[Microbiology] re: ethanol degraders

Matt McMahon matt.mcmahon at chee.queensu.ca
Tue Jun 27 16:22:13 EST 2006


At low concentrations, ethanol can serve as a substrate for sulfate reducing bacteria (SRB, anaerobes).  There are several instances in literature where SRB bioreactors have been fed ethanol as a carbon source.  I think other anaerobes (those involved in midlevel anaerobic degradation of organic waste) can also utilize ethanol as an substrate/electron donor.  Anaerobes however need an electron acceptor to utilize whatever electron acceptor/substrate is present.  In the case of SRB, they require sulfate.  One of the metabolic products is H2S(hydrogen sulfide) which smells like rotten eggs and is highly toxic even a PPM concentrations.
 
 
 
___ 
Matthew McMahon, MScE Candidate
Dept. Chemical Engineering, Queen's University 
Kingston Ontario Canada K7L 3N6 
(613) 533-6000 Ext.  75055 (Lab) 75170 (Graduate Offices)



Radium wrote:

> What odorous chemicals do anaerobic bacteria [excluding the
> acetic-acid-producing bacteria] produce when they feed on ethanol in an
> oxygen-free environment? What do these compounds' odors resemble?


You aren't going to find many bacteria that break down EtOH, let alone
in an oxygen-free environment.  EtOH, in high enough concentrations, is
extremely toxic.  That's why I clean off my lab bench with 70% EtOH.

However, there is an organism called Clostridium kluyveri that breaks
down EtOH anaerobically.  It's the only one I know of that can break
down EtOH, but I'm no expert on metabolism.  The reaction that it
carries out is:

     EtOH + Acetate + CO2  -->  Caproate + Butyrate + H2

Caproate smells like goats.  Butyrate smells like vomit.

Since you have an interest in metabolism, you should look into reading
Brock Biology of Microorganisms.  They're now up to the 11th ed.  The
authors (whom I know personally) do a great job of covering metabolic
diversity.




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