Yeast Fermentation Report

Alcoholic fermentation of yeast depends both on the concentration of substrate and yeast

Abstract

The glycolytic pathway is thought to have evolved from by chance from independently evolving enzymes. It is now a complex system that is responsible for break-down of glucose and other sugars. The break-down of these sugars enables organisms to harvest stored in them in a form of ATP. The glycolytic pathway produces a net yield of two ATPs. Yeast undergo fermentation and produce ethanol and carbon dioxide. Carbon dioxide can be used to measure the rate of fermentation. In this study the rate of fermentation was measured through the production of carbon dioxide into a test collection tube over a 25 minute period. Fermentation increases steadily

The tube was closed in one end and the test tube was put into a tub with hot water, at about 55 degrees Celsius. The test tube was then filled with water and the base was left empty to mark a baseline. The test tube was then put in a beaker with hot water. In another test tube different concentrations of yeast and corn were mixed. The combinations included 2× yeast; 1× sugar, 1× yeast; 1× sugar and others.

The controls were set up in the same ways except some lacked either sugar of yeast. Others had double the amount of yeast with no sugar and double the amount of sugar with no yeast. This was set up to monitor the differences. After all this setup rubber stoppers were put in the fermentation tubes and the baseline was marked. In five minute intervals the distance in mm from the baseline mark was monitored. This distance represented the amount of carbon dioxide produced by yeast. This was done for 20 minutes.

Results

Table 1: The rate of production of CO2 by yeast

Time (min) Displacement

This is possible because carbon dioxide, along with ethanol, are products of glycolysis and therefore fermentation. The steady increase of carbon dioxide production of the original experiment means that the yeast was able to absorb sucrose and fructose provided by corn syrup and underwent fermentation. There is a direct relationship between the concentration of yeast cells and fermentation. This phenomenon is illustrated by the second experiment where the concentration of yeast is double that of sugar in the first five minutes there is a drop caused by the subtraction yielded by the control of the experiment. Thereafter we see an exponential increase in the production of carbon dioxide. This means there is a great activity in the break-down of the two sugar substrates by yeast. The control of this experiment lacked sugar but had two times the yeast; the yeast alone produced carbon dioxide that occupied the 5 mm subtracted from the experiment. The minute amounts of carbon dioxide that are produced result from fermentation undergone by yeast cells using the sugars that are already in their system (Barnett and Lichtenthaler,