Reduction of the toxic effect of impurities from raw materials by extractive fermentation

1. A method of producing a bioproduct from engineered microbial cells, comprising:

(a) providing an aqueous fermentation broth comprising a crude carbon source;

(b) inoculating said fermentation broth with microbial cells, engineered to enhance expression of one or more of a gene encoding an enzyme selected from the group consisting of thioesterase, acyl-CoA synthase, and ester synthase, and wherein a gene encoding an acyl-CoA dehydrogenase is attenuated or absent in the engineered microbial cells;

(c) incubating the inoculated fermentation broth;

(d) thereby producing and secreting a bioproduct; and

(e) treating said fermentation broth with a hydrophobic solvent wherein a toxic side product present in said crude carbon source is soluble in said hydrophobic solvent.

2. The method of claim 1 , further comprising:

pretreating said fermentation broth with an initial volume of a hydrophobic solvent; and

separating said fermentation broth from said hydrophobic solvent.

3. The method of claim 2 , wherein the pretreating step comprises:

mixing said initial volume of hydrophobic solvent with said fermentation broth at a ratio of at most about 1:1 (volume:volume) hydrophobic solvent:fermentation broth.

4. The method of claim 2 , wherein the pretreating step comprises:

mixing said initial volume of hydrophobic solvent with said fermentation broth at a ratio of from about 1:3 to about 1:100 (volume:volume) hydrophobic solvent:fermentation broth.

5. The method of claim 1 , wherein said toxic side product comprises at least one compound selected from the group consisting of furfural; 5-hydroxymethyl furfural; aliphatic acids; phenolic compounds; 4-hydroxybenzaldehyde; 4-hydroxybenzoic acid; hydroquinone; catechol; 4-methyl catechol; syringaldehyde; syringic acid; guaiacol; vanillic acid; vanillin; 1-acetyl-9H-pyrido[3,4B]indole; 1-acetylpyrrolidine; 2,3-dihydrobenzofuran; 2,5-dimethyl-4-hydroxy-3(2H)-furnine; 2,5-dimethylpyrazine; 2-hydroxy-3-methyl-2-cyclopenten-1-one; 5,6-dihydro-6-pentyl-2H-pyran-4-one; benzeneacetic acid; benzoic acid; furan carboxylic acid methylethylester; hexadecanoic acid; hexanoic acid; pentanoic acid; trimethylpyrazine; furan; n-hexanoic-acid; and 4-carboxybenzaldehyde.

6. The method of claim 1 , wherein said hydrophobic solvent comprises alkanes, esters, olefins, fatty acids, fatty alcohols, aldehydes, or ketones.

7. The method of claim 6 , wherein said hydrophobic solvent comprises hexadecane, eicosadecene, C1C12:0 ester, C1C12:1 ester, C1C14:0 ester, C1C14:1 ester, C1C16:0 ester, C1C16:1 ester, C1C18:1 ester, C2C12:0 ester, C2C12:1 ester, C2C14:0 ester, C2:C14:1 ester, C2C16:0 ester, C2C16:1 ester, C2:C18:1 ester, or biodiesel.

8. The method of claim 1 , wherein said bioproduct comprises one or more of alkanes, esters, olefins, fatty acids, fatty alcohols, aldehydes, or ketones.

9. The method of claim 8 , wherein said bioproduct comprises hexadecane, eicosadecene, C1C12:0 ester, C1C12:1 ester, C1C14:0 ester, C1C14:1 ester, C1C16:0 ester, C1C16:1 ester, C1C18:1 ester, C2C12:0 ester, C2C12:1 ester, C2C14:0 ester, C2:C14:1 ester, C2C16:0 ester, C2C16:1 ester, C2:C18:1 ester, or biodiesel.

10. The method of claim 1 , wherein said bioproduct is a biofuel.

11. The method of claim 1 , wherein said hydrophobic solvent and said bioproduct comprise similar molecules.

12. The method of claim 1 , wherein said crude carbon source is derived from biomass.

13. The method of claim 12 , wherein said crude carbon source comprises hydrolyzed cellulosic material, hydrolyzed hemicellulosic material, or molasses.

14. The method of claim 13 , wherein said cellulosic or hemicellulosic material comprises wood, grass, forestry waste, agricultural residue, or agroindustrial residue.

15. A method of producing a bioproduct from engineered microbial cells, comprising:

(a) providing an aqueous fermentation broth comprising a crude carbon source;

(b) inoculating said fermentation broth with engineered microbial cells wherein the engineered microbial cells are engineered to enhance expression of a gene encoding an enzyme selected from the group consisting of thioesterase, acyl-CoA synthase, and ester synthase and wherein a gene encoding an acyl-CoA dehydrogenase is attenuated or absent in the engineered microbial cell; and

(c) incubating the inoculated fermentation broth,

wherein the engineered microbial cells produce a bioproduct and said bioproduct is a hydrophobic solvent immiscible with said fermentation broth, wherein any toxic side product present in said crude carbon source is soluble in a hydrophobic solvent.

16. The method of claim 15 , wherein the gene encoding an acyl-CoA dehydrogenase is fadE.