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Effects of hops (Humulus lupulus L.) extract on volatile fatty acid production by rumen bacteria.
MedLine Citation:
PMID:  20456526     Owner:  NLM     Status:  In-Process    
Abstract/OtherAbstract:
AIMS: To determine the effects of hops extract on in vitro volatile fatty acid (VFA) production by bovine rumen micro-organisms.
METHODS AND RESULTS: When mixed rumen microbes were suspended in media containing carbohydrates, the initial rates of VFA production were suppressed by β-acid-rich hops extract. The rates of VFA production increased over extended incubations (24 h), and hops extract caused an increase in the propionate to acetate ratio. Hops extract inhibited the growth and metabolism of Streptococcus bovis, but Selenomonas ruminantium and Megasphaera elsdenii were not affected. Likewise, the propionate production of M. elsdenii/S. bovis co-cultures, but not M. elsdenii/S. ruminantium co-cultures, was decreased in the presence of hops extract.
CONCLUSIONS: These results are consistent with the hypothesis that the hops inhibit Gram-positive lactic acid bacteria (S. bovis), and the rumen microbial community requires a period of adaptation before normal VFA production resumes. Selenomonas bovis and S. ruminantium both produce lactate, which is the substrate for propionate production by M. elsdenii. However, S. ruminantium has an outer membrane, while S. bovis does not.
SIGNIFICANCE AND IMPACT OF STUDY: The enhanced production of the gluconeogenesis precursor, propionic acid, provides further evidence that plant secondary metabolites from hops could be used to improve rumen fermentation.
Authors:
M D Flythe; G E Aiken
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, Non-P.H.S.     Date:  2010-08-19
Journal Detail:
Title:  Journal of applied microbiology     Volume:  109     ISSN:  1365-2672     ISO Abbreviation:  J. Appl. Microbiol.     Publication Date:  2010 Oct 
Date Detail:
Created Date:  2010-11-05     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9706280     Medline TA:  J Appl Microbiol     Country:  England    
Other Details:
Languages:  eng     Pagination:  1169-76     Citation Subset:  IM    
Copyright Information:
Journal compilation © 2010 The Society for Applied Microbiology. No claim to US Government works.
Affiliation:
USDA, Agricultural Research Service, Forage-Animal Production Research Unit, Lexington, KY 40546, USA. michael.flythe@ars.usda.gov
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