EFFECT OF GASEOUS ENVIRONMENT AND TEMPERATURE ON ASCOSPORE FORMATION IN SACCHAROMYCES CEREVISIAE HANSEN

Abstract

The effect on ascospore formation in bakers' yeast of varying degrees of aeration and of oxygen, carbon dioxide, and nitrogen individually and in mixtures was studied. In the absence of carbon dioxide, ascospore formation was stimulated by concentrations of oxygen up to 12.0% but was depressed slightly at 41.1% and more so at 68.8% and at 100%. Carbon dioxide inhibited ascospore formation; very few were found when the carbon dioxide concentration was 25% or greater. Oxygen did not overcome the inhibitory effect of carbon dioxide. Ethyl alcohol vapor so markedly inhibited sporulation that ascospores were rarely observed in cultures exposed to the vapor from a 5% solution of ethyl alcohol. Ascospore formation was observed at. temperatures from 3.0 to 33.3 °C. Of two strains studied in one experiment, one showed highest sporulation at 24.0 °C. and the other at 27.5 °C. Cells exposed for 14 days to temperatures of 2.5, −3.5, and −18.0 °C, and cells multiplied at 37.5 °C, showed reduced sporulation at room temperature.