Role Of Expiration Dates Of Yeast Sample Viability

1154 Words Dec 9th, 2015 5 Pages
Role of Expiration Dates in Yeast Sample Viability
Nasser Almoteb
Kathryn Knackstedt
12/9/2015
Biology 2040, 1003

Abstract
Yeasts consume organic compounds (e.g. sugar) to make ATP in a process called fermentation, creating ethanol and carbon dioxide. Dried yeast samples are in a quiescent state; that is, the yeast are in a state of arrested cell growth. Given the differing expiration dates of our yeast samples, we hypothesized that the yeast nearest to their expiration dates would take the longest to produce carbon dioxide.
We used the gaseous carbon dioxide product of yeast’s fermentation reaction to observe the length of time our yeast samples (with four different expiration dates) took to undergo fermentation, by placing our yeast in Ziploc bags. When the yeast produced carbon dioxide the bags expanded. The results of our experiment proved our hypothesis to be incorrect; the yeast with the nearest expiration dates took the shortest amount of time to produce carbon dioxide. The reason for these results might be that due to the yeasts’ shared state of quiescence, their expiration dates did not determine their viability, or speed with which they underwent fermentation, after exiting quiescence; but rather, the nutrient availability present in the system when the yeast exited quiescence could be the important factor in time in which the yeast underwent fermentation.

Introduction Yeasts are chemoorganotrophs, meaning they source the carbon they…
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