Sterol metabolism of micro-organisms

Abstract

Baker''s yeast was grown for 1-3 days on eane-sugar plus phosphate medium, aerobically and anaerobically. Sterol formation was measured spectrographically and sometimes by the digitonide method. The effect on the amt. of sterol formed by a number of possible intermediates was estimated; the effect of varying cultural conditions was also studied. Na acetate led to a slight increase; ascorbic acid an increase in one case and not in others; hydrolyzed yeast glycogen and ethyl alcohol were ineffective. Mixed amino-acids, tyrosine and tyrosol respectively tended to inhibit sterol formation. Sterol formation is a feature of aerobic metabolism, arises early in the course of fermentation, is not directly correlated with growth and is mostly esterified.