Patent ID: 8614085

Claim:
A recombinant yeast cell comprising: a) an isobutanol biosynthetic pathway, wherein the recombinant yeast cell comprises heterologous genes encoding an acetolactate synthase, an acetohydroxy acid isomeroreductase, an acetohydroxy acid dehydratase, a branched-chain keto acid decarboxylase, and a branched-chain alcohol dehydrogenase that perform the following substrate to product conversions: i) pyruvate to acetolactate catalyzed by the acetolactate synthase, ii) acetolactate to 2,3-dihydroxyisovalerate catalyzed by the acetohydroxy acid isomeroreductase, iii) 2,3-dihydroxyisovalerate to α-ketoisovalerate catalyzed by the acetohydroxy acid dehydratase, iv) α-ketoisovalerate to isobutyraldehyde catalyzed by the branched-chain keto acid decarboxylase, v) isobutyraldehyde to isobutanol catalyzed by the branched-chain alcohol dehydrogenase; and b) at least one genetic modification in an endogenous gene encoding a multidrug ATP-binding cassette transporter protein, wherein the multidrug ATP-binding cassette transporter protein has at least 95% sequence identity to SEQ ID NO:50, 52, 54, 56, or 58, wherein the at least one genetic modification decreases activity of the endogenous multidrug resistance ATP-binding cassette transporter protein, and; wherein the yeast cell has improved tolerance to isobutanol as compared to the corresponding yeast cell that lacks the at least one genetic modification of (b).