STRESS CO-TOLERANCE AND TREHALOSE CONTENT IN BAKING STRAINS OF SACCHAROMYCES-CEREVISIAE

Fourteen wild-type baking strains of Saccharomyces cerevisiae were gro wn in batch culture to true stationary phase (exogenous carbon source exhausted) and tested for their trehalose content and their tolerance to heat (52 degrees C for 4.5 min), ethanol (20% v/v for 30 min), H2O2 (0.3 M for 60 min), rapid freezing (-196 degrees C for 20 min, coolin g rate 200 degrees C min(-1)), slow freezing (-20 degrees C for 24 h, cooling rate 3 degrees C min(-1)), salt (growth in 1,5 M NaCl agar) or acetic acid (growth in 0.4% w/v acetic acid agar) stresses. Stress to lerance among the strains was highly variable and up to 1000-fold diff erences existed between strains for some types of stress, Compared wit h previously published reports, all strains were tolerant to H2O2 stre ss, Correlation analysis of stress tolerance results demonstrated rela tionships between tolerance to H2O2 and tolerance to all stresses exce pt ethanol, This may imply that oxidative processes are associated wit h a wide variety of cellular stresses and also indicate that the gener al robustness associated with industrial yeast may be a result of thei r oxidative stress tolerance, In addition, H2O2 tolerance might be a s uitable marker for the general assessment of stress tolerance in yeast strains, Trehalose content failed to correlate with tolerance to any stress except acetic acid, This may indicate that the contribution of trehalose to tolerance to other stresses is either small or inconsiste nt and that trehalose may not be used as a general predictor of stress tolerance in true stationary phase yeast.