VARIATIONS IN THE CONTENT OF ERGOSTEROL AND ITS triangleopen~(5,7) PRECURSORS DURING GROWTH OF SACCHAROMYCES CEREVISIAE WITH ETHANOL AT HIGH AND LOW AVAILABILITY OF NITROGEN

摘要

During the batch growth of Saccharomyces cerevisiae D7 on ethanol, variations in the content of free and esterified ergosterol and two ergosterol precursors, ergost-5,7,22,24(28)-tetra-3beta-ol and ergost-5,7-dien-3|3-ol, were investigated under the conditions of excess nitrogen and nitrogen limitation. In both types of culture, the dominant DELTA~(5,7)sterol was ergosterol. With nitrogen limitation, esteri-fied DELTA~(5,7) sterols were dominant in the yeast cells. With a nitrogen-rich culture medium, the degree of DELTA~(5,7) sterol esterification, especially that of ergosterol and ergost-5,7-dien-3beta-ol, decreased, which began with the entry into the exponential growth phase and lasted until the entry into the stationary phase. Excess carbon compared to nitrogen in the medium favoured an increased accumulation of sterols in the yeast cells (and the accumulation of the ergosterol precursor, ergost-5,7,22,24(28)-tetra-3beta-ol, in particular), both in free and esterified forms.