SELECTIVESACCHAROMYCESMEDIA CONTAINING ERGOSTEROL AND TWEEN 80

Abstract

A mixture (ET80) of ergosterol and Tween 80 stimulated the anaerobic growth on solid media of almost all strains of Saccharomyces tested. Yeasts from other genera have only produced micro-colonies. It is possible to detect Saccharomyces yeasts after 40 h anaerobic incubation and subsequently to estimate total infection after a further 24 h aerobic incubation. Saccharomyces contaminants can be differentiated from other yeasts and from bacteria within 24 h by a simple staining procedure using malachite green. Anaerobic incubation for 4 days on ET80-supplemented crystal violet agar is selective for wild Saccharomyces only, thus allowing a clear differentiation between lysine-positive and lysine-negative yeasts. This medium is suitable for use with membrane filter-discs.