Freezing Solution Turning Yellow

Hi friends–

My lab is running into a strange problem when trying to create freezing solution for our worms: the solution is yellow after we take it out of the autoclave.

Previous lab members have made this solution and it is not yellow, but all those lab members have since graduated so I have no one to ask.

We obtained our protocol from this source: /chinsanglab/lab-protocols/wormlab-recipe-book

I am doing 500mL, so my recipe is as follows:

  1. 119mL 99% glycerol
  2. 2.93g NaCl
  3. 3.4g KH2PO4
  4. 2.8mL 1M NaOH
  5. Bring solution up to 500mL
  6. Autoclave 30 minutes on fluid setting
  7. Once cool, add 150uL of 1M MgSO4 (I did not perform this step since our solution is yellow)

Is this normal? Should we sterilize using a vacuum filter instead? Is our recipe wrong?

Any help is appreciated! (:

Hi Bethany,

We also observed the same effect in our lab.
It seems some component of the freezing solution (maybe the glycerol) must change properties during autoclaving. We, however, see no deleterious effect in our animals and have been using the solution this way with no problem to our frozen animals.

I’d still would be curious to understand what is happening with the solution!


I use the WormBook recipe and have never seen it turn yellow:
S Buffer [129 ml 0.05 M K2HPO4, 871 ml 0.05 M KH2PO4, 5.85 g NaCl] + 30% glycerin (v/v) (autoclave)

Good luck!