Factors influencing deactivation of yeast cells exposed to ethanol.

The lyotropic series discovered in 1888 by Hofmeister describes the effect of solutes on the structure and physical chemistry of the aqueous phase. Chaotropic members of the lyotropic series destructure the aqueous phase while antichaotropic solutes act to enhance the structuredness of the aqueous phase. This alteration of the aqueous phase affects the physical structure or physicochemical state of any other phase exposed to the aqueous phase, such as the plasma membrane of any cell. Solute lyotropy is therefore, via its ability to alter the physicochemical state of the plasma membrane, able to modify the processes of yeast cell deactivation (i.e. the processes leading to loss of ability to replicate and to eventual cell death) in the presence of toxic solutes such as ethanol. In this study the effect of a variety of salts and non-ionic solutes upon cell deactivation in the presence of 16% w/v ethanol is explained in terms of the lyotropic series. Chaotropic salts protect against ethanol-induced deactivation and antichaotropic salts enhance the rate of this process. It is proposed that the mechanism by which chaotropic solutes exert their protective effect involves a reduction in the activity coefficient of the ethanol, thereby reducing the concentration of ethanol within the plasma membrane.