title: Production of medium-chain volatile fatty acids by mixed ruminal microorganisms is enhanced by ethanol in co-culture with Clostridium kluyveri.
abstract: Mixed bacterial communities from the rumen ferment cellulosic biomass primarily to C2-C4 volatile fatty acids, and perform only limited chain extension to produce C5 (valeric) and C6 (caproic) acids. The aim of this study was to increase production of caproate and valerate in short-term in vitro incubations. Co-culture of mixed ruminal microbes with a rumen-derived strain of the bacterium Clostridium kluyveri converted cellulosic biomass (alfalfa stems or switchgrass herbage) plus ethanol to VFA mixtures that include valeric and caproic acids as the major fermentation products over a 48-72h run time. Concentrations of caproate reached 6.1gL(-1), similar to or greater than those reported in most conventional carboxylate fermentations that employ substantially longer run times.
authors.affiliation: US Dairy Forage Research Center, Agricultural Research Service, United States Department of Agriculture, Madison, WI 53706, USA; Department of Bacteriology, University of Wisconsin-Madison, Madison, WI 53706, USA. Electronic address: Paul.Weimer@ars.usda.gov.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Weimer
authors.affiliation: Department of Bacteriology, University of Wisconsin-Madison, Madison, WI 53706, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Nerdahl
authors.affiliation: Department of Bacteriology, University of Wisconsin-Madison, Madison, WI 53706, USA.
authors.forename: Dane J
authors.initials: DJ
authors.lastname: Brandl
mesh_terms: D000818:Animals; D002208:Caproates; D047010:Clostridium kluyveri / Q000378:metabolism*; D018920:Coculture Techniques; D000431:Ethanol / Q000378:metabolism*; D005232:Fatty Acids, Volatile / Q000096:biosynthesis*; D005285:Fermentation; D000455:Medicago sativa; D012417:Rumen / Q000382:microbiology*; D012418:Ruminants / Q000382:microbiology; D014631:Valerates
chemical_list: D002208:Caproates; D005232:Fatty Acids, Volatile; D014631:Valerates; C037652:hexanoic acid; D000431:Ethanol
keywords: Caproic acid; Carboxylate platform; Clostridium kluyveri; Ethanol; Rumen