title: Biohydrogenation of linolenic acid to stearic acid by the rumen microbial population yields multiple intermediate conjugated diene isomers.
abstract: The current literature suggests that linolenic acid biohydrogenation converts to stearic acid without the formation of CLA. However, a multitude of CLA were identified in the rumen that are generally attributed to linoleic acid biohydrogenation. This study used a stable isotope tracer to investigate the biohydrogenation intermediates of (13)C-linolenic acid, including CLA. A continuous culture fermenter was used to maintain a mixed microbial population obtained from the rumen of cattle at pH 6.5 for 6 d. The mixed fermenter contents were then transferred to batch cultures containing either (13)C-labeled or unlabeled linolenic acid, which were run in triplicate for 0, 3, 24, and 48 h. The (13)C enrichment was determined by GC-MS. After 48 h of incubation, 8 CLA isomers were significantly enriched, suggesting that these CLA isomers originated directly from linolenic acid. The cis-10, cis-12 CLA isomer exhibited the highest enrichment (21.7%), followed by cis-9, cis-11 and trans-8, trans-10 CLA. The enrichment of these 2 CLA isomers ranged from 20.1 to 21.1% and the remaining 5 CLA including cis-9, trans-11 CLA were <15.0%. A multitude of nonconjugated and partially conjugated 18:2 and 18:3 isomers was enriched during the 48 h of incubation. The results of this study confirm that mixed ruminal microbes are capable of the formation of several CLA and 18:3 isomers from linolenic acid, indicating that linolenic acid biohydrogenation pathways are more complex than previously reported.
authors.affiliation: Department of Animal and Veterinary Sciences, Clemson University, Clemson, SC 29634, USA.
authors.forename: Yong-Jae
authors.initials: YJ
authors.lastname: Lee
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Jenkins
mesh_terms: D000818:Animals; D002417:Cattle; D005285:Fermentation; D008401:Gas Chromatography-Mass Spectrometry; D006859:Hydrogen / Q000378:metabolism*; D007536:Isomerism; D013229:Stearic Acids / Q000378:metabolism*; D017962:alpha-Linolenic Acid / Q000737:chemistry / Q000378:metabolism*
chemical_list: D013229:Stearic Acids; D017962:alpha-Linolenic Acid; C031183:stearic acid; D006859:Hydrogen