5 replies to this topic

[Meg P. Anula]

Hi guys,

 

From the protocol I read we should autoclave the bacterial growth media first, let it cool down before adding glucose (instead of adding together) to avoid sugar carmelization during autoclaving,

 

But I wonder how should I do it:

 

(1) adding glucose powder directly to cooled down media, but will it be sterile to the media?

 

(2) dissolve the glucose in water, filter to sterile, then add to media, but wouldn't it dilute the growth media?

 

I am in dilemma. 

[phage434]

You usually make up a concentrated glucose solution (50%), filter sterilize, then add the appropriate amount to cooled, autoclaved medium. The dilution is minimal, but if it is of concern, you can account for it in the initial volume of the autoclaved medium. i don't know of anyone who does that.

[pito]

I regulary make it for yeast media. I do account for the addition of the extra glucose. So rather than making 1 liter growth medium, I makde 950ml and add 50ml of 40% glucose later on.

 

THe 40% glucose: I autoclave it. I do not bother to filtersterilise it.

For 50% it should also not be a problem.

 

To filtersterlise it: I wonder this will work very well? Its a pretty "thick" solution? I guess to ones who filtersterlise it, heats it to dissolve it correctly.

.

[Meg P. Anula]

Pito, I was warned not to autoclave glucose (with media).

 

So you mean if autoclaving glucose alone is not a problem?

 

Would the solution turn brown (burned) like how when we heated sugar?

 

Also, do we store the glucose solution in 4 degree or room temperature?

Edited by Meg P. Anula, 06 September 2015 - 04:27 AM.

[pito]

I often make sterile 40% glucose , 1 liter, by just autoclaving it.

After autoclaving I use this glucose to add to the medium.

I just store it at roomtemperature.

 

And no: it does not turn brown.

 

After autoclaving, its best to just shake the bottle a bit, to make sure its mixed well.

 

I Always do it like this and never had problems with it. Many others in the lab do it like this as well.

 

if you do make it: use a big magnet to stirr it when you are preparing it because you really need to add a lot of glucosepowder. I Always put some water (lets say 200ml) in my bottle, with a magnet, and then I add the glucose, 100gram per time.

And I add some more water during the preparation untill I have a total volume of 1 liter (glucose+water).

 

Pito, I was warned not to autoclave glucose (with media).

 

So you mean if autoclaving glucose alone is not a problem?

 

Would the solution turn brown (burned) like how when we heated sugar?

 

Also, do we store the glucose solution in 4 degree or room temperature?

 

[Phil Geis]

A great number of media completely formulated glucose and other sugars are routinely autoclaved, including Czapek Dox with 30% sucrose.  Think I recall glucose may a bit less stable with heat and doubt if there's much data for it's stability in routine media but enough apparently remains to be functional.

 

Can you identify the medium and protocol that demands separate sterilization?