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Brewer's Yeast Growth Lab- Fermentation Question

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Brewer's Yeast Growth Lab- Fermentation Question

Postby Nicolodn » Mon Sep 27, 2010 6:52 am

For the Petite strain of brewer's yeast, glucose and Oxygen were added. Ethanol was produced.
At max growth using a spectrophotometer there was cell yield at absorbance 600nm of 0.012 after 20hrs.


The question is, what is the significance of the cell yield and the time taken to reach the maximum?
Could someone give me an idea of what the significance is.
This was in comparison to a Grande strain+oxygen taking 30 hrs to reach 0.900 and Petite strain+oxygen taking 30hr to reach max of 0.150.
Does it have to do with build up of ethanol=toxic?


Also, what would the limiting factor of the growth have been?
Would it have been the amount of glucose available, or that due to high density of cells- the toxicity would have killed the yeast?

~~~~~~~~~~~~~~~~~~~~~NEW QUESTION~~~~~~~~~~
What is the significance in my results that Yeast + GLucose+O2 has the least amount of extracellular glucose than Yeast+ glucose+ no O2 ?

Thanks.
Last edited by Nicolodn on Wed Sep 29, 2010 4:49 pm, edited 1 time in total.
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Postby JackBean » Mon Sep 27, 2010 8:11 am

What is the difference between these two strains? What will it suggest about their metabolism?
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Re: Brewer's Yeast Growth Lab- Fermentation Question

Postby Nicolodn » Mon Sep 27, 2010 8:28 am

Is it that Pe strain is anaerobic, it produces less ATP per glucose, it finishes max growth earlier than Gr strain?
I'm confused as to why it takes less time. I thought that it would take the same amount of time as aerobic. Does it mean that anaerobic process is faster?

I don't really get it- Pe strain had a higher growth rate? because it took less time. But, it still produced less cell yield?
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Postby JackBean » Mon Sep 27, 2010 8:54 am

They may reach the maximum faster (but it's quite smaller rigth?), so what matters is, the speed. If one gets 0.9 in 30 hrs i.e. 0.03 hr-1 and the second 0.15 in 30 hrs i.e. 0.005 hr-1, so it's like 6-times slower, rigth?
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Re: Brewer's Yeast Growth Lab- Fermentation Question

Postby Nicolodn » Tue Sep 28, 2010 1:48 pm

I was also wondering, if using a spectrophotometer set at 600nm to measure a sample of culture;
If I get a reading of 0.800 and another sample I get 0.001, that means that there were more cells/growth in 0.800?

Also, about the speed, can I think of it in that way? Isn't the growth exponential?
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Re: Brewer's Yeast Growth Lab- Fermentation Question

Postby canalon » Tue Sep 28, 2010 2:47 pm

Nicolodn wrote:I was also wondering, if using a spectrophotometer set at 600nm to measure a sample of culture;
If I get a reading of 0.800 and another sample I get 0.001, that means that there were more cells/growth in 0.800?

Yes. I would not say 800x more, as the 0.001 is probably out of the linear range of reading (i.e. too small to be entirely trustable), but that would be a 1st approximation
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