Changes of pH by E. coli in water/sugar solution

[Andrea Rechenburg]

Lutz.essers at web.de (Lutz E.) schrieb:

>We have problems with the interpretation of a simple experiment. Maybe
>someone can give us a little help.
>
>About 20 ml E.coli K12 culture was filtrated carefully through a
>nitrocellulose filter and resuspended in 10 ml deionized water
>(conductivity about 20 µS). During incubation at RT we have measured
>pH and conductivity over a time of several hours. Both parameter
>remained more or less stable. But if we do the same experiment with
>water which contains 2% sugar (glucose, lactose, mannose, trehalose
>were tested) the pH decreased (slowly to a value of about 4) and
>conductivity increased (slowly to about 60 µS and more). My Question
>is: Why?

Hi Lutz,

check, sugar fermentation.
This will solve your problem.

> Is it just an osmotic effect, are there any fermentation
>reactions, which can explain this observation or do you have other
>explanations?
>
>Thanks for your kind help,

Gruesse Andrea
>
>Lutz Essers  / Lutz.Essers at web.de