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[Yeast] Raffinose versus sucrose

Daniel Bosch via yeast%40net.bio.net (by daniel.bosch from gu.se)
Mon May 26 16:49:37 EST 2008


Regarding filtering vs autoclaving, I have always been told to filter the solutions, like Andrew indicates.

The degradation of sucrose releases a steady supply of glucose/fructose, this condition is similar to growth in a low sugar concentration. Under these circumstances "glucose repression" is largely absent, including the repression of the GAL regulon. I can speculate that if the breakdown of sucrose were more efficient there would be a stronger glucose repression effect. However, there would be a feedback regulatory loop since SUC2, the gene encoding invertase, is also repressed by high glucose/fructose concentrations. 

Finally, In the issue of why some labs may use sucrose over raffinose, a simple reason that should not be overlooked is that raffinose is far more expensive that sucrose. 

Cheers,
dani

-----Original Message-----
>From Andrew Carter <cartera from cmp.ucsf.edu>
Sent Mon 5/26/2008 7:33 PM
To yeast from oat.bio.indiana.edu
Subject [Yeast] RE: Yeast Digest, Vol 36, Issue 13

This is an interesting discussion....  I was always told that raffinose
tends to break down on autoclaving and that the filtered form was
better.

I was wondering why if sucrose is broken down into glucose and fructose,
why the glucose does not repress the galactose promoter in the same way
that glucose in the media does?  
Best wishes
Andrew

-----Original Message-----
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To: yeast from magpie.bio.indiana.edu
Subject: Yeast Digest, Vol 36, Issue 13

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Today's Topics:

   1. Re: Raffinose versus Sucrose (Ilya Soifer)


----------------------------------------------------------------------

Message: 1
Date: Mon, 26 May 2008 10:53:11 +0300
From: "Ilya Soifer" <ilya.soifer from gmail.com>
Subject: Re: [Yeast] Raffinose versus Sucrose
To: yeast from magpie.bio.indiana.edu
Message-ID:
	<1952757a0805260053h60b91c14x30299960d15dd95c from mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"

Dear all,
I have a similar question - some labs use autoclaved raffinose and some
-
filtered raffinose in the media prior to galactose induction.
Does anyone have an idea why and which way is preferrable?
Thanks a lot,
Ilya

2008/5/24 Daniel Bosch <daniel.bosch from gu.se>:

> Hi Kerry,
>
> Both sucrose and raffinose are broken up outside of the cell by the
same
> enzyme, invertase. Sucrose generates glucose and fructose that can be
> immediately transported into the cell and assimilated. Raffinose leads
to
> fructose and melibiose. The latter is broken up by another enzyme,
> melibiase, which is not present in all lab strains. As a matter or
fact, the
> degradation of raffinose will yield less amount of fermentable sugars
(33%)
> in lab strains than sucrose (100%) and therefore it can be considered
a
> poorer carbon source. Neither sucrose nor raffinose should lead to a
major
> repression of the GAL genes.
> Having said this, I don't know why some labs prefer sucrose over
raffinose
> or mixtures of both. An alternative to sugars is the use of
respiratory
> carbon sources, such as glycerol or ethanol. I particular find that
cells
> grow better in a mixture of the two (3% glycerol and 1% ethanol) than
on any
> of them alone.
>
> Hope this was helpful,
>
> Dani
>
>
> Daniel Bosch
> Postdoc in Nyström's lab
> Dept. Cell and Molecular Biology
> University of Gothenburg
> Sweden
>
>
> ------------------------------
> From Kerry Geiler <kgeiler from gmail.com>
> Sent Sat 5/24/2008 12:50 AM
> To yeast from magpie.bio.indiana.edu
> Cc
> Subject [Yeast] Raffinose versus Sucrose
>
> HI,
> I have a question about whether yeast grow better in sucrose and
raffinose
> or a combination of both.  I am using galactose induction, so I cannot
grow
> my strains in glucose.  I have inquired with many nearby labs and some
use
> 2% sucrose, some use 2% raffinose, and some use 2% sucrose, 1%
raffinose.
>  However, none of these labs can tell me why they made this decision
(it
> seems to be a part of their lab culture).  Does anyone know the
differences
> between yeast growth in sucrose vs raffinose?  Do either of these
sugars
> inhibit metabolism of the other sugar?  Any information that will
inform my
> decision of which sugar to choose would be greatly appreciated.
Thanks!
>
> Kerry Geiler
> kgeiler from gmail.com
> ------------------------------
>
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