No abstract

Sum ma ryA systematic survey was made of water activity reduction in single non electrolyte aqueous solutions together with an examination of the theoretical aspects of a, predictions. The prediction of a, in multicomponent aqueous solutions of non electrolytes as well as of mixed strong electrolyte-non electrolyte solutions was also studied.

The water activities (aw) of solutions of D-arabitol (a major compatible solute in yeasts grown at reduced aw) and also of related polyols (L-arabitol, xylitol and ribitol) were determined at 25 degrees C. The aw of saturated solutions of L-proline and monopotassium L-glutamate (solutes which accumulate in bacterial cells at reduced aw) were also determined. The viscosities of L-proline, monopotassium L-glutamate and D-arabitol solutions were measured at 25, 30, 35 and 40 degrees C for various concentrations up to high molalities. The relative viscosity curves were described using a theoretical model for the concentration dependence of viscosity. No relationship of viscosity of the electrolytes to effectiveness as 'compatible solutes' were evident, neither were the compatible solutes particularly effective 'structure makers' or 'structure breakers.'