USDA, Agricultural Research Service, Forage-Animal Production Research Unit, Lexington, KY 40546, USA.
J Appl Microbiol. 2010 Oct;109(4):1169-76. doi: 10.1111/j.1365-2672.2010.04739.x. Epub 2010 Aug 19.
To determine the effects of hops extract on in vitro volatile fatty acid (VFA) production by bovine rumen micro-organisms.
When mixed rumen microbes were suspended in media containing carbohydrates, the initial rates of VFA production were suppressed by β-acid-rich hops extract. The rates of VFA production increased over extended incubations (24 h), and hops extract caused an increase in the propionate to acetate ratio. Hops extract inhibited the growth and metabolism of Streptococcus bovis, but Selenomonas ruminantium and Megasphaera elsdenii were not affected. Likewise, the propionate production of M. elsdenii/S. bovis co-cultures, but not M. elsdenii/S. ruminantium co-cultures, was decreased in the presence of hops extract.
These results are consistent with the hypothesis that the hops inhibit Gram-positive lactic acid bacteria (S. bovis), and the rumen microbial community requires a period of adaptation before normal VFA production resumes. Selenomonas bovis and S. ruminantium both produce lactate, which is the substrate for propionate production by M. elsdenii. However, S. ruminantium has an outer membrane, while S. bovis does not.
The enhanced production of the gluconeogenesis precursor, propionic acid, provides further evidence that plant secondary metabolites from hops could be used to improve rumen fermentation.
确定啤酒花提取物对体外瘤胃微生物挥发性脂肪酸（VFA）生产的影响。
当混合瘤胃微生物悬浮在含有碳水化合物的培养基中时，富含β-酸的啤酒花提取物抑制了 VFA 的初始产生速率。随着孵育时间的延长（24 小时），VFA 的产生速率增加，啤酒花提取物导致丙酸与乙酸的比例增加。啤酒花提取物抑制了牛链球菌的生长和代谢，但对反刍月形单胞菌和巨球形梭菌没有影响。同样，在啤酒花提取物存在的情况下，M. elsdenii/S. bovis 共培养物的丙酸产量下降，但 M. elsdenii/S. ruminantium 共培养物的丙酸产量没有下降。
这些结果与啤酒花抑制革兰氏阳性乳酸杆菌（S. bovis）的假设一致，瘤胃微生物群落需要一段时间的适应才能恢复正常的 VFA 生产。牛链球菌和反刍月形单胞菌都产生乳酸，这是巨球形梭菌产生丙酸的底物。然而，反刍月形单胞菌有外膜，而牛链球菌没有。
作为糖异生前体的丙酸产量增加，进一步证明了啤酒花中的植物次生代谢产物可用于改善瘤胃发酵。
