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.