Methods for the economical production of biofuel precursor that is also a biofuel from biomass

Abstract

Methods for producing a biofuel precursor are provided. Also provided are biocatalysts that convert a feedstock to a biofuel precursor.

What is claimed is: 
     
         1 . An animal feed product comprised of distillers dried grains derived from a fermentation process for the production of isobutanol, wherein said distillers dried grains comprise a spent yeast biocatalyst, said spent yeast biocatalyst engineered to express an isobutanol producing metabolic pathway comprising at least one exogenous gene. 
     
     
         2 . The animal feed product of  claim 1 , wherein said yeast biocatalyst does not contain DNA markers. 
     
     
         3 . The animal feed product of  claim 1 , wherein said yeast biocatalyst includes DNA consisting of natural DNA. 
     
     
         4 . The animal feed product of  claim 1 , wherein said isobutanol producing metabolic pathway comprises the following substrate to product conversions:
 (a) pyruvate to acetolactate;   (b) acetolactate to 2,3-dihydroxyisovalerate;   (c) 2,3-dihydroxyisovalerate to α-ketoisovalerate;   (d) α-ketoisovalerate to isobutyraldehyde; and   (e) isobutyraldehyde to isobutanol.   
     
     
         5 . The animal feed product of  claim 1 , wherein said yeast biocatalyst expresses an exogenously encoded acetolactate synthase. 
     
     
         6 . The animal feed product of  claim 1 , wherein said yeast biocatalyst expresses an exogenously encoded ketol-acid reductoisomerase. 
     
     
         7 . The animal feed product of  claim 1 , wherein said yeast biocatalyst expresses an exogenously encoded dihydroxy acid dehydratase. 
     
     
         8 . The animal feed product of  claim 1 , wherein said yeast biocatalyst expresses an exogenously encoded keto-isovalerate decarboxylase. 
     
     
         9 . The animal feed product of  claim 1 , wherein said yeast biocatalyst expresses an exogenously encoded isobutyraldehyde dehydrogenase. 
     
     
         10 . The animal feed product of  claim 1 , wherein said yeast biocatalyst is derived from  Saccharomyces cerevisiae.    
     
     
         11 . The animal feed product of  claim 1 , wherein said distillers dried grains comprise at least one additional product selected from the group consisting of unconsumed feedstock solids, nutrients, proteins, fibers, and oils. 
     
     
         12 . A method for producing distillers dried grains derived from a fermentation process for the production of isobutanol, said method comprising:
 (a) cultivating a yeast biocatalyst in a fermentation medium comprising at least one carbon source, wherein said yeast biocatalyst is engineered to express an isobutanol producing metabolic pathway comprising at least one exogenous gene;   (b) harvesting insoluble material derived from the fermentation process, said insoluble material comprising said yeast biocatalyst; and   (c) drying said insoluble material comprising said yeast biocatalyst to produce the distillers dried grains.   
     
     
         13 . The method of  claim 12 , wherein said yeast biocatalyst does not contain DNA markers. 
     
     
         14 . The method of  claim 12 , wherein said yeast biocatalyst includes DNA consisting of natural DNA. 
     
     
         15 . The method of  claim 12 , wherein said method further comprises step (d) of adding soluble residual material from the fermentation process to said distillers dried grains to produce distillers dried grains and solubles. 
     
     
         16 . The method of  claim 12 , wherein said distillers dried grains comprise at least one additional product selected from the group consisting of unconsumed feedstock solids, nutrients, proteins, fibers, and oils. 
     
     
         17 . The method of  claim 12 , wherein said isobutanol producing metabolic pathway comprises the following substrate to product conversions:
 (a) pyruvate to acetolactate;   (b) acetolactate to 2,3-dihydroxyisovalerate;   (c) 2,3-dihydroxyisovalerate to α-ketoisovalerate;   (d) α-ketoisovalerate to isobutyraldehyde; and   (e) isobutyraldehyde to isobutanol.   
     
     
         18 . The method of  claim 12 , wherein said yeast biocatalyst is derived from  Saccharomyces cerevisiae.