Li Dan, Wang Jia Qi, Bu Deng Pan
State Key Laboratory of Animal Nutrition, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, 00193, PR China.
BMC Res Notes. 2012 Feb 15;5:97. doi: 10.1186/1756-0500-5-97.
Optimization of the unsaturated fatty acid composition of ruminant milk and meat is desirable. Alteration of the milk and fatty acid profile was previously attempted by the management of ruminal microbial biohydrogenation. The aim of this study was to identify the group of ruminal trans-vaccenic acid (trans-11 C18:1, t-VA) hydrogenating bacteria by combining enrichment studies in vitro.
The enrichment culture growing on t-VA was obtained by successive transfers in medium containing t-VA. Fatty acids were detected by gas chromatograph and changes in the microbial composition during enrichment were analyzed by denaturing gradient gel electrophoresis (DGGE). Prominent DGGE bands of the enrichment cultures were identified by 16S rRNA gene sequencing.
The growth of ruminal t-VA hydrogenating bacteria was monitored through the process of culture transfer according to the accumulation of stearic acid (C18:0, SA) and ratio of the substrate (t-VA) transformed to the product (SA). A significant part of the retrieved 16S rRNA gene sequences was most similar to those of uncultured bacteria. Bacteria corresponding to predominant DGGE bands in t-VA enrichment cultures clustered with t-VA biohydrogenated bacteria within Group B.
This study provides more insight into the pathway of biohydrogenation. It also may be important to control the production of t-VA, which has metabolic and physiological benefits, through management of ruminal biohydrogenation bacterium.
优化反刍动物奶和肉中的不饱和脂肪酸组成是很有必要的。之前曾尝试通过瘤胃微生物生物氢化作用来改变奶和脂肪酸的组成。本研究的目的是通过体外富集研究相结合的方法来鉴定瘤胃反式-11-十八碳烯酸（反式-11 C18:1，t-VA）氢化细菌群。
通过在含有t-VA的培养基中连续传代获得以t-VA为生长底物的富集培养物。用气相色谱法检测脂肪酸，并通过变性梯度凝胶电泳（DGGE）分析富集过程中微生物组成的变化。通过16S rRNA基因测序鉴定富集培养物中显著的DGGE条带。
根据硬脂酸（C18:0，SA）的积累以及底物（t-VA）转化为产物（SA）的比例，在培养物传代过程中监测瘤胃t-VA氢化细菌的生长情况。检索到的16S rRNA基因序列中有很大一部分与未培养细菌的序列最为相似。t-VA富集培养物中与主要DGGE条带对应的细菌与B组中的t-VA生物氢化细菌聚集在一起。
本研究为生物氢化途径提供了更多见解。通过管理瘤胃生物氢化细菌来控制具有代谢和生理益处的t-VA的产生也可能很重要。
