In vitro synthesis of conjugated linoleic acids by rumen bacteria
2007
Kawahara, S.(Miyazaki Univ. (Japan). Faculty of Agriculture) | sakka, K. | Niimi, M. | Kawamura, O. | Muguruma, M.
The objective of this study was to develop a method for selective preparation of cis-9, trans-11 conjugated linoleic acid (c9, t11 CLA) by use of rumen bacterial culture. Rumen bacteria cultured in a medium containing sodium linoleate or free linoleate as a precursor at 38 deg C for 3 hours successfully produced c9, t11 CLA in the culture medium. On the other hand, trilinoleate was not satisfactory precursor for c9, t11 CLA preparation by rumen bacteria. A small amount of trans-10, cis-12 CLA (t10, c12 CLA) was also produced by the culture. Although c9, t11 CLA produced was gradually saturated to trans-vaccenic acid (t-vaccenic acid), t10, c12 CLA remained increasing. These results suggest that cis-9 double bond of c9, t11 CLA might be saturated by deltasup(9)-saturase expressed on rumen bacteria. For selective production of c9, t11 CLA, pH of culture medium was important. When rumen bacteria cultured in acidic pH conditions (from pH 6.0 to 7.0), t10, c12 isomer was predominantly produced, whereas c9, t11 isomer was preferentially produced in high pH conditions (i.e., pH 7.5 to 8.0). In addition, large amount of t-vaccenic acid was produced in low pH conditions. Therefore, acceleration of saturation of the CLA by rumen bacteria in lower pH might cause the lower yield of c9, t11 CLA. The present results suggest that the c9, t11 CLA production by use of rumen bacteria requires satisfactory precursors and regulating saturation of c9, t11 CLA.
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