Are there any scientists here that use PEG or have worked with it and are able to explain me why a sample with PEG and a fungus becomes very low in pH.
(maybe the fungus has some importance in the proces, but maybe its just the PEG that can make a solution lower in pH at certain circumstances).


At the start the sample had a pH of about 7, after 5 months all of a sudden the sample reaches a pH not even higher then 3.

Also important to tell: I only noticed this drastical decrease in pH with samples stored at +20°C.

It didnt happen with samples stored at 5°C.

from what you have told, it is obvious to me that pH change you have observed is growth related. It doesnt have much to do with the presence PEG.