Why has glucose to be autoclaved seperately?

Shaun D. Black shaun at uthct.edu
Mon Oct 27 12:03:45 EST 1997

Hi Ricky and colleagues,

Frederik Boernke <boernke at ipk-gatersleben.de> wrote:

>In any protocol where sterile glucose is needed,  yeast media for 
>instance, it tells me to autoclave the glucose seperately and to add
>it afterwards. What happens to it when I add it before?

We routinely autoclave glucose (D-glucose, dextrose) with no adverse
effects.  Many will note that it carmelizes, but you really have to
overdo it to get it to carmelize.  30 min at 121degC in water causes
no observable carmelization, and effective microbial growth (when
the complete medium is reconstituted).

On the other hand, as you note, glucose needs to be autoclaved separately
from other media.  This is because glucose is a hemiacetal in equilibrium
with the open chain aldehyde sugar.  Aldoses readily bond to amines to
make "Amadori" products, many of which are irreversible.  Thus, it will
bond with Tris, other amine buffers, amino acids, etc.  Not a good idea
to do this to your media.

I hope this helps you a bit.

Best regards,


  = Shaun D. Black, PhD   | Internet e-mail address:   shaun at uthct.edu  =
  = Dept. of Biochemistry | University of Texas Health Center at Tyler  =
  = Tyler, TX  75710      | World Wide Web:       http://www.uthct.edu  =

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