Fig. 5.

Supplementation of ethanol increases isobutanol production in S. cerevisiae. Fermentation experiments were performed aerobically at 30 °C in shake flasks in selective SCD medium without valine containing 40 g/L glucose. Pre-cultures carrying the episomal 2µ-plasmid IsoV100 were grown aerobically in fermentation medium, harvested at an OD₆₀₀ ≤ 3 and inoculated in fresh fermentation medium at a final OD₆₀₀ of 8. Fermentations were performed in duplicate per experiment and repeated at least twice. Error bars indicate standard deviation for experiments performed twice and standard error for experiments performed at least three times, respectively. a Isobutanol titer after successively blocking of competing pathways by deletion of key enzymes of biosynthesis pathways and supplementation of 1% (v/v) ethanol to fermentation medium: JWY0 (∆ilv2); JWY04 (∆ilv2; Δbdh1; Δbdh2; Δleu4; Δleu9; Δecm31; Δilv1); JWY13 (∆ilv2; Δbdh1; Δbdh2; Δleu4; Δleu9; Δecm31; Δilv1; Δpdc1; Δpdc5; Δmth1 (+ 169; + 393). b Isobutanol yield after 24 h