Abstract
BackgroundOptimization 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.MethodsThe 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.ResultsThe 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.ConclusionsThis 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.
Highlights
Optimization of the unsaturated fatty acid composition of ruminant milk and meat is desirable
Metabolism of trans-vaccenic acid to stearic acid t-VA enrichment cultures were obtained through numerous transfers (n = 8) into fresh medium containing t-VA (50 μg mL-1), whereas cultures without t-VA served as the control group
Incubation was performed at 39°C, and the accumulation of SA as the main metabolism product in the culture and concentration of tVA as substrate was collected at each transfers (Figure 1)
Summary
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. As the consumption of dairy products and ruminant meats is often associated with an increased incidence of coronary heart disease [1] (Menotti and Kromhout et al, 1999), the transformation of unsaturated fatty acids to saturated fatty acids, or biohydrogenation, in ruminants represents a major human health issue. Microbial biohydrogenation is the process of converting unsaturated fatty acids to more saturated end products by gut microbes. Kemp and Lander [7] (1984) divided ruminal bacteria into two groups based on the reactions and end products of biohydrogenation. Group A bacteria were able to hydrogenate linoleic acid and linolenic acid, with tVA being their major end product. Group B bacteria utilized t-VA as one of the main substrates with SA being the end product
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