Yeast thermal stress

An interesting illustration of the roles played by low-molecular-mass protein stabilizers in assisting cells to cope with heat stress is provided by work of Singer and Lindquist (1998a,b), who examined the complementary roles of the disaccharide trehalose and heat-shock proteins in recovery from thermal stress by the yeast Saccharomyces cerevisiae. Many types of yeast produce high concentrations of... 

Yeast cells Saccharomyces cerevisiae) are surrounded by a membrane protecting the inside from evaporation or oxidation. This membrane can be reversibly permeabilized by immersion in a hypotonic NaCl solution. The holes created in the membrane allow the loading of a molecule in the cell, according to the method of Bishop. Chlorogenic acid or curcmnin have been encapsulated in yeast cells, leading to a better stability of the encapsulated polyphenol toward thermal stress. This simple and cheap process is promising for applications in the food industry, because of the compatibility of the encapsulant with food products. 

The impact of high temperature (30°C-45°C) on ethanol fermentation by inunobilized K. marx-ianus was evaluated by Du Le et al. and Eiadpum et al. The immobilized yeast demonstrated faster sugar assimilation and higher ethanol level in the fermentation broth in comparison with the free yeast. The altered response of the free and immobilized yeast to thermal stress was attributed to the observed changes in the cell manbrane fatty acid composition. 

HDF has been identified as reaction product of a thermal treatment of sugars, especially the 6-desoxy sugar rhamnose [90], Analysis of the free sugars in the LMW-fraction revealed fructose-1,6-biphosphate (FBP) as the predominating carbohydrate in the LMW fraction (5.75 g/kg yeast), but no rhamnose was present [88]. To elucidate the contribution of FBP as precursors of HDF in the yeast fraction, the sugar phosphate was thermally degraded under the same conditions as used for the LMW fraction of yeast. The results revealed FBP, as effective precursor of HDF in aqueous model systems at lower reaction temperatures (100°C Table 19). It should be stressed that additions of the amino acids proline or alanine did not increase the concentrations of HDF from the carbohydrates listed in Table 19 (unpublished results). The data implied that FBP which was the predominant carbohydrate in yeast, is the... 

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