I have been a little concerned that the 7H9 media for growing mycobacteria becomes cloudy and crashes out of solution after autoclaving. It is fully dissolved before autoclaving and is clear, but once it has been autoclaved a sandy precipitate accumulates at the bottom of the bottle. Is this a standard problem? Is there anything we can do?
I believe its because of the albumin, albumin is getting coagulated when you autoclave the whole solution. separate out the albumin and autoclave it separately and then add it to the final volume. i hope it helps n let me know if it worked.
Hi, I don't believe that to be the problem because we are just autoclaving the broth base dissolved in miliQ water which as far as I can tell doesn't contain albumin. We plan to add the OADC supplement, glycerol and tween-80 after autoclaving.
Hello,
I have experienced this as well. You indicated that your solution was fully clear before autoclaving, I usually heat it to boiling to be extra careful because if it is not completely dissolved it will present with results like what you are seeing. I also experienced an issue where my solution was being autoclaved for 30 minute liquid cycle instead of 15 minute liquid cycle, this caused a similar situation as well. I believe it ended up having to do with the glycerol content of the media being very sensitive to extended heat exposure. Once I corrected these two problems I had not more precipitate at the bottom of my solution after autoclaving. If the precipitate is of a brown color, which I am assuming based on your 'sandy' description, I would assume something is actually burning or denaturing in the autoclave and double check the things I listed above. I purchase my 7H9 from Hardy Diagnostics and I have on a couple occasions received sub-par supplies from them so, it also may not be anything you are doing.
Best
- Badges
- Science topic
- Similar topics
- Medicine
- Disease
- Infectious Diseases