PDR18 over-expression leads to higher ethanol production yield in a high gravity-like fermentation medium. Comparison of the PDR18 transcript levels (B), and the extracellular concentrations of ethanol (C) and glucose (D), accumulated/used during cultivation in fermentation medium, containing 30 % glucose, of S. cerevisiae yeast strains BY4741 (◊), BY4741_Δpdr18 (▵) and BY4741_ + PDR18 (□). A: Growth curves, followed by measuring culture OD600nm, are representative of at least three independent experiments. B: The relative values of PDR18 mRNA/ACT1 mRNA, as obtained through RT-PCR, are the means of at least three independent experiments, error bars indicating standard deviation. The PDR18 mRNA relative value for the parental BY4741 in control conditions was set as 1 and the remaining values were calculated relative to it. C and D: Ethanol and glucose concentration levels, assessed using HPLC, are also mean values of at least three independent experiments, error bars indicating standard deviation.