Maltose Fermentation by Saccharomyces Cerevisiae - Lab Report Example

Lab report 15th November Fermentation The aim of this experiment was to study the fermentation of maltose by the Saccharomyces cerevisiae yeast. The results obtained indicated that lower concentrations of maltose led to production of higher concentrations of carbon dioxide with time. Higher concentrations of maltose however, initially caused increased production of carbon dioxide. 1. Introduction Fermentation is the process in which carbohydrates are converted into alcohols under anaerobic conditions with the aid of yeasts and bacteria or a combination of both with the concomitant production of carbon dioxide. Maltose is a disaccharide which is composed of two units of glucose joined with an α(1→4) bond. The enzyme maltase splits the maltose into simple glucose molecules which are further transformed by yeast into carbon dioxide and water. Saccharomyces cerevisiae is common yeast normally used in the baking and brewing industry due to the ability of this organism to ferment carbohydrates such as glucose and maltose to produce alcohol. This organism has been used since the ancient times. S. cerevisiae can be differentiated from other yeasts based on its growth characteristics and the physiological trait of fermenting individual sugars (US environmental protection agency n.p). In this experiment, the dependent variables were the concentrations of maltose while the independent variables were the temperature and yeast concentrations. The aim of this experiment was to determine the effect of maltose on the production of carbon dioxide during fermentation. The hypotheses formulated included: HO: The concentration of maltose does not affect the amount of carbon dioxide (CO2) gas produced during fermentation H1: The concentration of maltose affects the amount of carbon dioxide gas (CO2) produced during fermentation 2. Materials and methods Four different flasks were each labelled in triplicates according to the concentrations of maltose used in the experiment. They were labelled as different concentrations of 10% maltose solution 5ml, 10ml, 15ml and water in triplicates. The corresponding concentrations of the maltose were then added to the flasks and mixed with yeast suspension, mixed and incubated. The respirometer was then prepared to take 3ml of the different solutions and 1ml of air. The syringes containing the solution were attached to a 1ml pipette and a droplet of water allowed into the pipette. This allowed for the carbon dioxide produced in the fermentation process to cause a rise in the water droplet which was measured after an interval of 10 minutes. The means of the data obtained from the readings were compared using students paired samples t-test. 3. Results   5 ml maltose   10ml maltose   15ml maltose   Control Time Tube 1 Tube 2 Tube 3 Ave Tube 1 Tube 2 Tube 3 Ave Tube 1 Tube 2 Tube 3   C 1 C 2 C 3 Ave 0 0 0 0 0.00 0.1 0.1 0.5 0.23 0.12 1 0 0.37 0 0 0 0 1 0.1 0.1 0.1 0.10 0.1 0.13 0.07 0.10 0.15 0.14 0.5 0.26 0 0 0 0 2 0.1 0.1 0.1 0.10 0.12 0.14 0.08 0.11 0.17 0.17 0.9 0.41 0 0 0 0 3 0.16 0.18 0.18 0.17 0.15 0.16 0.1 0.14 0.21 0.22 0.01 0.15 0 0 0 0 4 0.23 0.25 0.25 0.24 0.16 0.17 0.12 0.15 0.25 0.23 0.14 0.21 0 0 0 0 5 0.31 0.3 0.3 0.30 0.23 0.2 0.18 0.20 0.29 0.3 0.017 0.20 0 0 0 0 6 0.4 0.38 0.39 0.39 0.3 0.24 0.28 0.27 0.36 0.38 0.24 0.33 0 0 0 0 7 0.53 0.49 0.49 0.50 0.32 0.29 0.36 0.32 0.46 0.47 0.31 0.41 0 0 0 0 8 0.68 0.61 0.62 0.64 0.43 0.34 0.42 0.40 0.54 0.56 0.39 0.50 0 0 0 0 9 0.8 0.73 0.72 0.75 0.5 0.41 0.51 0.47 0.7 0.72 0.55 0.66 0 0 0 0 10 0.93 0.89 0.88 0.90 0.58 0.48 0.62 0.56 0.93 0.95 0.7 0.86 0 0 0 0 Table 1: Mean values of CO2 producing during fermentation over time Figure 1: Graph showing the concentration of carbon dioxide produced by different concentrations of maltose over time. The results obtained indicated that the concentrations of carbon dioxide produced generally increased depending on the amount of time. Comparison of the means by paired student’s t-test, however, showed that the means were not significantly different. Comparison of 5ml and 10 ml maltose gave a P value of 0.311 while 5ml and 15ml gave a value of 0.525. Comparison of 10ml and 15ml gave a P value of 0.117. This shows that there were no significant differences in the amount of CO2 produced by different concentrations of maltose over time. From the graph however, it can be observed that the 5ml concentration of maltose gave a higher concentration of carbon dioxide production. However at the start of the experiment, the amount of CO2 produced by 15ml of maltose was higher while that produced by 5ml was the lowest. By the third minute the concentration of carbon dioxide produced by all the concentrations of maltose was equal. The controls which contained water only did not lead to the production of carbon dioxide for the entire period of the experiment. 4. Discussion The yeast species used, the Saccharomyces cerevisiae, ferments carbohydrates such as glucose to produce ethanol. When the maltose was put in the flasks and mixed with the yeast, the maltose was digested by the enzyme maltase into individual glucose molecules (Simpson 192). The individual glucose molecules then undergo metabolism via the process of glycolysis to produce ethanol. In the fermentation process the CO2 produced is trapped as tiny bubbles. The beer brewing yeast produce more ethanol than carbon dioxide as opposed to the bakers yeasts which produce more CO2 than ethanol leading to the rise in the dough (Tom n.p). In alcoholic fermentation, alcohol dehydrogenase oxidizes NADH and generates ethanol (Hames and Hooper 284). 5. Conclusion In conclusion, the results of this study showed that maltose fermentation by Saccharomyces cerevisiae yeast leads to the production of CO2 as a by-product but the concentration of the by product is not dependent on the concentration of the substrate, maltose. Work cited Hames B.D. and Hooper, N.M. “Instant Notes in Biochemistry” 2nd Edition. BIOS Scientific Publishers Ltd, Oxford. 2000 Hui Y.H. “Food Biochemistry and Food Processing.” 2nd ed. John Wiley & Sons, Inc. 2012. Print. Saccharomyces cerevisiae Final Risk Assessment. Biotechnology Program under the Toxic Substances Control Act (TSCA). September 27, 2012 Simpson Benjamin K., Leo M.L. Nollet, Fidel Toldr´, Soottawat Benjakul, Gopinadhan Paliyath andTom Volk. Fungi. 3024 Cowley Hall University of Wisconsin-La Crosse. 1995-2010 Accessed 15th November 2012. Read More