you can add NH4 to grouth medium after autoclaning then you can filter the medium by 0.22 um filter

Thanks Ibrahim, I tried that but won't this change the pH?

You can buffer the medium with MES. To avoid degradation due to autoclaving you can filter sterilise the medium at 1x for liquid medium and 2x for solid medium. For solid medium prepare water/ager at double concentration. After autoclaving you add the 2x liquid medium (1:1 ratio), best is pre-warmed at 60C, to make the plates/boxes.

Thanks Eric, I will try this.

Appreciating your help :)

I was wondering however what's the range of the MES? the lowest and the highest it could work under?

Dear Radwa,

The pH range for MES is 5.5 - 6.7 (pKa =6.15). It can be used at a concentration of 0.1% (1 gram/L), but 0.5 gram/L also works fine.

Thanks Eric, that will help.