Patent ID: 8017375

Claim:
A recombinant yeast microorganism for producing isobutanol, the recombinant yeast microorganism comprising an isobutanol producing metabolic pathway, wherein said isobutanol producing metabolic pathway comprises the following substrate to product conversions: (i) pyruvate to acetolactate; (ii) acetolactate to 2,3-dihydroxyisovalerate; (iii) 2,3-dihydroxyisovalerate to α-ketoisovalerate; (iv) α-ketoisovalerate to isobutyraldehyde; and (v) isobutyraldehyde to isobutanol; wherein said recombinant yeast microorganism expresses: (a) an acetolactate synthase to catalyze the conversion of pyruvate to acetolactate; (b) a ketol-acid reductoisomerase to catalyze the conversion of acetolactate to 2,3-dihydroxyisovalerate; (c) a dihydroxy acid dehydratase to catalyze the conversion of 2,3-dihydroxyisovalerate to α-ketoisovalerate; (d) an α-ketoisovalerate decarboxylase from Lactococcus lactis to catalyze the conversion of α-ketoisovalerate to isobutyraldehyde; and (e) an alcohol dehydrogenase to catalyze the conversion of isobutyraldehyde to isobutanol; wherein the recombinant yeast microorganism has been engineered to disrupt, mutate, or delete one or more endogenous pyruvate decarboxylase (PDC) genes, wherein said recombinant yeast microorganism has reduced endogenous PDC activity as compared to the corresponding yeast microorganism that has not been engineered to have reduce endogenous PDC activity, and wherein said recombinant yeast microorganism produces: (A) isobutanol at a yield which is at least 10% of the theoretical yield of isobutanol from glucose; and/or (B) ethanol at a yield which is 1.8% or less of the theoretical yield of ethanol from glucose.