4 replies to this topic

[josse]

Hallo all,

would it be bad to autoclave a broth again?

I have a broth, but I need agar, so I was thinking of putting some agar in the bottle and then autoclaving it again.

Is this ok or?

[ProteinWork]

I was told that it's not wise to do a second autoclaving because the pH of the broth will be affected. But I never tested it myself so I don't know whether it's truth or myth. Just make some fresh media to be safe.

[bob1]

Re-autoclaving burns the sugars found in the yeast extract, which may or may not affect the growth of the bacteria.  It is just about as quick to make up a small amount of fresh medium and add agar anyway.

[Julio-Claudian]

Unless you're critically low on media and don't wish to make new ones, then I think it's fine.

Myself have done that twice (and will make sure it'll never be a routine) and things grow well. They get a lil darker that's all. Grows well for me.

But then, I did that with a broth and I'll spare you the reason why I did that. Not sure about agar though since, like Protein Work puts it, if pH changes, it'll affect the agar after cooling.

[gebirgsziege]

depends on the experiment you will need it for; some media will form precipitates or C-sources can be altered when autoclaving for a second time.

If you are working with a standard medium and just want to keep your microbes growing and your microbes do not need some special nutrients its no problem if the medium is autoclaved for a second time. But if you need the medium for an experiment crucial for your research, make a fresh one to be on the save side.