Patent ID: 8431374

Claim:
A method of making isobutanol, the method comprising: a) providing a feedstock comprising a sugar selected from the group consisting of: i) a six-carbon sugar; ii) a six-carbon sugar oligomer; iii) a five-carbon sugar; and iv) any combination of i) through iii); b) contacting the feedstock of a) with an engineered microorganism under suitable fermentation conditions such that said engineered microorganism converts the feedstock into isobutanol at: i) a yield of at least 68 percent theoretical yield; ii) a productivity of at least 0.75 grams isobutanol per liter per hour; and iii) a total titer of at least 1.6% (w/v) of isobutanol in water, wherein said engineered microorganism expresses exogenous genes encoding an acetolactate synthase that catalyzes the conversion of pyruvate to acetolactate, a ketol-acid reductoisomerase that catalyzes the conversion of acetolactate to 2,3-dihydroxyisovalerate, a dihydroxy acid dehydratase that catalyzes the conversion of 2,3-dihydroxyisovalerate to α-ketoisovalerate, a ketoisovalerate decarboxylase that catalyzes the conversion of α-ketoisovalerate to isobutyraldehyde, and an isobutyraldehyde dehydrogenase that catalyzes the conversion of isobutyraldehyde to isobutanol; and c) recovering the isobutanol.