Get rid of yeast but not the bacteria - how? - (Jan/29/2011 )
Hi,
I have some students who is doing some yeast experiments. Now they would like to test the substrates for bacteria (to see if it is nessasary to autoclave it before the yeast is added - it probably would be a good idea 
)
But what if some bacteria is of no matter because the yeast will outpower it? I would like them to plate the media after some tests with bakers yeast.
Could we get rid of the yeast? Could we add something that only kill/inhibit the yeast? Filtrate it?
I am pretty sure that the result will be plates covered with yeast and maybe one or two bacteria colonies that could have been much more if the yeast wasn't there!!
If anybody have any idea please tell me - my students are just at high school level, so if we e.g. get 10% less outcome it is not a great deal 
The methods are the most important (using plates - using filters - using spectrophotometer - etc.)
KemiskeKetty on Sat Jan 29 20:00:51 2011 said:
Hi,
I have some students who is doing some yeast experiments. Now they would like to test the substrates for bacteria (to see if it is nessasary to autoclave it before the yeast is added - it probably would be a good idea
)But what if some bacteria is of no matter because the yeast will outpower it? I would like them to plate the media after some tests with bakers yeast.
Could we get rid of the yeast? Could we add something that only kill/inhibit the yeast? Filtrate it?
I am pretty sure that the result will be plates covered with yeast and maybe one or two bacteria colonies that could have been much more if the yeast wasn't there!!
If anybody have any idea please tell me - my students are just at high school level, so if we e.g. get 10% less outcome it is not a great deal
The methods are the most important (using plates - using filters - using spectrophotometer - etc.)I do not understand it.
Do you want to grow yeast or bacteria?
As far as I understand it, you want to grow bacteria and not yeast? But you also want to use bakers yeast?
Could you explain the experiment a bit better because, I do not completely understand it.
Is it like this: you want to grow bacteria and you also want to test the influence of yeast on the growth of this bacteria by adding some bakers yeast in the medium? Or?
Sorry
We will grow yeast.
And the students want to see if it is nessesary to autoclave the ingredients for the media - yes or no.
To find out this, they will make some plates with ordinary plate count agar to see if there are bacteria in e.g. the peptone/sugar/whatever they are going to test.
NO PROBLEM SO FAR
Then they would also like to see if the media was contaminated during the fermentation. And I guess that the yeast will dominate the culture (I sure hope that ), but they would like to kill or inhibit the yeast in this particular analysis. Simply because the yeast is meant to be - but the bacteria is not.
Of cause there could be loads of other fungi - but this is just high school, and the idea is fun, if it is posible!
You won't find any yeast in the commercial medium, but it is very easy to contaminate it while making up the medium. Any filter with a pore size of 5 microns should filter out yeast but not bacteria.
You could also look under a microscope for bacterial cells... Or maybe a Gram stain?