Permeability and membrane sterol distribution in Saccharomyces uvarum and Kluyveromyces bulgaricus grown in presence of polyoxyalkylene glycol-oleic acid condensates

Summary Antifoam agents, such as polyoxyalkylene glycol-oleic acid condensates, increase cell permeability in Saccharomyces uvarum, but decrease cell permeability in Kluyveromyces bulgaricus.In S. uvarum it was found that the increase in cell permeability is related to a significantly higher level of total sterols. In K. bulgaricus, in which a decrease of permeability was observed, the overall level of sterols is lower.Determination of the sterol derivatives showed that in S. uvarum the content of all sterols identified was increased; in K. bulgaricus only the ergosterol content was increased. The difference in behaviour of the two yeasts grown in the presence of antifoam agents could be attributed to an effect of these agents on sterol biosynthesis.