Yeast fermentation with different carbohydrates

[Emily1914]

I am investigating the rates at which different carbohydrates ferment with yeast by measuring the amount of carbon dioxide produced in each case, I am using glucose, fructose, galactose, maltose, sucrose, and lactose.

I wanted to know if each carbohydrate would be fermented by a different enzyme within the yeast cell, since although my results for glucose were high, and fructose had a medium result, sucrose had the highest reading, a small but significant amount higher than glucose and I thought that this could be due to the fact that hexose and pentose carbohydrates are fermented by different enzymes or some other factor, or simply an error?

Any help as immediate as possible (since I have a short deadline) would be very useful

Thanks

[MichaelXY]

I would have expected glucose to be the highest, as it is ready to begin glycolysis. Sucrose is a disaccharide which needs to be broken down to glucose and fructose. Yeast does have the enzyme for sucrose.

[mith]

You're not using any pentoses....

Carbon dioxide produced is proportional to # of carbon atoms in the molecule, not on which enzymes cleave it.

[MichaelXY]

You're not using any pentoses....

Carbon dioxide produced is proportional to # of carbon atoms in the molecule, not on which enzymes cleave it.

But the lab measures CO2 production VS. Time.
1 gram of Sucrose in tube 1 would essentially have the same amount of carbon as 1 gram glucose placed into tube 2. I therefore would assume CO2 would be produced faster in tube 2 since tube 1 would require enzyme action which I would think has some sort of reaction time.
For example:
Glucose ____/~~~CO2
Sucrose ______/~~~CO2

[Emily1914]

Thanks for the pentose sugars comment... I got a bit mixed up

the results I got are below :


Sugar Bakers yeast Brewers Yeast

Time (mins) 35 40 45 35 40 45

Glucose 7.7 10.7 11.3 5.7 7.7 9.0
Fructose 3.3 4.3 4.7 6.0 8.0 9.0
Galactose 2.7 3.8 4.3 3.5 3.7 4.1
Maltose 3.0 3.5 3.5 4.0 4.7 7.0
Sucrose 2.7 3.0 5.0 6.7 8.3 12.0
Lactose 1.0 1.0 1.3 1.0 1.3 1.8

The figures represent carbon dioxide produced in cm3. I used two seperate strains of Saccharomyces cerevisiae yeast, commonly bakers and brewers yeast, due to a lack of gas syringes I only measured gas produced after 30 minutes since before 30 minutes negligible amounts of gas were produced.

thanks, I hope thats understandable

[mith]

Do a couple more trials, that'll give you an idea of the variance i.e. whether the difference is statistically significant.

An interesting thing to note within your data is differences within groups(sugar) at the different times. Why does the sucrose C02 levels ramp up while the glucose levels seem steady(with relation to time)?

[Emily1914]

The problem is I have no more time to do more trials as I am I have no more lab time.... All of my results are averages form three tests I did...

thanks

[mith]

Then compare the data within your 3 trials. For example, does the sucrose sample consistently produce more than the others? And does that data vary much?

for example if your sucrose data was 8, 7, 15 and your glucose data was 7, 8, 9 it's hard to see whether the reaction went significantly faster even if the average is more.

Another thing, I noticed you mentioned fermentation so I'm guessing you're not allowing oxygen to be present. The ethanol produced from fermentation slows growth/metabolism of the yeast. You can guess the level of ethanol present by the total amount of C02 produced up to that point. Depending on the size of your container(concentration) this may or may not be significant.

[MichaelXY]

Ok since I have no life outside of schoolwork, I decided to plot your data. I agree with mith, another trial would have been useful. And like mith said, note the ramp point of sucrose in both test trials.

[Emily1914]

Thanks very much for the help I am going to look at the data again and compare it again your help has been really useful

thanks

[Emily1914]

Correct structure for fructose???

this one is different ...

http://www.enq.ufsc.br/labs/probio/disc ... uctose.gif

to this one ...

http://hyperphysics.phy-astr.gsu.edu/hb ... uctose.gif

anybody know which one is right???

thanks

[mith]

the furanose and pyranose forms are interchangeable in solution, so they are the same.