Heat-shock and ethanol-osmotic effect on fermentable yeast cells

This study investigated the effect of heat and ethanol on fermentable yeast cells. Fermentable yeast cells (Saccharomyces cerevisiae strains and non-saccharomyces species) were subjected to varying temperature (37, 40 and 44°C) and ethanol concentration (8, 10, 14 and 18%) respectively. In the research, 55.35% of the fermentable yeasts were highly thermotolerant, moderately thermotolerant (42.86%), slightly thermotolerant (1.79%) while the industrial strain was non-thermotolerant. With respect to ethanol osmotic shock effect, 41.07% were highly tolerant, moderately tolerant (58.93%) while none was slightly or non-tolerant. Thus, there was significant difference in biomass yield obtained at different temperatures and ethanol concentrations. Furthermore, the flocculation analysis showed that 80% of the yeast cells were highly flocculant, slightly flocculant (13%) and non-flocculant (7%) respectively. Summarily, exposure of yeast cells to elevated temperatures and ethanol concentrations increase ability of cells to survive exposure to lethal heat and ethanol osmotic shock during ethanol production.