Submitted to: Bioresource Technology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/20/1997
Publication Date: N/A
Citation: Interpretive Summary: The production of methane by ruminant animals is a result of microbial activity in the rumen. Methane production results in a loss of energy to the host animal and contributes to the problem of global warming. Methods that can reduce methane production are of value to cattle producers and to the general public. In this paper we examined the use of two chemicals (3-nitropropionic acid and nitrate) for their ability to alter rumen metabolism and methane production. Both chemicals were found to reduce methane production up to 68%. The addition of a specialized bacteria (known as NPOH1) which is capable of using the compounds as food also helped to decrease methane production, especially in the case of nitrate. We conclude that these compounds are useful for the reduction of methane production in ruminants.
Technical Abstract: The production of methane by ruminal bacteria involves the conversion of potentially useful energy rich substrates into a form that cannot be used by the ruminant host. A possible strategy for reduction of ruminal methane production is to divert the flow of reducing substrates away from methanogenesis into alternative electron sinks. In this study we examine the potential for nitrocompounds to serve as such electron sinks. When 3- nitropropionate (5, 10 or 20 mM) was added to mixed populations of ruminal microbes incubated under a H2:CO2 (1:1) atmosphere and with added formate, up to 68% less methane was produced and reductant was directed towards increased propionate production. When nitrate (5, 10 or 20 mM) was added to such populations, methane production was inhibited to a lesser degree than with 3-nitropropionate. Addition of cells of a nitropropionate metabolizing bacterium, strain NPOH1, to mixed ruminal populations did not change the effect of 3-nitropropionate on methane production, although more 3-nitropropionate was metabolized. However, the addition of cells of strain NPOH1, which also reduces nitrate, to such populations drastically changed the effect of nitrate on methane production. In the latter case, reductant was directed away from methane biosynthesis to the reduction of nitrate by strain NPOH1, as evidenced by up to an 18-fold decrease in methane production. These results suggest that 3-nitropropionate and nitrate reduce methane production by different mechanisms.