Ethanol tolerance of yeast

The ethanol tolerance mechanism in yeasts is not very well understood. This may result from the complex inhibitory mechanisms of ethanol, the lack of a universally accepted definition and method to measure ethanol tolerance, and its complex polygenic characteristic. Recently, there has been some progress in understanding ethanol tolerance. Plasma membrane phospholipids have been shown to play an important role in the ethanol tolerance mechanism. Increases in membrane unsaturated fatty acids result in increased yeast ethanol tolerance. Supplementation of growth media with combinations of unsaturated fatty acids, vitamins and proteins also enhance ethanol tolerance. Physiological factors such as mode of substrate feeding, intracellular ethanol accumulation, temperature and osmotic pressure all contribute to the ethanol tolerance of yeast. The complex nature of ethanol toxicity suggests that a number of different genes are likely to be involved in the ethanol tolerance mechanism. Genetic approaches such as spheroplast or protoplast fusion, hybridization and continuous culture selection have been used to obtain ethanol tolerant yeasts. Isolation and characterization of such strains may provide a better understanding of ethanol tolerance.