Yeast Fermentation

Effects of Various Carbohydrate Substrates on Yeast Fermentation

This experiment was performed to determine which carbohydrate substrates positively influence yeast fermentation since yeast seems to have greater ability to utilize certain carbohydrates. Rate of evolution of carbon dioxide was measured by the amount of carbon dioxide produced over time. We compared the reaction rates in samples with varying carbohydrate substrates at a constant temperature of 35 degrees C. The most efficient carbohydrates, with respect to time and energy, were the ones best suited for the yeast’s “enzyme-based transport system (Vilet, 1993)”, which allows entry into the yeast cell and entry into the glycolytic pathway. Those carbohydrates best suited for the enzyme-transport system had the highest carbon dioxide levels and the greatest reaction rates.

For millennia, humans have used the alcoholic fermentation capability of yeast to produce breads, crackers and a variety of fermented beverages including beer and wine. Yeast are versatile unicellular fungi. They grow rapidly and have simple nutritional requirements. “When yeast degrade nutrients in the absence of oxygen they use the process of glycolysis to produ

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Using the volume of a cylinder formula and the values: distance between levels in the tube arm and time between measurements, the volume of carbon dioxide was calculated and recorded. The high ratio of yeast-starch to carbon dioxide (see Figure 1) caused the reaction rate to grow rapidly as well (see Figure 2). The yeast’s efficiency to use sucrose and thus the ability to break its bond is greater than any carbohydrate tested. Fifteen ml of each of the prepared carbohydrate solutions was poured into its corresponding tube. Lactose and starch were included but did not have a calculable reaction rate. In this process, known as yeast fermentation, there are 2 ATP molecules produced for each

glucose molecule fermented. Carbon dioxide accumulation is an indicator of the rate of substrate degradation in an organism. Measurements along the arm of each tube were taken every thirty minutes, up to one and a half hours, of the amount in length the solution was displaced by carbon dioxide in the tube. A new colored line was made and findings during each interval were recorded (in centimeters). However, the ratio yeast-starch to carbon dioxide is greater than expected. Our focus was carbon dioxide gas as a waste product of fermentation.

Discussion

The results of the experiment supported the hypothesis that the reaction rate increases with a carbohydrate’s ability to enter the yeast’s cell and glycolytic pathway within the allowed time period of an hour and a half.

Results

Figure one shows the carbon dioxide evolved (read in ml) of each of the six experimental tubes compared to time in hours. Since the reaction rate is the measure of the carbon dioxide evolved over time, the greatest level of conversion was also found in the sucrose tube.

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