Renewable chemicals and fuels from oleaginous yeast

Abstract

The invention provides methods of cultivating oil-bearing microbes using xylose alone or in combination with other depolymerized cellulosic material. Also provided are microorganisms comprising an exogenous gene encoding a polysaccharide degrading enzyme, such as a cellulase, a hemicellulase, a pectinase, or a driselase. Some methods of microbial fermentation are provided that comprise the use of xylose and depolymerized cellulosic materials for the production of oil-bearing microorgansims.

1 . A method of producing a fuel or a chemical, the method comprising the steps of:
 (a) heterotrophically culturing an oleaginous yeast in the presence of a fixed carbon source, wherein:
 (i) the fixed carbon source is selected from glycerol, depolymerized cellulosic material, sucrose, molasses, glucose, arabinose, galactose, xylose, fructose, mannose, or acetate; and 
 (ii) the oleaginous yeast accumulates at least 10% of its dry cell weight as triacylglyceride; 
   (b) isolating the triacylglyceride from the oleaginous yeast; and   (c) subjecting the isolated triacylglyceride to a chemical reaction to produce the fuel or chemical.   
     
     
         2 . The method of  claim 1 , wherein the depolymerized cellulosic material is selected from the group consisting of sugar cane bagasse, sugar beet pulp, corn stover, wood chips, sawdust, switchgrass, rice hull, corn fiber, wheat straw, rice straw, and citrus pulp. 
     
     
         3 . The method of  claim 1 , wherein the oleaginous yeast is selected from the group consisting of  Cryptococcus curvatus, Cryptococcus terricolus, Candida  sp.,  Lipomyces starkeyi, Lipomyces lipofer, Endomycopsis vernalis, Rhodotorula glutinis, Rhodotorula gracilis , and  Yarrowia lipolytica.    
     
     
         4 . The method of  claim 1 , wherein the oleaginous yeast contains at least one exogenous gene encoding a lipid pathway enzyme. 
     
     
         5 . The method of  claim 4 , wherein the lipid pathway enzyme is selected from the group consisting of a stearoyl-ACP desaturase, a glycerolipid desaturase, a pyruvate dehydrogenase, an acetyl-CoA carboxylase, an acyl carrier protein, a fatty acyl-ACP thioesterase, and a glycerol-3 phosphate acyltransferase. 
     
     
         6 . The method of  claim 1 , wherein said fuel or chemical is selected from the group consisting of renewable diesel, fatty acid esters, and jet fuel. 
     
     
         7 . The method of  claim 6 , wherein said renewable diesel conforms to the specifications of the ASTM D975 standard. 
     
     
         8 . The method of  claim 6 , wherein said biodiesel conforms to the specifications of the ASTM D6751 standard. 
     
     
         9 . The method of  claim 6 , wherein said jet fuel conforms to the specifications of the ASTM D1655 standard. 
     
     
         10 . The method of  claim 1 , wherein the triacylglyceride is isolated by lysing the oleaginous yeast. 
     
     
         11 . The method of  claim 10 , wherein the oleaginous yeast is lysed by mechanical means. 
     
     
         12 . The method of  claim 1 , wherein the chemical reaction is selected from the group consisting of cracking, (hydro)deoxygenation, esterification, and isomerization. 
     
     
         13 . The method of  claim 1 , further comprising distilling the fuel or chemical. 
     
     
         14 . A method for producing a triacylglyceride, said method comprising the steps of culturing an oleaginous yeast in a culture media to provide an oleaginous yeast comprising at least about 10% triacylglyceride by dry weight; and extracting the triacylglyceride from the oleaginous yeast. 
     
     
         15 . The method of  claim 14 , wherein said oleaginous yeast is selected from the group consisting of  Cryptococcus curvatus, Cryptococcus terricolus, Candida  sp.,  Lipomyces starkeyi, Lipomyces lipofer, Endomycopsis vernalis, Rhodotorula glutinis, Rhodotorula gracilis, Saccharomyces cerevisiae  and  Yarrowia lipolytica.    
     
     
         16 . The method of  claim 14 , wherein the oleaginous yeast is cultured in media comprising a carbon source selected from the group consisting of glucose, fructose, sucrose, lactose, galactose, xylose, mannose, rhamnose, arabinose, glycerol, and acetate. 
     
     
         17 . The method of  claim 14 , wherein the oleaginous yeast is cultured in media comprising a carbon source selected from the group consisting of depolymerized sugar beet pulp, black liquor, corn starch, depolymerized cellulosic material, corn stover, sugar beet pulp, sugar cane juice, switchgrass, milk whey, molasses, potato, rice, sorghum, and wheat. 
     
     
         18 . The method of  claim 14 , wherein said triacylglyceride is extracted by solvent extraction. 
     
     
         19 . A fuel or chemical produced by the method of  claim 1 .