the radius of the tube was 0.5 cm.

DePaul University BIO 191 Results In experiment one, each lab group produced data that displayed a higher rate of fermentation when using a higher concentration of glucose. As shown in Table 3, The positive control tube that carried a 6% concentration of glucose consistently produced a higher volume of carbon dioxide compared to the experimental tube which had a 2% concentration of glucose. Experiment One CO2 Production Tube 3:(+) Control Tube 4: Experimental Group Volume CO2 (mL) Volume CO2 (mL) 1 2.35 1.18 2 3.14 1.57 3 2.75 1.18 4 2.67 0.628 5 3.3 1.57 AVG 2.842 1.2256 SD 0.380355097 0.386816235 SE 0.170099971 0.172989479 Table 3. In the table above, the volume of CO2 produced after fermentation is shown for the positive control and experimental groups. The corresponding averages, standard deviations, and standard errors are also shown. (+) Control (6%) Experimental (2%) 0 0.5 1 1.5 2 2.5 3 Experiment One - Average Volume of CO2 Produced Volume CO2 Produced (mL) Figure 1. The bar graph above displays the average volume values derived from experiment one.

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