Synergistic Effects of Natural Hydrogen Acceptors and a Methanogenesis Inhibitor on In Vitro Rumen Fermentation
Résumé
Inhibiting rumen methanogenesis often causes hydrogen accumulation, potentially negatively affecting the rumen
fermentation process. We hypothesized that the use of hydrogen acceptors when methanogenesis is inhibited would
reduce hydrogen accumulation and improve production of useful fermentation end-products. In this study, phenol,
catechol, resorcinol, hydroquinone, pyrogallol, phloroglucinol, and gallic acid were examined as hydrogen acceptors
by in vitro batch culture. Three experiments were performed: in experiment 1 (Exp.1), 0, 2, 4, and 6 mM of each
phenolic compounds were examined to find their optimum concentration; in experiment 2 (Exp.2), each phenolic
compound at its optimum concentration obtained from Exp.1 was combined with 2-bromoethanesulfonate (BES) at 3
μM as a methanogenesis inhibitor; in experiment 3 (Exp.3), the long-term effects of phloroglucinol (36mM) with or
without BES (3 μM) were examined by sequential incubation. The use of 6 mM phenolic compounds in Exp.1 did not
negatively affect volatile fatty acid (VFA) production, ammonia production, and total gas production. Hence, 6 mM of
each phenolic compound was used in Exp.2. In Exp.2, phloroglucinol, gallic acid, and pyrogallol combined with BES
significantly increased acetate production by 47%, 39%, and 36%, respectively. Whereas methane production was
reduced by 75%, none of the phenolic compounds decreased hydrogen accumulation in the early stages of
fermentation. In Exp.3, after three sequential incubations, phloroglucinol combined with BES decreased hydrogen
accumulation by 72% and further inhibited methanogenesis as compared to BES alone. Interestingly, phloroglucinol
alone significantly decreased methane production by 99% with just a numerical increase in hydrogen accumulation
compared to control. Also, phloroglucinol with or without BES increased total VFA, acetate, and total gas productions
and decreased ammonia production. Our results confirmed the potential of phloroglucinol to capture excess
hydrogen and redirect it towards VFA production. These findings will further be evaluated in vivo.