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Studies on the production of conjugated linoleic acid from linoleic and vaccenic acids by mixed rumen protozoa


The present study was designed to investigate the capability of mixed rumen protozoa to synthesize conjugated linoleic acid (CLA) from linoleic (LA) and vaccenic acids (VA). Rumen contents were collected from fistulated cows. The protozoal fraction was separated and washed several times with MB9 buffer and then resuspended in autoclaved rumen fluid. The suspensions were anaerobically incubated up to 18 h at 38.5 °C with substrates in the presence (P-AB) or the absence of antibacterial-agents (P-No-AB). Neither P-AB nor P-No-AB suspensions were capable of producing CLA from VA (11t-18:1). Linoleic acid was catabolized by P-No-AB to a greater extent than P-AB. Different isomers of CLA were synthesized by P-AB from LA. The 9c11t-CLA was predominant. Thirty seven percent of the maximum accumulated 9c11t-CLA was found in the P-AB suspension as early as 0.1 h into the incubation period. Accumulation of 10t12c-CLA in P-AB suspension was approximately 10.0 times lower than that of 9c11t-CLA. There were no significant productions of VA, 10t-18:1, and 18:0 in P-AB compared with the control, indicating that rumen protozoa have no ability to biohydrogenate CLA isomers. On the other hand, the concentrations of 10t-18:1, VA, and 18:0 in P-No-AB were greater (P < 0.05) compared with those in P-AB, indicating the role of symbiotic bacteria associated with P-No-AB in biohydrogenating CLA isomers. We concluded that mixed rumen protozoa are capable of synthesizing CLA from LA through isomerization reactions. However, they are incapable of metabolizing CLA further. They are also incapable of vaccenic acid biohydrogenation and/or desaturation.

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The authors would like to thank the staff at the Elora Dairy Research Centre (University of Guelph, ON, Canada) for their technical assistance. We would also like to acknowledge the continued support received from the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) and the Natural Sciences and Engineering Research Council of Canada (NSERC).

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Correspondence to Brian W. McBride.

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Or-Rashid, M.M., AlZahal, O. & McBride, B.W. Studies on the production of conjugated linoleic acid from linoleic and vaccenic acids by mixed rumen protozoa. Appl Microbiol Biotechnol 81, 533–541 (2008).

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  • CLA
  • Rumen protozoa
  • Linoleic acid
  • Vaccenic acid