Yeast membrane adaptation during fermentation

Yeast membrane adaptation during fermentation

Adaptation of yeasts to changing environments experienced during biomass propagation and ethanolic fermentation for biofuel requires rapid modulation of membrane fluidity. We applied fluorescence spectroscopy and microscopy to investigate yeast cell membrane and physiological responses to such changing environments. Our investigations included development and adaptation of methodology to assess membrane fluidity of yeasts, and has shown that membrane fluidity relates to growth phase, cellular physiology and nutrition as well as to membrane lipid and protein composition. We found that membrane responses to glucose depend on particular membrane proteins. Furthermore our studies have shown that rather than the commonly held view of membrane fluidization, heat damage of membranes leads to lower membrane fluidity, likely due to membrane protein denaturation. In addition, we investigated membrane responses to fluidization by high ethanol concentrations. While other studies indicated that higher membrane fluidity or unsaturated fatty acid content correlated with improved ethanol tolerance, we found the opposite, that the fluidizing effects of ethanol were minimized by decreased membrane fluidity, leading to higher ethanol tolerance. The roles of various cellular factors on these adaptive responses will be discussed.

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