BIOHYDROGENATION OF UNSATURATED FATTY ACIDS BY RUMEN BACTERIA

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Abstract
A simple, rapid, specific assay for the biohydrogenation of unsaturated fatty-acids was developed. With this assay, it was shown that washed suspensions of mixed rumen bacteria hydrogenate linoleic-and oleic-acids. Butyrivibrio fibrisolvens, a common rumen bacterium, is capable of hydrogenating linoleic-acid to octadecenoic-acid but not to stearic-acid. Complete anaero-biosis is required, and with mixed rumen bacteria more activity is obtained in an atmosphere of hydrogen than of either nitrogen or helium, whereas carbon-dioxide is inhibitory. The extent of biohydrogenation varies with the season of the year, and a variable stimulatory effect is obtained upon the addition of boiled rumen fluid. Biohydrogenation activity in B. fibrisolvens is markedly dependent upon the age of the organism and concentration of cells used in the medium. The presence of certain other rumen bacteria, which by themselves are incapable of carrying out the biohydrogenation reaction, can prevent loss of activity of B. fibrisolvens due to age or dilution. Two systems are involved in the complete hydrogenation of linoleic-acid one specific for the conversion of linoleic-acid to a monoenoic acid, and the other for the hydrogenation of a monoenoic acid to stearic-acid.