monensin and 2-bromoethanesulfonic-acid

Rumen inoculum was cultured in specially designed fermenters that allowed simultaneous measurement of pH, oxidation-reduction potentials, and gas production. The cultures were maintained at pH 6.8 by addition of 1 M NaHCO3 and continuous infusion of artificial saliva. Gas flow was maintained at 20.0 ml/min with a stream of O2-free N2. Monensin at 7.0 micrograms/ml inhibited CH4 production 49% below control concentrations. The sodium salt of 2-bromoethanesulfonic acid added at an initial concentration of 5 x 10(-5) M inhibited CH4 production by 86% and increased H2 production from less than .5 mumol/min in the control to 24.5 mumol/min in the inhibited fermenter. The redox potentials in the control fermenter remained above -.20 V and did not change with the addition of monensin. Bromoethanesulfonic acid rapidly decreased the redox potential in the fermenter to -.33 V. Volatile fatty acid production was not significantly altered by the addition of 2-bromoethanesulfonic acid. The addition of monensin gave the expected decrease in acetate:propionate ratios, decreased acetate and butyrate production, and increased valerate (but not propionate) production.

Topics: Alkanesulfonates; Alkanesulfonic Acids; Animals; Cattle; Euryarchaeota; Fatty Acids, Volatile; Fermentation; Methane; Monensin; Oxidation-Reduction; Rumen

The effects of monensin, 2-bromoethanesulfonic acid (2-BES) and pyromellitic diimide (diimide) on gas and volatile fatty acid (VFA) production by the rumen microbiota were compared in mixed culture. Oat hay, a hay-concentrate mixture (48% hay, 43% concentrate) and a soluble carbohydrate mixture were used as substrates for microbial growth. The highest concentrations of diimide (10 ppm) and 2-BES (30 microM) decreased methanogenesis by 97 and 76%, respectively, while H2 accumulation was increased 30- and 20-fold, respectively. The effect of monensin on methanogenesis was less dramatic as 10 ppm decreased CH4 accumulation 16% and H2 did not accumulate. Diimide and 2-BES decreased the acetate:propionate ratio with the hay (P less than .05) and soluble carbohydrate mixture (P less than .025). The numbers of saccharolytic, cellulolytic and methanogenic bacteria from sheep fed a diet with diimide (60 ppm) did not differ significantly from sheep fed a control diet. Semicontinuous culture incubations indicated that the mixed rumen microbial population could adapt and degrade diimide after 24 h of incubation.

Topics: Alkanesulfonates; Alkanesulfonic Acids; Animals; Bacteria; Cattle; Fatty Acids, Volatile; Female; Fermentation; Furans; Gastric Juice; Imidoesters; In Vitro Techniques; Methane; Monensin; Rumen