Sulfate and nitrate reduction, and methanogenesis in mammalian digestive tract
| Project/Area Number |
05660314
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Zootechnical science/Grassland science
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| Research Institution | Kyoto Prefectural University |
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Principal Investigator |
USHIDA Kazunari Kyoto Prefectural University, Faculty of Agriculture, Associate professor, 農学部, 助教授 (50183017)
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| Co-Investigator(Kenkyū-buntansha) |
KOJIMA Yoichi Kyoto Prefectural University, Faculty of Agriculture, Professor, 農学部, 教授 (80046490)
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| Project Period (FY) |
1993 – 1994
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| Project Status |
Completed (Fiscal Year 1994)
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| Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1994: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1993: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Keywords | methanogenesis / sulfate reduction / rumen / hind gut / 硝酸還元 / 多糖分解 |
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| Research Abstract |
Effect of specific methanogenic inhibitor (BES,2-bromo ethanesulphonate) on hydrogen accumulation from carbohydrate fermentation was investigated with ovine ruminal and porcine caecal mixed microorganisms. Effect of BES was evident with ruminal microorganisms, 100 to 2000 times more hydrogen was accumulated by BES,while 5 to 10 times more hydrogen was accumulated by the same treatment with porcine caecal microorganisms. It was suggested that most of hydrogen is disposed through methanogenesis in the rumen. The numbers of methanogenic and sulfate reducing bacteria were estimated in ovine rumen and porcine caecum. The predominant hydrogenotrophic bacterium was the methanogen in the rumen, while it was sulfate reducers in the porcine caecum. This situation was particular in the rumen, because sulfate reducers are predominant hydrogenotrophs in the most of anaerobic environment. Free sulfate levels in the digesta were measured by ion chromatography using HPLC.Free sulfate levels in the ovi
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ne rumen was as high as 1mM at 1h after feeding, the highest levels after feeding, the levels were gradually declined to zero 4h after feeding. The maximal level was as high as 5mM in the porcine caecum. The levels were constantly higher than those observed in ruminal fluid. The low sulfate levels appear to be responsible for low activity of sulfate reduction in the rumen. In vitro experiments were conducted using ruminal fluid in order to know what level of sulfate is required to enhance sulfate reduction. 98% of hydrogen was disposed through methanogenesis with free sulfate levels below 10mM.Sulfate reduction was enhanced and methanogenesis was reduced at 10mM of free sulfate. However 90% of hydrogen still disposed through methanogenesis even higher sulfate levels (20mM). In vivo experiment was conducted to know the effect of sulfate on methanogenesis and sulfate reduction in the rumen. Free sulfate levels were 3 to 4 times increased by the sodium sulfate dose in the rumen. The numbers of lactate-utilizing sulfate reducers and sulfate reducing activity of digesta increased according to the augmentation of free sulfate. However, H2-utilizing sulfate reducers did not increase. The numbers of methanogens tended to be decreased after sodium sulfate dose, the difference were not consistent between the experimental periods. Lack of clear response of sulfate reducers to increased sulfate levels may be due to the insufficient sulfate augmentation, but it is still suggested that sulfate reducers could not outcompete methanogens in the rumen. The relation between methanogens and H2-producing organisms in the rumen may be so close that the niche is unlikely to be replaced by sulfate reducers. Further studies are required to clarify the relation between methanogens and H2-producing organisms, such as protozoa, chytridiomycete fungi and cellulolytic bacteria. Less
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