When preparing MS media (distilled water, MS + sucrose, agar; adjusted to pH 5.8) I have noticed that, after autoclaving, there is a small amount of precipitate in the flask. It mixes back into solution quickly once stirred. Does anyone know what this precipitate might be and how to prevent it?
If it goes into solution after stirring, why are you bothered by this? Strictly speaking, there is still only distilled water, MS+sucrose and agar in the flask, just as before autoclaving. Perhaps the agar/sugar is not mixed in properly and it's not really a precipitate but just undissolved stuff?
Thanks for the answer! I am concerned because usually I pour my culture jars before I autoclave, so mixing after is not an option. For some procedures I pour after autoclaving, so yes, in those instances it is not really a problem. Either way, I boil the media mixture before I autoclave and the sugar and agar always appear to be fully dissolved.
HI Kasey,
Just in case, you can double check the quality of distilled water and expiry of media and agar used in recipe. Sometime these factors can be responsible. Also the autoclave machine parameters. All the best.
hi Kasey,
I always autoclave the media first before pour them into vessels. Even doing so, sometimes, I also saw some small amount of precipitate in the flask. I just shake them, and pour plates. It seems that the precipitate did not bother tissue-culturing too much.
This is from the instruction sheet of Sigma product (see attached document with yellow highlight)-- MS powder:
"Preparing this product in a concentrated form is not recommended as some salt complexes may precipitate."
But, I don't think that you were preparing concentrated form of medium, right?
Nothing is expired and I am not preparing a concentrated form. Perhaps there is more I can do to protect the media bottles from moisture though. Thank you for the replies!
Well I think your agar or suger may be expired. In addition, you must check autoclave machine too.
Good luck
Mineral salts might have calcium components, this precipitation can be due to that and also sometimes altering the pH helps in getting rid of such ppt. as it results in dilution of calcium salts.
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