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The Antimethanogenic Nitrocompounds Can be Cleaved into Nitrite by Rumen Microorganisms: A Comparison of Nitroethane, 2-Nitroethanol, and 2-Nitro-1-propanol.
Metabolites ( IF 4.1 ) Pub Date : 2019-12-25 , DOI: 10.3390/metabo10010015
Zhen-Wei Zhang 1 , Yan-Lu Wang 1 , Wei-Kang Wang 1 , Yong-Yang Chen 1 , Xue-Meng Si 1 , Ya-Jing Wang 1 , Wei Wang 1 , Zhi-Jun Cao 1 , Sheng-Li Li 1 , Hong-Jian Yang 1
Affiliation  

A class of aliphatic short chain nitrocompounds have been reported as being capable of CH4 reduction both in vitro and in vivo. However, the laboratory evidence associated with the metabolic fate of nitrocompounds in the rumen has not been well documented. The present study was conducted to compare in vitro degradation and metabolism of nitroethane (NE), 2-nitroethanol (NEOH), and 2-nitro-1-propanol (NPOH) incubated with mixed rumen microorganisms of dairy cows. After 10 mM supplementation of nitrocompounds, a serious of batch cultures were carried out for 120 h under the presence of two substrates differing in the ratio of maize meal to alfalfa hay (HF, 1:4; LF, 4:1). Compared to the control, methane production was reduced by 59% in NPOH and by >97% in both NE and NEOH, and such antimethanogenic effects were more pronounced in the LF than the HF group. Although NE, NEOH, and NPOH addition did not alter total VFA production, the rumen fermentation pattern shifted toward increasing propionate and butyrate and decreasing acetate production. The kinetic disappearance of each nitrocompound was well fitted to the one-compartment model, and the disappearance rate (k, %/h) of NE was 2.6 to 5.2 times greater than those of NEOH and NPOH. Higher intermediates of nitrite occurred in NEOH in comparison with NPOH and NE while ammonia N production was lowest in NEOH. Consequently, a stepwise accumulation of bacterial crude protein (BCP) in response to the nitrocompound addition was observed in both the HF and LF group. In brief, both NE and NEOH in comparison with NPOH presented greater antimethanogenic activity via the shift of rumen fermentation. In addition, the present study provided the first direct evidence that rumen microbes were able to cleave these nitrocompounds into nitrite, and the subsequent metabolism of nitrite into ammonia N may enhance the growth of rumen microbes or promote microbial activities.

中文翻译:

瘤胃微生物可将致产氨性的硝基化合物分解为亚硝酸盐:硝基乙烷,2-硝基乙醇和2-硝基-1-丙醇的比较。

据报道,一类脂族短链硝基化合物能够在体外和体内还原CH4。但是,与瘤胃中硝基化合物的代谢命运有关的实验室证据尚未得到充分记录。进行本研究以比较与奶牛混合瘤胃微生物孵育的硝基乙烷(NE),2-硝基乙醇(NEOH)和2-硝基-1-丙醇(NPOH)的体外降解和代谢。补充10 mM硝基化合物后,在两种底物的存在下,在玉米粉与苜蓿干草的比例(HF,1:4; LF,4:1)不同的情况下,进行了严重的分批培养120 h。与对照组相比,NPOH中的甲烷产量降低了59%,NE和NEOH中的甲烷产量均降低了> 97%,LF中这种致产毒作用比HF组更为明显。尽管添加NE,NEOH和NPOH不会改变总VFA的产生,但瘤胃发酵模式却朝着丙酸和丁酸增加,乙酸盐减少的方向转变。每种硝基化合物的动力学消失均与一室模型完全吻合,NE的消失速率(k,%/ h)比NEOH和NPOH的消失速率高2.6至5.2倍。与NPOH和NE相比,NEOH中亚硝酸盐的中间体含量更高,而NEOH中氨氮的产生最低。因此,在HF和LF组中均观察到响应于硝基化合物添加的细菌粗蛋白(BCP)的逐步积累。简单来说,NE和NEOH与NPOH相比,都通过瘤胃发酵转移表现出更高的产甲烷活性。此外,本研究提供了第一个直接证据,表明瘤胃微生物能够将这些硝基化合物裂解为亚硝酸盐,随后亚硝酸盐代谢为氨氮可能会增强瘤胃微生物的生长或促进微生物活性。
更新日期:2019-12-26
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