Kim Young Jun
Department of Molecular Biology and Genetics, Biotechnology Building, Cornell University, Ithaca, New York 14583-2703, USA.
J Agric Food Chem. 2003 Jul 16;51(15):4258-62. doi: 10.1021/jf034057r.
Butyrivibrio fibrisolvens A38, one of the most active rumen bacteria in conjugated linoleic acid (CLA) production, was characterized in vitro. Previous findings that some inhibitory levels of substrate for biohydrogenation (BH) by B. fibrisolvens A38 resulted in more CLA accumulation led to a prediction that partial inhibition of BH could increase ruminal CLA production. The inhibitory conditions for bacterial growth were less effective on the isomerization step than on the following reduction step. Linoleic acid (LA) was inhibitory not only to cell growth but also to LA hydrogenation, and this effect was greater at high concentrations. The reduction step, converting CLA to hydrogenated products (trans-C18:1 and C18:0), was significantly inhibited, and more CLA accumulated during aerobic incubation when LA was added along with a glycolytic inhibitor, iodoacetate (IAA), to cells that were pre-adapted to LA (1 g/OD at 600 nm/L, P < 0.05). Monensin was more inhibitory than IAA to cell growth but less effective for CLA accumulation. Rumen fluid in the culture medium appeared to activate BH even in an aerobic condition, resulting in a lower CLA level than the control group (P < 0.05). Because the isomerization and reduction steps are coupled reactions in BH of most hydrogenating bacteria including B. fibrisolvens A38 cells, both positive and negative modulations of the reduction steps could be key determinants for CLA accumulation in the rumen.
