Yeast cells were grown in defined medium containing (per liter deionised water): 100 g D-glucose, 1 g K2HPO4, 1 g K2H2PO4, 0.2 g ZnSO4, 0.2 g MgSO4, 2 g yeast extract and 2 g NH4SO4. All the media components were purchased from Sigma Chemical Company. Medium contained NaCl (commercial NaCl was used) 6% w/v for 24 hours were used for pre conditioning under osmotic stress experiments. The total volume of the medium for each fermentation medium was 250 ml.