Yeast organism producing isobutanol at a high yield

Abstract

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.