The rate of fermentation at different temperatures
Abstract
For this experiment, 3 fermentation tubes (contain yeast) for each different temperature tested were used to determine the effect of temperature on the rate of glycolysis. Fermentation is an anaerobic reaction that happens in the absence of oxygen, while cellular respiration happens with the help of oxygen. Both of them involve in breaking down sugar to release energy. But fermentation produces a small amount of energy and a large amount of carbon dioxide. The fermentation is presented in this experiment by placing the tubes in their water bath for every ten minutes for 30 minutes and then measuring the amount of CO2 that has been get rid of it during the fermentation every ten minutes in four different temperature of water baths. That is the way of knowing how the rate of glycolysis differs by the effect of the temperature. Before doing the experiment, it was hypothesized that the rate of fermentation in the warm bath is higher than the hot, cold and control. The null hypothesis was that there would be no change of the rate of fermentation that has been hypothesized. Before that it was hypothesized: 1- The rate of fermentation in the warm bath is higher than the control bat. 2- The rate of fermentation in the control bath is higher than the cold bath. 3- The rate of fermentation in the control bath is lower than the hot bath. The result has shown that the rate of fermentation in the warm bath is higher than the rest of the other baths. The result was accepted because the t-values of the hot, cold and warm versus control were different. So, the hypotheses are accepted and the null hypothesis is rejected. The conclusion could be that the temperature has obvious effects on the rate of fermentation.
Introduction
Glycolysis is the process in which the glucose is broken down into 2 pyruvate acids. It is a part of the cellular respiration that occurs in the cytosol, and doesn’t require oxygen. Cellular respiration has other two parts beside glycolysis. These two parts are Krebs cycle and Electron Transport System. The main purpose of the cellular respiration is to produce enough amount of energy for the cell’s use. The products of glycolysis are carbon dioxide, water and 2 ATP. On the other side, fermentation is an anaerobic metabolic pathway that breaks down sugars to produce enough amount
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of energy for the cell. Fermentation occurs in the absence of oxygen, and produces a small amount of ATP (2ATP) and a large amount of CO2. The hypotheses that have been created are: 1- The rate of fermentation in warm bath is higher than the control bath. 2- The rate of fermentation in the control is higher than the cold bath. 3- The rate of fermentation in the control bath is lower than the hot bath.
In one of the experiments, the scientists tried to see the result of changing in the plasma membrane composition to check if the plasma membrane can have an adaptive response to low temperature fermentation. They used two stains of Saccharomyces cerivisae and one strain of Saccharomyces bayanus to test the changes in the plasma membrane with the low temperature. They hypothesized that low temperatures restricted yeast growth and lengthened the fermentation. And that’s what they found. As in the experiment of the rate of fermentation at different temperatures, when the fermentation tubes were placed in the cold bath (low temperature), carbon dioxide was not produced because the low temperature restricted the growth of yeast.
Another source mentioned that large wine fermentation requires extreme temperatures, but at the same time, it has to be controlled in order not to lose the production of the fermentation. So, the scientists used automatic systems to balance the rate of temperature to simulate the fermentation of the wine. The experiment of the fermentation on the yeast showed that increasing the temperature would lead the rate of fermentation decreased because the enzymes become denatured and inactive. With the warm bath, the average of carbon dioxide was increasing significantly because the enzymes were active with the warm temperature (35C). That means that it should be a rising in temperature with controlling it to not let it goes higher, and lead to fail the fermentation.
In another experiment, group of scientists put metabolic tracers in temperature from 4 to 20 degrees C. They hypothesized that increasing temperature will increase the amount of energy produced and reduce carbon use efficiency. They gathered metabolic tracers in one place, and rose
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their temperature. They found that the respiration increased 10-fold. Also, it has been found that the relative activity of metabolic processes and energy production changed. These scientists did another experiment, they compared the metabolic responses to temperature increases in soils from high and low elevation. They found that the shift in activity from pentose phosphate pathway to glycolysis with higher temperature was confirmed in soils. On the other hand, the responses of Krebs cycle, biosynthesis and ATP production were site dependent. It has been concluded that, energy production and use for maintenance and growth processes is still incomplete. This is related to the experiment of fermentation at high temperature. At high temperature, the activity of enzymes changed because it became denatured, and the energy production was incomplete.
