Assessment of stress resistance of industrial strains of Saccharomyces cerevisiae for designing selection media

The two main methods for obtaining microbial strains with specific characteristics for application in the industry are isolation from natural sources and using random mutagenesis. Characterization of all isolated strains is very time-consuming and expensive. In this study the tolerance of some strains of Saccharomyces cerevisiae to different stresses was measured and the association between these stresses and tolerance to osmotic pressure and production of intracellular trehalose determined, aiming at applying the results to designing selection media. The viability (percent cell survival) of different strains of Saccharomyces cerevisiae was assessed by exposure to a 3M Nacl solution, a 40% sorbitol solution, a freezing shock at -20º C, and a heat shock at 52º C. In addition, the intracellular accumulation of trehalose was determined by the antrone reagent. The associations between these factors and resistance of Saccharomyces cerevisiae strains were then determined using statistical tests. Strong correlations were observed between resistance to NaCl- and sorbitol-introduced stress and strains of Saccharomyces cerevisiae (p<0.01). There was also a strong association between intracellular trehalose accumulation and resistance to heat shock (p<0.01). While sugars can not select osmotolerant cells, Nacl is a very strong selector for more specific isolation of more resistant cells in a suspension. Similarly, heat shock stress is very efficient in selecting cells with a higher intracellular trehalose accumulation in a suspension.