Effect of ethanol on nitrate and nitrite reduction and methanogenesis in the ruminal microbiota
Effect of ethanol on nitrate and nitrite reduction and methanogenesis in the ruminal microbiota
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DOI：
10.1111/j.1740-0929.2005.00235.x
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发表时间：
2005-02-01
影响因子：
2
通讯作者：
Hino, Tsuneo
中科院分区：
文献类型：
--
作者：
Yoshii, Takahiro;Asanuma, Narito;Hino, Tsuneo
通过体外试验研究了乙醇对瘤胃微生物硝酸盐和亚硝酸盐还原的影响。添加乙醇的混合瘤胃微生物培养物刺激硝酸盐还原，并在更大程度上，亚硝酸盐还原，从而导致亚硝酸盐积累的减少。然而，已知的硝酸盐还原瘤胃细菌，如反刍月形单胞菌，韦荣氏菌和Wolinella succinogenes，不能直接利用乙醇作为电子供体的硝酸盐还原。山羊瘤胃中未发现能利用乙醇的硝酸盐还原菌。然而，当向上述混合硝酸盐还原菌的培养物中添加利用乙醇的混合氢气（H2）产生菌（白色瘤胃球菌和产黄瘤胃球菌）时，观察到硝酸盐和亚硝酸盐的还原。这些结果表明，硝酸盐还原菌利用乙醇利用菌氧化乙醇产生的H2作为电子供体。可以想象，在混合瘤胃微生物培养物中观察到的乙醇对硝酸盐和亚硝酸盐还原的刺激是电子从乙醇转移到硝酸盐和亚硝酸盐通过H2的结果，即从乙醇代谢细菌到硝酸盐还原细菌的“种间氢转移”。因此，在高硝酸盐饮食中添加乙醇可能对预防硝酸盐中毒有效。此外，甲烷产量减少到不到三分之一，通过添加混合硝酸盐还原菌的混合产甲烷菌与混合乙醇利用细菌在培养基中含有乙醇和硝酸盐孵育的共培养。因此，添加乙醇和硝酸盐可能会减少甲烷的产生，而不会抑制瘤胃的整体发酵。
The effect of ethanol on nitrate and nitrite reduction was examined by conducting in vitro experiments with mixed ruminal microbes. The addition of ethanol to cultures of mixed ruminal microbes stimulated nitrate reduction, and, to a greater extent, nitrite reduction, which resulted in a decrease in nitrite accumulation. However, known nitrate-reducing ruminal bacteria, such as Selenomonas ruminantium, Veillonella parvula and Wolinella succinogenes, were unable to utilize ethanol directly as an electron donor for nitrate reduction. No nitrate-reducing bacterium capable of utilizing ethanol was found in the rumen of goats. However, when mixed ethanol-utilizing, hydrogen gas (H2)-producing bacteria (Ruminococcus albus and Ruminococcus flavefaciens) were added to the culture of the mixed nitrate-reducing bacteria described above, nitrate and nitrite reduction was observed. These results suggest that the nitrate-reducing bacteria utilized the H2 that was produced from ethanol oxidation by the ethanol-utilizing bacteria as an electron donor. It is conceivable that the stimulation of nitrate and nitrite reduction by ethanol, observed in the culture of mixed ruminal microbes, was a result of electron transfer from ethanol to nitrate, and nitrite through H2, that is, 'interspecies hydrogen transfer' from ethanol-metabolizing bacteria to nitrate-reducing bacteria. Thus, the addition of ethanol to high-nitrate diets may be effective for preventing nitrate poisoning. Furthermore, methane production was reduced to less than one-third by the addition of mixed nitrate-reducing bacteria to the co-culture of mixed methanogens with mixed ethanol-utilizing bacteria incubated in a medium containing ethanol and nitrate. Therefore, the addition of ethanol and nitrate may decrease methanogenesis without suppressing overall fermentation in the rumen.