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The Fermentation of Yeast

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Savraj Sethi 10L The Fermentation of Yeast Aim: To find out how the rate of the fermentation of yeast differs when different PH buffers are used. Introduction The yeasts are a rather unusual family of fungi. Only a few of the several species can form true hyphae. The majority of them consist of separate, spherical cells, which can only be seen under the microscope. They live in situations where sugar is likely to be available. Yeasts are of economic importance in promoting alcoholic fermentation. Yeast cells contain many enzymes, some of which can break down sugar into carbon dioxide and alcohol. This chemical change provides energy for the yeast cells to use in their vital process. Equation: C6H12O6 2CO2 + 2C2H5OH + 118KJ Sugar Carbon Alcohol Energy Dioxide A diagram of a yeast cell Planning 8g of sugar was dissolved in water in a 250 cm3 beaker and 15g of yeast was mixed with that. This was left for 10 minutes for the yeast to become active. Some of the yeast mixture was then transferred to a test tube along with Ph buffer. ...read more.


Firstly, I decided to only note down the volume of gas produced for every 5 minutes. Secondly I decided to ferment the yeast in a beaker and then transfer the yeast using a pipette into a test tube. 15cm3 of yeast and 15cm3 of Ph buffer were used so that the test tube was just about two-thirds full so that there was sufficient gas being produced. Also, I decided to wait until the first bubble of gas was produced and then I started timing the experiment. Each Ph value was repeated twice so that there were three values in total. Table Of Results Ph 3 Time /mins Volume /cm3 1st Repeat 2nd Repeat Average 5 1.8 1.6 1.6 1.7 10 3.6 2.4 2.4 2.8 15 4.1 2.8 2.8 3.2 20 4.7 4.4 4.4 4.5 Ph 5 Time /mins Volume /cm3 1st Repeat 2nd Repeat Average 5 1 0.7 1 0.9 10 2 1.0 2 1.7 15 3.4 3.6 3.6 3.5 20 5 6.0 5.2 5.4 Ph 7 Time /mins Volume /cm3 1st Repeat 2nd Repeat Average 5 1.2 2 2 1.7 10 6 5 6 5.7 15 8 7 8 7.7 ...read more.


There are a few anomalies on my graph, and these have been circled with red pen. A better graph could have been drawn if more results had been taken (more Ph values), but it was inaccurate to measure exactly how much gas had been produced, whilst waiting for the first bubble to appear. Also, Ph testing paper was used, to test the exact levels of Ph buffer and it was found that Ph 6 was more like Ph 5, and also, other Ph buffers were not precise. To improve the experiment I would use better measuring equipment to measure the amount of gas; make sure that I had the exact amount of yeast and sugar, and also make sure that the Ph buffers were not polluted. Further Work For further experiments, I would consider changing the amount of sugar, to see if that affected the rate of fermentation and would take six different values of sugar. Another way of extending the investigation is to use different temperatures to see if that affects the result. I would use a Bunsen burner, and change the air-hole for four different values and then use ice and finally leave it at room temperature. ...read more.

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