Effect of linoleic acid concentration on conjugated linoleic acid production by Butyrivibrio fibrisolvens A38

Butyrivibrio fibrisolvens A38 inocula were inhibited by as little as 15 muM linoleic acid (LA), but growing cultures tolerated 10-fold more LA before growth was inhibited. Growing cultures did not produce significant amounts of cis-9, trans-11 conjugated linoleic acid (CLA) until the LA concentratio n was high enough to inhibit biohydrogenation, growth was inhibited, and ly sis was enhanced. Washed-cell suspensions that were incubated anaerobically with 350 muM LA converted most of the LA to hydrogenated products, and lit tle CLA was detected. When the washed-cell suspensions were incubated aerob ically, biohydrogenation was inhibited, CLA production was at least twofold greater, and CLA persisted. The LA isomerase reaction was very rapid, but the LA isomerase did not recycle like a normal enzyme to catalyze more subs trate. Cells that were preincubated with CLA lost their ability to produce more CLA from LA and the CLA accumulation was directly proportional (r(2) = 0.98) to the initial cell density. Growing cells were as sensitive to CLA as LA the LA isomerase and reductases of biohydrogenation were Linked, and free CLA was not released. Because growing cultures of B, fibrisolvens A38 did not produce significant amounts of CLA until the LA concentration was h igh, biohydrogenation was arrested, and the cell density had declined, the flow of CLA from the rumen may be due to LA-dependent bacterial inactivatio n, death, or lysis.