Submitted to: Applied Microbiology and Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/21/2011
Publication Date: 3/26/2012
Citation: Weimer, P.J., Stevenson, D.M. 2012. Isolation, characterization and quantification of Clostridium kluyveri from the bovine rumen. Applied Microbiology and Biotechnology. 94:461-466.
Interpretive Summary: In ruminant animals such as dairy cows, multiple species of rumen microbes play a major role in digesting feed. Since ruminants are extremely efficient at converting feed, their microbes are being studied to see if some of them might also have a future role in the industrial conversion of biomass to biofuel. The microbes responsible for producing caproic acid (an energy source for the cow) in the rumen have not been identified. We isolated, from the rumen of a dairy cow, a strain of a bacterium (Clostridium kluyveri) that can convert mixtures of ethanol and acetic acid in the rumen to butyric and caproic acids. This strain is present in only minor amounts in the rumen (though it is abundant in alfalfa silage), but may be useful for industrial conversion of biomass to caproic acid, which can be chemically converted to fuel compounds. The results of this research can be used by scientists modeling the rumen fermentation and by researchers seeking to convert biomass to fuel compounds.
Technical Abstract: A strain of Clostridium kluyveri was isolated from the bovine rumen in a medium containing ethanol as an electron donor and acetate and succinate (common products of rumen fermentation) as electron acceptors. The isolate displayed a narrow substrate range but wide temperature and pH ranges atypical of ruminal bacteria, and a maximum specific growth rate near the typical liquid dilution rate of the rumen. Quantitative real-time PCR revealed that C. kluyveri is widespread among bovine ruminal samples, but is present at only low levels (0.0002 to 0.0012% of bacterial 16S rRNA gene copy number). However, the species is present in much higher levels in lucerne silage (but not corn silage) that comprises much of the cows’ diet. While C. kluyveri activity may explain several observations regarding ethanol utilization and volatile fatty acid production in the rumen, its population size and growth characteristics suggest that it is unlikely to be a major contributor to overall ruminal metabolism in typical dairy cattle. Nevertheless, this strain may have some utility for industrial fermentations to produce caproic acid.