2.4.2 Microorganism and culture media
The industrial yeast strain S. cerevisiae (obtained from Bidestan Alcohol Production Company, Iran) was used in this study. This strain is commonly used in the production of alcohol and can be used as active dry yeast. The cultures were maintained on YPD agar plates containing Dextrose (2%, w/v), peptone water (1%, w/v), yeast extract (0.5%, w/v), and agar (2%, w/v). The seed culture also was prepared by the YPD medium containing (20 g L-1 dextrose, 10 g L-1 yeast extract, 20 g L-1 peptone water) at 30°C and 180 rpm. The minimal medium including Dextrose, 20 g/l; KH2PO4, 13g/l; K2HPO4, 2.7g/l; (NH4)2SO4, 5g/l; K2SO4, 2g/l; (MgSO4).7H2O, 2.5g/l; NaCl, 0.1g/l; CaCl2.2H2O, 0.35g/l; H2SO4, 1 ml; 4.5 ml of trace elements solution including FeSO4.7H2O, 2g/l; MnSO4.H2O, 0.3g/l; CoCl2.6H2O, 0.05g/l; H3BO3, 0.002g/l; CuSO4.5H2O, 0.6g/l; ZnCl2, 1g/l; KI, 0.008g/l; MoNa2O4.2H2O, 0.002g/l; Biotin, 0.04g/l was used for the cultivation. 47 ml of minimal medium was inoculated with 3 ml of seed culture at the mid-exponential phase at 30°C, 150 rpm, and the initial measured pH of the medium was adjusted to 5. The chosen compounds were added to the minimal medium in compliance with the Brenda database concentrations. Concentrated solutions of these compounds have been separately sterilized by autoclaving them at 121°C for 15 min.