Essay: The Impact of Temp. on Yeast Respiration and its Role in Industry



Experimental Report

The Effect of Temperature on Yeast Respiration

Abstract

Respiration is a crucial role in the function of cells and is necessary for the continuation of life. Anaerobic respiration is one of two methods that yeast is able to break down glucose. This report explores the effect that temperature has on the production of CO2 within yeast. Yeast respiration produces Carbon dioxide as a waste product along with Ethanol, this has proved vital within the industry and the production of bread and beer. An experiment was conducted to identify if temperature has an effect on the rate of yeast respiration. If the amount of carbon dioxide produced is related to the temperature then the varying degrees of temperature will ultimately result in the different respiration rates in yeast. In order to carry out the investigation and experiment was performed where yeast and sugar was placed in a test tube each at different temperatures and then the CO2 production was recorded at 5 minute intervals. I predict that the warm temperature will be the optimal for yeast respiration as there will be the most carbon dioxide being released.

Introduction

Yeasts (Saccharomyces sp.) are eukaryotic, single cellular microorganisms that belongs to the Kingdom fungi. It is also known as a facultative anaerobe which means it is able to respire both aerobically and anaerobically and during these processes they produce CO2 and Ethanol as waste products. Yeast has the ability to breakdown sugar into glucose which then causes a release of carbon dioxide. In the scientific industry, the use of microorganisms is vital for the production of basic everyday items. Nature uses microorganisms within the fermentation processes, for thousands of years humans have used bacteria, moulds and yeasts to make a range of food products. Yeast belongs to the traditional biotechnology, within the industry of fermentation Yeast is used within bread, beer and wine making due to its ability to produce CO2 and Ethanol as waste products. (Bioweb, 2002) Yeast contains nutritive substances and proteins in abundant quantities ensuring it uses within the food industry due to its high level of nutritional value. It is also used in non- food industries such as the Biofuel industry due to its ability to produce Ethanol. Yeast can also be used in the medical industry by lowering high cholesterol as well as being utilised in medicine as a source of enzymes. (Elam, 2012)

Yeast is a living organism so an optimal temperature needed to be reached for the activation of energy production to occur. The cellular respiration in yeast can be greatly affected by the temperature. Temperature is able to alter the amount of oxygen needed and the amount of energy used during respiration. If the yeast is in contact with a high temperature then it will die and no cellular respiration will occur. The anaerobic respiration of yeast was explored at different temperatures ranging from 17c to 70c with the amount of CO2  being collected and documented. The aim of the experiment was to determine the way in which temperature affects the ability of cells to conduct a complex metabolic process. This is extremely important within the industry knowing the optimum temperature that yeast produces CO2 will subsequently save time, money and utilities.

Materials and Method

A measuring cylinder was filled to the brim with tap water and place a beaker upside down on top. Then the beaker was inverted and filled ensuring the measuring cylinder remained mostly full. 1g of yeast and 1g of table sugar/sucrose was placed into a test tube, 10ml of distilled water from the beaker was placed in the relevant water bath. The tube was placed into the measuring cylinder and the bung on the test tube. Every 5 minutes for 40 minutes the amount of CO2 produced was recorded. Experiment carried out at 17c, 30c, 40c, 50c and 70c.

Results

Volume of CO2 produced

Time (min) 17c 30c 40c 50c 70c

0 0.00 0.00 0.00 0.38 0.00

5 1.07 1.80 0.78 2.13 6.00

10 1.37 3.40 4.63 5.38 6.67

15 1.57 4.80 9.48 8.94 7.00

20 1.74 5.90 12.88 13.50 7.00

25 2.32 8.20 15.93 16.56 7.00

30 2.60 10.70 19.13 19.19 7.00

35 2.99 12.90 22.13 21.13 7.67

40 3.66 15.50 24.38 22.94 8.00

Fig 1: A table showing the average amount of CO2 produced at different temperatures over 40 minutes.

Discussion

Temperature has a significant effect on the production of CO2, when evaluating the evidence individually it is clear to see that the CO2 production was overall highest at 40c and was lower for 50 and 30. (Figure 1) Enzyme kinetics is able to help us to understand why this happens. CO2 production that occurs at or below the optimal temperature in yeast will be lower as the higher temperatures promotes enzyme kinetics within the cell metabolism (Janssens et al, 2016). Yeast undergoes metabolism in warmer environments, its metabolic rate declines in temperatures above the optimal range (Zakhartsev et al, 2015). During the experiment and observation was made that when the temperature was increased the yeast cells produced more CO2 to an extent. 40c appears to be the optimum temperature as the volume of CO2 production is the greatest at the 40-minute marker the amount of CO2 is 24.38cm3. (Figure 1). The results are consistent with Jenssens et al, (2016) who determined an optimum temperature of 35c. However, this is 5c off of the results we gathered in the grand scheme of things it is relatively close. Also, the water bath temperatures that we used did not include 35, so we can say with confidence that their results support and coincide with the results we gathered. The optimum temperature is not a single temperature but rather a small window where the most CO2 can be produced at its quickest rate. Temperature appears to be the variable that has the greatest influence on yeast metabolism.

The trend that yeast follows with its CO2 production explain logistic growth of a population of unicellular organisms (Jenssens et al, 2016). Yeast has a lag phase, which is the time taken for the cells to adjust to the environment, which in this case would be the temperature, and begin respiring at a notable rate (Dickinson and Schweizer, 2004). This phase was the longest at 17c, as even after 40 minutes the production of CO2 was relatively small only reaching 3.66cm3. However, at 30c there was also a noticeable lag phase as it took 25 minutes for it to commence onto the next phase. Exponential growth follows the lag phase and it is the rapid production of CO2. During the exponential growth phase the cells in the yeast are undergoing anaerobic respiration and therefore producing waste at a rapid rate (Dickinson and Schweizer, 2004). There appears to be significant differences in the rate of CO2 production between each of the different temperatures tested when the yeast was growing exponentially (Figure 1). The yeast showed decreasing rates of CO2 production when the temperature was decreased as well as increased above the optimum temperature.

 Yeast will undertake anaerobic cellular respiration when it is supplied with sugar. As we already know anaerobic respiration uses sugars to produce energy with carbon dioxide as a waste product.

Conclusion