How do i adjust pH of a media - (Apr/21/2006 )

Hello,

I am growing Gluconobacter. The media I am using contains:

5g yeast extract

10g D-Mannitol

1.0g (NH4)2HPO4

2.0g MgSO4 X 7H20

I need to get this to a pH of 5.5. Any suggestions? I was thinking of a potassium phosphate buffer, but the desired buffering range isn't really around 5.5... Thanks

Cheers
dez

-dez-

Just to adjust the pH, I don't think you want to add a buffering system...this is your recipe for gluconobacter-specific media, right?

what is the pH when made as directed? I would think sparing quantities of either ammonium hydroxide, or phosphoric acid (or sulfuric acid) would do the trick, without adding a bunch of unnecessary ions

-aimikins-

yeah, this is the exact media the paper uses, ph 5.5. tested without modification puts it at about pH 7.3. I've been using phosphoric acid to knock the pH down (about 13 drops per liter), but a precipitate was forming so i was looking for something else... maybe HCl?

-dez-

I use HCl to drop down pH of culture media and sodium bicarbonate to alcalinize it.

-frinz-

QUOTE (frinz @ Apr 28 2006, 10:22 AM)

I use HCl to drop down pH of culture media and sodium bicarbonate to alcalinize it.

I would suggest 1M HCl for acidification and 1M NaOH for alkilation. . .don't forget to use a Pasteur pipette or micropipettor to dispense drops into the already autoclaved solution. You may want to do it in a fume hood and also filter sterilize the HCl and NaOH to ensure sterility.

-claytonm-