Production of menaquinones by lactic acid bacteria.

Lactic acid bacteria were examined for their ability to produce quinone compounds, which may include dietary sources of menaquinones. Isoprenyl quinones in bacterial cells grown in a synthetic medium were extracted and analyzed by thin layer chromatography. Lactococcus lactis ssp. cremoris (three strains), Lactococcus lactis ssp. lactis (two strains), and Leuconostoc lactis were selected as high producers of quinone that synthesized more than 230 nmol of quinones/g of dried cells. The quinones were presumed to be menaquinone-7 to -10 by high performance liquid chromatography. Precise molecular weights were determined by mass spectrometry for Lactococcus lactis ssp. cremoris YIT 2011 and Leuconostoc lactis YIT 3001 and identified as menaquinone-8 and -9 for the former and menaquinone-9 and -10 for the latter. Those strains, when grown either in reconstituted nonfat dry milk or a soymilk medium, produced a beneficial quantity for dietary supplement (i.e., 29 to 123 micrograms of menaquinones/L of the fermented medium).