YEAST ORGANISM PRODUCING ISOBUTANOL AT A HIGH YIELD
There is disclosed a method of producing isobutanol. In an embodiment, the method includes providing a microorganism transformed with an isobutanol producing pathway containing at least one exogenous gene. The microorganism is selected to produce isobutanol from a carbon source at a yield of at least 10 percent theoretical. The method includes cultivating the microorganism in a culture medium containing a feedstock providing the carbon source, until isobutanol is produced. The method includes recovering the isobutanol. In one embodiment, the microorganism is a yeast with a Crabtree-negative phenotype. In another embodiment, the microorganism is a yeast microorganism with a Crabtree-positive phenotype. There is disclosed a microorganism for producing isobutanol. In an embodiment, the microorganism includes an isobutanol producing pathway containing at least one exogenous gene, and is selected to produce a recoverable quantity of isobutanol from a carbon source at a yield of at least 10 percent theoretical.
1 - 130 . (canceled)
131 . A method for producing isobutanol comprising:
a. providing a fermentation media comprising a carbon substrate; and
b. contacting said media with a recombinant yeast microorganism expressing an engineered isobutanol biosynthetic pathway wherein said pathway comprises the following substrate to product conversions:
i. pyruvate to acetolactate (pathway step a);
ii. acetolactate to 2,3-dihydroxyisovalerate (pathway step b);
iii. 2,3-dihydroxyisovalerate to α-ketoisovalerate (pathway step c);
iv. α-ketoisovalerate to isobutyraldehyde (pathway step d); and
v. isobutyraldehyde to isobutanol (pathway step e);
wherein
a) the substrate to product conversion of step (i) is performed by an acetolactate synthase enzyme;
b) the substrate to product conversion of step (ii) is performed by a ketal-acid reductoisomerase enzyme;
c) the substrate to product conversion of step (iii) is performed by a dihydroxy acid dehydratase enzyme;
d) the substrate to product conversion of step (iv) is performed by a decarboxylase enzyme; and
e) the substrate to product conversion of step (v) is performed by an alcohol dehydrogenase enzyme;
and wherein the recombinant yeast microorganism comprises one or more inactivated endogenous pyruvate decarboxylase genes;
whereby isobutanol is produced.