Sulfate reduction in bowel-chemostat

Lesley Robertson l.a.robertson at stm.tudelft.nl
Wed Jun 19 04:04:45 EST 1996

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

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