Characterization of Sterol Lipids in Kluyveromyces lactis Strain M-16 Accumulating a High Amount of Steryl Glucoside

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Kluyveromyces lactis strain M-16 isolated from raw milk accumulates a high amount of steryl glucoside in the cells. Under high temperature or in the presence of NaCl, this strain did not show better growth than other K. lactis strains that hardly accumulated steryl glucoside. Heat shock elevated the content of steryl glucoside 3.2-fold, which accounted for 27% of the total sterol lipids, and simultaneously reduced that of acyl sterol. Both strains, M-16 and NBRC 1267, contained ergosterol as a principal component, and dihydroergosterol was also included in steryl glucoside of strain M-16. Lanosterol was a major component second to ergosterol in free sterols. In acyl sterol of strain M-16, the proportion of 4,4-dimethylzymosterol was higher than that of ergosterol. Excess synthesis of steryl glucoside in strain M-16 consumes ergosterol and dihydroergosterol in the pool of free sterols, and acyl sterol may inevitably take in 4,4-dimethylzymosterol and 4-methylfecosterol, the intermediates in the biosynthetic pathway to ergosterol, as a component sterol.