Fig. 4

Evaluation of fermentation capacities at normal and three stress conditions. a Principal component analysis (PCA) of fermentation data from all the 36 Spt15 mutant strains and the wild-type strain BY4741 at normal and three stress conditions. b PCA of fermentation data of the strains at hyperosmotic stress. The strains were evaluated in four batches, indicated using the circle, triangle, square and diamond symbols, respectively. Compared to the wild-type strain in each batch, mutant Spt15 strains showing increased or decreased fermentation capacities are indicated by upward arrow or downward arrow, respectively. In a and b, fermentation data include cell growth (purple lines), glucose consumption (turquoise lines) and ethanol production (orange lines) during fermentation (hours 0, 6, 12, 18, 24, 30, 36, 42 and 48). Means of biological duplicates are used. c Comparison of fermentation performance of three most stress tolerant (A140G, P169G, R238K) and two most stress-sensitive (S118L, L214V) Spt15 mutant strains with the wild-type strain BY4741 at normal, hyperosmotic, thermal and ethanol stress conditions. Error bars represent standard deviation among biological duplicates. In the c lower right panel, ethanol level dropped not only during fermentation of the wild-type strain, but also during fermentations of the S118L and L214V strains, which might be because of ethanol evaporation and no cell growth