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Dr. Lesley A. Robertson
Kluyver Laboratory for Biotechnology
Delft University of Technology, the Netherlands
L.A.Robertson at stm.tudelft.nl
R carman <rjcarman at bev.net> wrote:
>We are using chemostats to model the human large bowel ecosystem. The
>amout of inorganic sulfate entering the chemostat vessel (2 umol/d) is
>about the low end of the normal range entering the human colon from
>the ileum (1 to 10 mmol/d). About 7 to 10 d after inoculating the
>chemostat with feces, a black precipitate settles out and coats the
>wall of the chemosat vessel. Up to this point, we can monitor sulfate
>reduction by assaying the amount of sulfide in the chemostat effluent.
>After this time the sulfide levels exceed the theoretical maximum
>possible, though it is true that we do not take into account any
>organic sulfate present in medium components. It looks like sulfide is
>forming aggregates and coming out of suspension, hence the black
>precipitate. In addition, the sulfide traps we use to reduce the
>smell of gas exiting the chemostat follow the same pattern. They
>start colorless but eventually become black. As we would like to run
>the chemostat for up to 30 days and during that time monitor sulfate
>reduction, we have a problem!
>>Do any of you see the same thing? Does anybody have any advice that
>may help us work out the problem?
Sounds like FeS2 in the chemostat. What sort of metals/trace element
solution are you using? Are you using a chelator?
Lesley Robertson
>>Bob Carman
>Phone 1 800 TECHLAB
>E mail: rjcarman at vt.edu
