Microbial growth at reduced water activities: some physicochemical properties of compatible solutes

Abstract

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.'

Compatible Solutes Protect against Chaotrope(Ethanol)-Induced, Nonosmotic WaterStress

“…Glycerol and erythritol enhance conidial germination of several fungal species under NaCl-induced osmotic stress (8) and also have this effect on A. nidulans (Table 2). In contrast, mannitol is relatively ineffective as an osmoprotectant (2,4,7,8).…”

The water relations of growth and polyhydroxy alcohol production by ascomycetous yeasts

“…As an osmolyte, glycerol offers a number of advantages : high glycerol concentrations confer a remarkable degree of protection to enzymes and macromolecular structure , and modification of proteins is unnecessary in order to function in concentrated intracellular solutions. Furthermore, the solubility and viscosity of glycerol are hardly affected by increasing concentrations of this polyol (Chirife et al, 1983(Chirife et al, , 1984.…”

The Latest on Sugar Substitutes of the Alditol Type with Special Consideration of Erythritol and Xylitol―Rectifications and Recommendations

“…Therefore, alditols do not behave similarly in their reactions with water molecules. The predicted and experimental water activity levels also depended on the molality of the aqueous alditol solution, as shown for xylitol and ribitol [66]. Furthermore, the average non-dimensional free energy and volume parameters greatly depended on the alditol in question [66].…”

“…The predicted and experimental water activity levels also depended on the molality of the aqueous alditol solution, as shown for xylitol and ribitol [66]. Furthermore, the average non-dimensional free energy and volume parameters greatly depended on the alditol in question [66]. The hydration number is a measure of the number of water molecules that have a relatively long residence time with the solute and hence tend to move with it rather than with bulk water [67].…”

“…However, at the same time the alditol molecules, by virtue of their high number of OH groups can participate in the intracellular water structure, thereby preserving the hydration of the cellular biopolymers [65]. Based on these considerations, Chirife et al [66] determined the water activity (a w ) levels of several alditols from the following equation:…”