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[Yeast] RE: Yeast Digest, Vol 45, Issue 1

Andrew Carter via yeast%40net.bio.net (by cartera from cmp.ucsf.edu)
Wed Feb 4 12:27:26 EST 2009

Hi Thomas
Glucose represses the Gal promoter whereas Raffinose doesn't.  If you try
growing up yeast in YPD (2% glucose) and then add galactose you will get no
(in my experience) induction.  If you grow up in YP raffinose and add
galactose the promoter will get turned on immediately.

It turns out however that you can first grow in glucose and then add
galactose.  You just have to make sure that you have used up all your
glucose.  I have been playing with this quite a lot recently (in a large
fermentor) and it works well.  The key for me was using 2X YP and 1% glucose
and waiting until growth plateaus.  Then add in 2% galactose (0.5% and 1%
also work) and induction turned on just fine.  I was using induction from a
gal promoter inserted in the genome and haven't tried it with a plasmid
based system, but my guess is it should work.  The real advantage is that
Raffinose gets really expensive if you want to scale up...  

Not sure why growth is slower in galactose than glucose but I see it alot
(final OD is usually lower as well).
Best wishes

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Subject: Yeast Digest, Vol 45, Issue 1

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Today's Topics:

   1. raffinose metabolism (Thomas, Arun)


Message: 1
Date: Wed, 4 Feb 2009 11:36:10 +0100
From: "Thomas, Arun" <Arun.Thomas from Biologie.Uni-Osnabrueck.DE>
Subject: [Yeast] raffinose metabolism
To: <yeast from magpie.bio.indiana.edu>
<F69C1DF9630D414E9411B4CB41240ABD0B12E6 from XCH.biologie.Uni-Osnabrueck.DE>
Content-Type: text/plain;	charset="iso-8859-1"

Hi everyone, 

To induce a gene under the GAL promoter from a 2micron plasmid, why is it
preferred to grow the cells in raffinose/glucose initially followed by
induction with galactose?

If cells grow slowly in galactose, why is it so? 

Thank you,


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