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

Daniel Bosch via yeast%40net.bio.net (by d_bosch from hotmail.com)
Thu Feb 5 13:01:22 EST 2009


Hi there,

Baker's yeasts loves glucose and fructose, these are consumed earlier than 
any other carbon source present in the medium. Uptake and degradation of 
galactose (and other respiratory carbon sources) is not functional for as 
long as glucose is available. Therefore, to get the GAL promoter to work 
glucose mustn't be present. That's why yeast are grown on raffinose, but in 
principle you could used cheaper carbon sources (e.g. maltose, ethanol, 
acetate). Glucose fermentation yields more energy per unit of time than 
galactose or raffinose, hence glucose allows the fastest growth rate. In 
addition, during glucose growth a large portion of the genome is repressesed 
saving energy, therefore glucose yields a higher OD than other carbon 
sources.

Hope this helps you,

Daniel Bosch
--------------------------------------------------
From: "Andrew Carter" <cartera from cmp.ucsf.edu>
Sent: Wednesday, February 04, 2009 6:27 PM
To: <yeast from oat.bio.indiana.edu>; <yeast from magpie.bio.indiana.edu>
Subject: [Yeast] RE: Yeast Digest, Vol 45, Issue 1

> 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
> Andrew
>
>
>
>
>
>
> -----Original Message-----
> From: yeast-bounces from oat.bio.indiana.edu
> [mailto:yeast-bounces from oat.bio.indiana.edu] On Behalf Of
> yeast-request from oat.bio.indiana.edu
> Sent: Wednesday, February 04, 2009 9:06 AM
> To: yeast from magpie.bio.indiana.edu
> Subject: Yeast Digest, Vol 45, Issue 1
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>   1. raffinose metabolism (Thomas, Arun)
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> ----------------------------------------------------------------------
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> 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>
> Message-ID:
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> <F69C1DF9630D414E9411B4CB41240ABD0B12E6 from XCH.biologie.Uni-Osnabrueck.DE>
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> 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,
> Thomas
>
>
>
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