Five
Lactobacillus strains (2
L. gasseri, 2
L. plantarum and 1
L. reuteri) were cultured in modified MRS medium containing fatty acids (FAs) instead of Tween 80 for 24 h at 37°C, to learn the effect of saturated and unsaturated FAs on the
Lactobacillus growth. Free FAs included palmitic (16:0), palmitoleic (
c9-16:1), stearic (18:0), oleic (
c9-18:1), elaidic (
t9-18:1),
cis-vaccenic (
c11-18:1), vaccenic (
t11-18:1), linoleic (
c9,
c12-18:2), conjugated linoleic (
c9,
t11- and
t10,
c12-18:2), α-linolenic (
c9,
c12,
c15-18:3), α-eleostearic (
c9,
t11,
t13-18:3), eicosapentaenoic (20:5), and docosahexaenoic (22:6) acids. Among free FAs, oleic acid stimulated the growth of all
Lactobacillus strains, whereas palmitoleic acid had almost no affect on the
Lactobacillus growth. Saturated FAs such as stearic and palmitic acids inhibited or did not affect the
Lactobacillus growth. Polyunsaturated FAs such as α-linolenic, eicosapentaenoic and docosahexaenoic acids strongly inhibited the
Lactobacillus growth at 7.6×10
−4 m. Octadecenoic acids such as oleic, elaidic,
cis-vaccenic and vaccenic acids remarkably promoted the growth of
L. gasseri, regardless of the different double bond positions and configurations. When oleic or
cis-vaccenic acid was incubated with
L. gasseri, the FAs was transformed to cyclopropane FAs (methyleneoctadecanoic acids) after incorporation into the cells. On the other hand,
trans FAs such as elaidic and vaccenic acids incorporated into the cells were not converted to another FAs. Conjugated linoleic and α-eleostearic acids having a
trans double bond promoted the
Lactobacillus growth. The growth of
L. gasseri was also stimulated by
trans-rich free FAs from hydrogenated canola and fish oils. These results showed that octadecenoic acid and
trans FAs had strong promotion activities for the
Lactobacillus growth due to their incorporation into membrane lipids.
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