Examining the Role of Membrane Lipid Composition in Determining the Ethanol Tolerance of Saccharomyces cerevisiae

Abstract

Yeast (Saccharomyces cerevisiae) has an innate ability to withstand high levels of ethanol that would prove lethal to or severely impair the physiology of other organisms. Significant efforts have been undertaken to elucidate the biochemical and biophysical mechanisms of how ethanol interacts with lipid bilayers and cellular membranes. This research has implicated the yeast cellular membrane as the primary target of the toxic effects of ethanol. Analysis of model membrane systems exposed to ethanol has demonstrated ethanol's perturbing effect on lipid bilayers, and altering the lipid composition of these model bilayers can mitigate the effect of ethanol. In addition, cell membrane composition has been correlated with the ethanol tolerance of yeast cells. However, the physical phenomena behind this correlation are likely to be complex. Previous work based on often divergent experimental conditions and time-consuming low-resolution methodologies that limit large-scale analysis of yeast fermentations has fallen short of revealing shared mechanisms of alcohol tolerance in Saccharomyces cerevisiae. Lipidomics, a modern mass spectrometry-based approach to analyze the complex physiological regulation of lipid composition in yeast and other organisms, has helped to uncover potential mechanisms for alcohol tolerance in yeast. Recent experimental work utilizing lipidomics methodologies has provided a more detailed molecular picture of the relationship between lipid composition and ethanol tolerance. While it has become clear that the yeast cell membrane composition affects its ability to tolerate ethanol, the molecular mechanisms of yeast alcohol tolerance remain to be elucidated.

Chaotropicity: a key factor in product tolerance of biofuel-producing microorganisms

“…In ABE fermentations, solventogenic Clostridium species respond to chaotropes pleiotropically by expressing heat-shock protein genes, modifying the proportion of unsaturated fatty acids in the cell membrane and producing more carboxylic acids such as acetic and butyric acids to generate more ATP [9]. Comparable responses to ethanol stress are observed in S. cerevisiae upon exposure to ethanol [73]. While substrate-level phosphorylation resulting in production of acetic and butyric acids is a major channel by which solventogenic Clostridium species generate ATP, excesses of these acids can be inhibitory to the cells unless efficiently disposed of via solventogenesis (Table 2) [9].…”

Evidence for a Role for the Plasma Membrane in the Nanomechanical Properties of the Cell Wall as Revealed by an Atomic Force Microscopy Study of the Response of Saccharomyces cerevisiae to Ethanol Stress

“…These inhibitory and toxic effects are ascribed to the fact that ethanol alters cell membrane fluidity and dissipates the transmembrane electrochemical potential, thereby creating permeability to ionic species and causing leakage of metabolites (2). Recent works using lipidomic methodologies confirmed the relationship between the composition of lipids, notably ergosterol and unsaturated fatty acids, and ethanol tolerance (3,4). Moreover, as it diffuses freely into cells, ethanol at high concentrations may directly perturb and denature intracellular proteins (reviewed in references 5 and 2).…”

“…Altogether, and regardless of how tolerance to ethanol was defined (2), these genome-scale studies underscored the genetic intricacy of ethanol tolerance and the complexity of the yeast response to this compound at the molecular level. However, these studies did not bring us any clue about the physical effects that ethanol can have on yeast cells, although some transcriptomic and metabolomic data may suggest important modifications of cellular membranes (3,4,(17)(18)(19)(20) and cell wall organization (12) of yeast cells exposed to high levels of ethanol. Thus, obtaining biophysical data on yeast cells exposed to high ethanol concentrations may provide complementary information on how cells can cope with this toxic compound, which may be relevant for further strategies to improve the tolerance of yeast toward ethanol.…”

Evaluation of behaviour ofLachancea thermotoleransbiocontrol agents on grape fermentations

“…() mentioned that L. thermotolerans presented a high fermentation power (10·46%). The discrepancy between the results on tolerances may be explained by differences in the plasma membrane fluidity, integrity of strains assayed (Henderson and Block ) or by the strain variability in the fermentation power (Comitini et al . ).…”