Hydrogenation of C18 Unsaturated Fatty Acids by Pure Cultures of a Rumen Micrococcus

Abstract

Approximately 70% of the fatty acids present in plant lipids are unsaturated; the major component is cis-9,cis-12,cis-15-octadecatrienoic acid (Garton 1963). After ingestion by ruminants, these acids are readily hydrogenated by microorganisms in the rumen to form a complex mixture of positional and geometrical C18 isomers (Shorland et al. 1957;Ward, Scott, and Dawson 1964;Wilde and Dawson 1966;Kemp and Dawson 1968). Kemp and Dawson (1968) showed that the first stage in the hydrogenation of linolenic acid by a mixed population of washed rumen microorganisms was an isomerization to form a conjugated triene, cis-9,trans-ll,cis-15-octadecatrienoic acid. This acid was identified by Kepler and Tove (1967) after pure cultures of Bmyrivibrio fibrisolvens were incubated with linolenic acid. These authors also showed that this conjugated triene was hydrogenated to a non-conjugated diene, which from its retention time on gas-liquid chromatography had at least one trans double bond. However, in these experiments, no further hydrogenation of the diene was detected. Wilde and Dawson (1966) incubated linolenic acid with pure cultures of several bacteria found in the rumen and only B. fibrisolvens and Escherichia coli possessed any hydrogenating activity and the intermediary products were not studied in detail. Recently, Kemp and White (1968) briefly reported the isolation from the rumen of three species of anaerobic bacteria which could hydrogenate linolenic and linoleic acids to monoenoic acids. The present studies were undertaken to extend our knowledge of the process of hydrogenation and to identify the products formed during the metabolism of linolenic and linoleic acids by pure cultures of a rumen micrococcus. A preliminary report of this work has already been published (Mills et al. 1969). Experimental (a) I80lation and Incubation of the Micrococcus with [14C]Fatty Acid8Cultures of the rumen miorooooous were isolated from rumen oontents by prooedures outlined previously (Russell and Smith 1968). The organism was inoubated for 24 hr at 38°C under anaerobio oonditions, in oarbon dioxide, in a medium desoribed by Russell and Smith (1968) oontaining [14C]fatty aoid (5 p.Ci, 0·1 p.mole) oomplexed to bovine serum albumin (Kessler, Demeny, and Sobotka 1967, method B). Vessels oontaining boiled suspensions of the miorooocous were prepared as controls for each acid.

Hydrogenation of Unsaturated Fatty Acids by Treponema ( Borrelia ) Strain B 2 5, a Rumen Spirochete

“…For this reason, it has been difficult to characterize the reactions involved in the hydrogenation process. Several rumen bacteria have been identified as possessing the ability to hydrogenate 18-carbon, unsaturated fatty acids (19,21,23,28); however, only Butyrivibrio fibrisolvens strain A38 has been studied in detail (13,14,16). A particulate isomerase from this bacterium initially isomerizes linoleic acid to cis-9, trans-11-octadecadienoic acid.…”

Structural Analysis of Conjugated Linoleic Acid Produced byLactobacillus plantarum, and Factors Affecting Isomer Production

“…The chemical structure of CLA1 was not identiˆed: it may be cis-9,trans-11-or trans-9,cis-11-18:2. 5-7) Some studies found that linoleic acid is converted to 9,11-18:2 by several species of rumen bacteria [8][9][10][11][12][13][14][15] and by dairy starter cultures. 16) However, to our knowledge, exact identiˆcation of the geometric conˆguration of the 9,11-18:2 produced has not been done.…”

The composition and stability of lipids in meat products and a spectrofluorometric assay for malonaldehyde in biological tissues

“…The ability of microwave energy to cause Isomerlzation of fatty acids in other foods needs to be studied. Rumen micrococci have been shown to cause isomerlzation of fatty acids (Mills et al, 1970). A species of Micrococcus is used as a starter culture in the preparation of summer sausages.…”