DEVELOPMENT OF SOME TOLERANT YEAST (SACCHAROMYCES CEREVISIAE) STRAINS TO HEAT AND SALT STRESSES

Abstract

All living organisms are subjected to changing in conservational conditions, to which they must adapt to. Stress is defined as a threat refers to the physiological balance of systems critical to survival organisms. Five yeast strains (Saccharomyces cerevisiae) were subjected to different adverse environmental situations, such as thermal, osmotic and oxidative (salt) stresses. The objective of this work was to detect the most tolerant yeast strains under salt or heat stresses. Five yeast strains were exposed in a first experiment to heat stress at 20°C or 40°C beside to the control at 30°C to detect the more tolerant strain. The same yeast strains were subjected in a second experiment to two different concentrations of salt stress (NaCl); 0.5 or 1.0 M, separately, for two days (at 30°C as normal temperature for growth), other strains were exposed to 0.5 M concentration of NaCl for 24 hours, then 1 M for another 24 hours. For the heat stress results, strain S4 was more tolerant at 40oCwith insignificant difference compared to the control (30oC), while it showed significant difference at 20°C. Strain S5 also was more tolerant at 20oC with insignificant difference compared to the control. For salt treatment, the only insignificant value was for strain S3at 0.5M NaCl compared with the control.