Methods
The mixture used in this experiment was prepared by mixing 50 g of glucose and 2 packages of Saccharomyces cerivisae into 1L of lukewarm water. To work on this experiment, there were four different temperature baths. For each bath, three fermentation tubes were filled by 40 mL of the mixture, and were ready to be placed in the baths. The 4 baths were the hot bath (59C), the cold bath (0C), the warm bath (35C) and control bath (23C). First, the tubes were placed in their baths for 5 minutes. Then, the tubes were taken out and flipped in order to get rid of any carbon dioxide that has been produced. After that, the tubes were placed in their baths at ten minutes intervals for 30 minutes to measure the amount of carbon dioxide produced in each tube. After the first ten minutes, the amount of carbon dioxide produced was measured by measuring the bubbles that produced in the top of the tubes. The way of measuring the amount of carbon dioxide was to mark where the bubbles ended by using a ruler and then calculate the volume of them. When measuring the carbon dioxide produced at every ten minutes, the first cm is equal to one mL. Every 0.5 cm after that first cm is
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equal to 1 mL. These steps were repeated two more times. At the end, by getting all the measurements, the t-test value and the standard deviation were calculated.
Results
The fermentation that was kept in the warm bath (34c) has the highest average of carbon dioxide production per minute (0.53 mL/min). The fermentation that kept in the cold bath (0c) has the lowest average of carbon dioxide production per minute (0 mL/min) (Table 1). The production of carbon dioxide decreased after the first 10 minutes in the hot bath (Figure 1). The average of carbon dioxide in the hot bath was 0.031 mL/min. The t-test value of the cold bath was 8.96. The t-test value of the warm bath was 4.86. The t-test value of the hot bath was 8.00. The standard deviation of the cold bath is 0. The standard deviation of the warm bath was 0.058. The standard deviation of the hot bath was 0.005. The standard deviation of the control bath was 0.058.
Discussion
The fermentation that was kept in the cold bath had an average rate of carbon dioxide production (1.3, 2.67 and 5 mL/min) after each ten minutes. The average production of carbon dioxide in the hot bath was (0.9, 0 and 0 mL/min). The average production of carbon dioxide in the warm bath was (4, 6 and 5.3 mL/min). The average production of carbon dioxide in the control bath was (1.3, 2.67 and 5 mL/min). These results showed that the rate of fermentation in the warm bath was the highest, and it produced the most significant amount of CO2. The rate of fermentation of the hot bath (59c) was lower than the warm bath because the enzymes became inactive at high temperature. The rate of fermentation in the cold bath (0c) was the lowest because the motion of the molecules decreased, so that CO2 can’t be produced. The control bath (23c) slowed the process of the fermentation. The t-test values of the hot, cold and warm baths (8.00, 8.96 and 4.86) were more than the critical t-test value 2.78. That showed that the hypothesis that considers that the rate of fermentation in the warm bath is
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higher than the control was accepted, and the null hypothesis was rejected. The hypothesis that assumes the rate of fermentation in the control bath is higher than the cold bath was accepted, and the null was rejected. The hypothesis that considers that the rate of fermentation in the control is lower than the hot bath was rejected, and the null was accepted. These results were meaningful in our real lives. For instance, in bakeries, yeast allowed to room-warm temperature until it grows and be ready to be baked. There are many possible reasons for these results. One of which is that when the temperature is low (cold bath 0C), the reaction of glucose to pyruvic acid will slow down because glucose will not be broken down well in low temperature, which will stop the yield of CO2. Moreover, in high temperature (59C), the yield of fermentation is low because the reaction goes very fast which causes some missing yield and denaturing the enzymes. The warm bath had the highest production of CO2 because there was a control of the temperature, so that the rate of fermentation will be simulated. As the wine fermentation, it needs high temperature, but it requires being enough to keep the fermentation, and not making it inactive (Zenteno, M 44). The cold bath (0C) has a low temperature, and this temperature decreases the motion of molecules. In the experiment of noticing the changes of the plasma membrane while decreasing the temperature, it has been found that the low temperature restricted yeast growth and legthened the fermentation (Torija, MJ 131). Furthermore, increasing the temperature creates a greater amount of energy and metabolic activity (Dijkstra, Paul 2029). Some errors happened during estimating the amount of CO2 because the estimation of CO2 bubbles needs to be more accurate. The result that were concluded can be put into consideration in further future researches either on Saccharomyces cerivisae or any other measurement of the glycolysis. Also, the effect of temperature has noticeable in dealing with any future experiment.
Appendix
t-test values Standard Deviation of Overall Average (mL/min) Overall Average CO2/min. (mL/min) Group
0.058 0.3 control
8.96 0 0 cold
4.86 0.058 0.53 warm
8.00 0.005 0.031 hot
Cumulative Amount of CO2 Produced
30 MIN. (mL) 20 MIN. (mL) 10 MIN. (mL) Temperature
8.97 3.97 1.3 Control
0 0 0 Cold
15.3 10 4 Warm
0.9 0.9 0.9 Hot
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