Yeast Frementation Discussion

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Measuring the efficiency of various carbohydrate substrates in yeast fermentation.

Cherrishe Brown
October 3, 2007
Dieldrich Bermudez
BSC 2010L Sect# 0560

As expected in the experiment Glucose, Fructose, and Sucrose were all utilized for fermentation. Based on the rate of evolution of CO2 the yeast was most efficiently able to utilize the substrate Glucose, followed by Sucrose and Fructose respectively. Given more time I believe that Sucrose would have surpassed glucose in total rate (ml CO2/hr) as time and energy was taken as the yeasts cells broke Sucrose down into its glucose and Fructose monomers. That being said with all the substrates being of .14M in addition to being the limiting reagent of the reaction Sucrose entered .14M Glucose and .14M Fructose into the glycolytic pathway where as Glucose only entered .14M of glucose into the glycolytic pathway. Thus Sucrose entered more sugar and had more sugar to be used up by the reaction. However this would have taken more time to become apparent in the data because first the yeast cells would have had to break up the a-glycosidic bond found in Sucrose. The differences in the CO2 evolved in the Glucose and Fructose substrates can be attributed to the place they take in the glycosidic pathway. Fructose is farther down the chain of enzymatic manipulations of the glycolytic pathway than glucose in the production of CO2 and alcohol. In the experiment in addition to the control water, two of the carbohydrate substrates did not evolve any CO2. These two sugars were Lactose and Starch. The amount of CO2 evolved is a measure of the yeasts ability to use the provided substrate for fermentation. Thus it can be said that the yeast was unable to utilize both of these substrates for fermentation. Starch was not efficiently utilized because it was too large of a carbohydrate to enter the yeast cells. Because of this Starch had to first be broken down into its monomers glucose and maltose in order to gain...
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