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

Lutz E. Lutz.essers at web.de
Thu Jun 24 09:57:09 EST 2004


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? 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,

Lutz Essers  / Lutz.Essers at web.de



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