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M63 minimal media problems

M63 minimal media

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#1 gorbster

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Posted 04 January 2014 - 02:29 PM

Hello,

 

I have been trying to make M63 minimal media using a standard recipe that is consistent across a number of protocol manuals and online sources.  Below is the recipe I have been trying:

 

For 1 liter of medium add:

 

2g          (NH4)2SO4

13.6g     KH2PO4

0.5g       FeSO4.7H2O

MilliQ water to 1L

 

Adjust to pH 7 using KOH

Autoclave, cool

Add 1mL 1M MgSO4

 

All seems to go well until I begin to adjust the pH using KOH.  As soon as I begin adding KOH the solution begins to turn a dark dingy gray and begins to flocculate a fluffy grayish-brownish precipitate. 

 

Any ideas on what I might be doing wrong or thoughts about how to correct this problem?

 

Thanks for any help.


Edited by gorbster, 04 January 2014 - 02:36 PM.


#2 bob1

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Posted 04 January 2014 - 10:59 PM

If you are actually adding 0.5 g (not 0.5 mg?) of FeSO4, then you need to change to adding 0.5 mg.  Too much FeSO4 will precipitate, as will the Fe (III) hydroxide.



#3 El Crazy Xabi

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Posted 05 January 2014 - 05:32 PM

Coincide with bob1, too much iron for that pH. And it will be worse once autoclaved.

 

It's 0.5 mg FeSO4/L
http://www.amresco-i...fu/dfu-j910.pdf



#4 gorbster

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Posted 06 January 2014 - 07:34 AM

Hi,

 

Thanks so much for the help.  Foolish oversight on my part.







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