Fermentive Production of Four Carbon Alcohols

Abstract

Methods for the fermentative production of four carbon alcohols is provided. Specifically, butanol, preferably isobutanol is produced by the fermentative growth of a recombinant bacterium expressing an isobutanol biosynthetic pathway.

1 - 82 . (canceled) 
     
     
         83 . A method of converting a renewable feedstock to a feedstock chemical comprising:
 a) providing a recombinant yeast host cell that expresses an engineered biosynthetic isobutanol pathway, wherein the engineered biosynthetic isobutanol pathway comprises an acetolactate synthase (ALS) enzyme, a ketol-acid reductoisomerase (KARI) enzyme, a dihydroxy-acid dehydratase (DHAD) enzyme, a branched chain keto acid decarboxylase enzyme (DC), and an alcohol dehydrogenase (ADH) enzyme, each of which is encoded by a heterologous gene that lacks a mitochondrial targeting sequence; and   b) growing the yeast host cells in fermentation medium comprising a renewable feedstock, whereby isobutanol is bioproduced from the renewable feedstock and is capable of being used as a chemical feedstock;   
       wherein the yeast host cells produce at least 6-fold more isobutanol when grown on sucrose under aerobic conditions compared to a recombinant yeast host cell lacking the engineered biosynthetic isobutanol pathway. 
     
     
         84 . The method of  claim 83 , further comprising recovering the bioproduced isobutanol. 
     
     
         85 . The method of  claim 84 , further comprising removing solids from the fermentation medium. 
     
     
         86 . The method of  claim 84 , wherein the recovering is by distillation, liquid-liquid extraction, adsorption, decantation, pervaporation, or combinations thereof. 
     
     
         87 . The method of  claim 85 , wherein the removing is by centrifugation, filtration, or decantation. 
     
     
         88 . The method of  claim 85 , wherein the removing occurs before the recovering.