Necessity of ready electron disposal and interspecies hydrogen transfer for the utilization on ethanol by rumen bacteria |
T. Hino, H. Mukunoki, K. Imanishi, K. Miyazaki |
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Abstract |
Ethanol was utilized by mixed rumen microbes, but addition of pentachlorophenol (25 mg/l), a methanogen inhibitor, suppressed the utilization of ethanol. Carbon monoxide (50% of the gas phase), a hydrogenase inhibitor, more strongly suppressed the utilization of ethanol, propanol, and butanol. These results suggest that the major ethanol utilizers are H2 producers. Ethanol utilization was depressed at low pH (below 6.0). Since methanogens were shown to be relatively resistant to low pH, it appears that ethanol utilizers are particularly sensitive to low pH. Ruminococcus albus and R. flavefaciens in mono-culture of these bacteria with methanogens resulted in the utilization of ethanol, i.e., when H2 was rapidly converted to CH4, R. albus and R. flavefaciens utilized ethanol. These results suggest that ethanol is utilized when the electrons liberated by the oxidation of ethanol are rapidly removed, and ready electron disposal in ethanol-utilizing, H2-producing bacteria is accomplished by the interspecies transfer of H2. |
Keywords:
Rumen Microbes; Ethanol; Interspecies Hydrogen Transfer |
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