Responses of methane production and fermentation pathways to the increased dissolved hydrogen concentration generated by eight substrates in in vitro ruminal cultures
Responses of methane production and fermentation pathways to the increased dissolved hydrogen concentration generated by eight substrates in in vitro ruminal cultures
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DOI：
10.1016/j.anifeedsci.2014.04.012
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发表时间：
2014-08-01
影响因子：
3.2
通讯作者：
Tan, Z. L.
中科院分区：
文献类型：
--
作者：
Wang, M.;Sun, X. Z.;Tan, Z. L.
瘤胃中产生的氢（H-2）是产甲烷菌生长的主要能量来源，并且以两种形式存在：溶解的H-2（dH（2））和H-2气体（gH（2））。产甲烷菌仅使用dH（2），我们开发了一个简单的程序来估计液体样品中的dH（2）。然后，我们使用这个简单的装置来测量在体外瘤胃培养物的液相中的dH（2），并研究不同浓度的dH（2）产生的8种精料和粗料的甲烷（CH 4）和挥发性脂肪酸（VFA）的生产的影响。液相中较高的dH（2）浓度不会导致气相中较高的gH（2）浓度，表明亨利定律可能无法描述体外孵育时气相和液相之间的关系。过饱和因子在8种底物中大于1，表明dH（2）和gH（2）不平衡，并且H-2在液相中过饱和。浓缩物产生的H-2比草料多，导致每单位饲料产生更多的CH 4。然而，浓缩物被降解到更大程度，如由更高的VFA浓度所指示的，并且相对于来自浓缩物的VFA，产生更少的H-2。dH（2）浓度与丁酸盐和丙酸盐的摩尔比（R-2 = 0.621）正相关，与乙酸盐和丙酸盐的摩尔比（R-2 = 0.853）、乙酸盐的摩尔比（R-2 = 0.902）和单位VFA的净H-2产量（R-2 = 0.744）负相关。结果表明，较高的dH（2）浓度迫使发酵途径朝向产生较少的H-2和产生较多的丁酸和丙酸的途径，这作为电子下沉而节省了H-2的产生。综上所述，dH（2）浓度不能通过gH（2）浓度预测，dH（2）浓度控制CH 4的生成以及VFA和H-2的生成途径。(C)2014爱思唯尔有限公司版权所有。
Hydrogen (H-2) produced in the rumen is a major energy source for the growth of methanogens, and is present in two forms: dissolved H-2 (dH(2)) and H-2 gas (gH(2)). Methanogens use only dH(2), and we developed a simple procedure to estimate dH(2) in liquid samples. We then used this simple apparatus to measure dH(2) in the liquid phase of in vitro ruminal cultures, and to investigate the effects on methane (CH4) and volatile fatty acids (VFA) production of different dH(2) concentrations generated by eight substrates of concentrates and forages. Higher dH(2) concentrations in the liquid phase did not lead to higher gH(2) concentrations in the gas phase, indicating that Henry's law might not describe the relationship between the gas and liquid phases for in vitro incubations. The supersaturation factor was larger than unity across eight substrates, indicating that dH(2) and gH(2) were not in equilibrium, and H-2 was supersaturated in the liquid phase. The concentrates generated greater amounts of H-2 than the forages, leading to more CH4 per unit of feed. However, the concentrates were degraded to a greater extent, as indicated by the higher VFA concentrations, and less H-2 was produced relative to VFA from the concentrates. The dH(2) concentration was positively correlated with molar proportion of butyrate (R-2 = 0.621) and propionate (R-2 = 0.904), and negatively correlated with ratio of acetate to propionate (R-2 = 0.853), molar proportion of acetate (R-2 = 0.902) and the net H-2 production per VFA (R-2 = 0.744). The results indicated that higher dH(2) concentrations forced the fermentation pathways towards those producing less H-2, and more butyrate and propionate, which as electron sinks that spare H-2 production. In summary, the dH(2) concentration could not be predicted by the gH(2) concentration, and the dH(2) concentration controlled CH4 formation and the pathways of VFA and H-2 production. (C) 2014 Elsevier B.V. All rights reserved.