Production of branched-chain alcohols by photosynthetic microorganisms

1. A recombinant photosynthetic microorganism comprising at least one heterologous nucleic acid sequence that encodes a branched-chain 2-ketoacid decarboxylase and at least one heterologous nucleic acid sequence that encodes an enzyme selected from the group consisting of a citramalate synthase, a 2-methylmalate dehydratase, a 3-isopropylmalate dehydratase, and a 3-isopropylmalate dehydrogenase, wherein the recombinant photosynthetic microorganism produces 2-methyl-1-butanol.

2. The recombinant photosynthetic microorganism of claim 1 , wherein the branched-chain 2-ketoacid decarboxylase is selected from the group consisting of a Saccharomyces cerevisae PDC1 gene product, a Pichia stipitis PDC1 gene product, a Saccharomyces cerevisae PDC5 gene product, a Saccharomyces cerevisae PDC6 gene product, a Saccharomyces cerevisae ARO10 gene product, a Saccharomyces cerevisae THI3 gene product, a Pichia stipitis PDC 3-6 Kivd gene product, a Pichia stipitis PDC2 gene product, a Mycobacterium tuberculosis KDC gene product, a Lactococcus lactis KDCa gene product, and a variant or homolog of any thereof.

3. The recombinant photosynthetic microorganism of claim 2 , wherein the heterologous nucleic acid sequence encodes Lactococcus lactis KDCa gene product or a variant thereof.

4. The recombinant photosynthetic microorganism of claim 3 , wherein the heterologous nucleic acid sequence encodes a Lactococcus lactis KDCa -S286Y, KDCa S286U, or F381W gene product, or a variant of any thereof.

5. The recombinant photosynthetic microorganism of claim 2 , wherein the heterologous nucleic acid sequence encodes a Pichia stipitis PDC3-6 gene product or a variant thereof.

6. The recombinant photosynthetic microorganism of claim 2 , further comprising a heterologous nucleic acid sequence encoding an alcohol dehydrogenase.

7. The recombinant photosynthetic microorganism of claim 6 , wherein alcohol dehydrogenase is a branched-chain alcohol dehydrogenase.

8. The recombinant photosynthetic microorganism of claim 7 , wherein the alcohol dehydrogenase is selected from the group consisting of a Saccharomyces cerevisae ADH1 gene product, a Saccharomyces cerevisae ADH2 gene product, a Saccharomyces cerevisae ADH3 gene product, a Saccharomyces cerevisae ADH6 gene product, a Saccharomyces cerevisae ADH7 gene product, a Saccharomyces cerevisae GRE2 gene product, a Saccharomyces cerevisae SFA1 gene product, a Saccharomyces cerevisae YPR1 gene product, a Pichia stipitis AdH3 gene product, a Pichia stipitis ADH6 gene product, a Pichia stipitis ADH7 gene product, a GRE2 gene product, a Mycobacterium tuberculosis ADH1 gene product, a Mycobacterium tuberculosis ADH gene product, a Mycobacterium tuberculosis ADHb gene product, an E. coli yqhD gene product, an Equus caballus ADHE gene product, and a variant or homolog of any thereof.

9. The recombinant photosynthetic microorganism of claim 8 , wherein the heterologous nucleic acid sequence encodes a Saccharomyces cerevisae ADH6 gene product.

10. A recombinant photosynthetic microorganism according to claim 1 , wherein the photosynthetic microorganism comprises at least one heterologous nucleic acid sequence that encodes a citramalate synthase.

11. A recombinant photosynthetic microorganism according to claim 1 , wherein the recombinant photosynthetic microorganism further comprises at least one heterologous nucleic acid sequence that encodes at least one enzyme selected from the group consisting of an acetolactate synthase, a ketol-acid reductoisomerase, and a dihydroxyacid dehydratase.

12. A recombinant photosynthetic microorganism according to claim 11 , wherein the recombinant photosynthetic microorganism comprises at least one heterologous nucleic acid sequence that encodes an acetolactate synthase.

13. A recombinant photosynthetic microorganism according to claim 1 , wherein the recombinant photosynthetic microorganism further comprises at least one heterologous nucleic acid sequence that encodes at least one enzyme selected from the group consisting of a homoserine dehydrogenase, a homoserine kinase, a threonine synthase, and a threonine ammonia-lyase.

14. A recombinant photosynthetic microorganism according to claim 13 , wherein the recombinant photosynthetic microorganism comprises at least one heterologous nucleic acid sequence that encodes a threonine ammonia-lyase.

15. The recombinant photosynthetic microorganism of claim 1 , wherein the photosynthetic microorganism is a eukaryotic microalga.

16. The recombinant photosynthetic microorganism of claim 15 , wherein the photosynthetic microorganism is selected from the group consisting of Achnanthes, Amphiprora, Amphora, Ankistrodesmus, Asteromonas, Bookelovia, Borodinella, Botryococcus, Bracteococcus, Chaetoceros, Carteria, Chlamydomonas, Chlorococcum, Chlorogonium, Chlorella, Chroomonas, Chrysosphaera, Cricosphaera, Crypthecodinium, Cryptomonas, Cyclotella, Dunaliella, Ellipsoidon, Emiliania, Eremosphaera, Ernodesmius, Euglena, Franceia, Fragilaria, Gloeothamnion, Haematococcus, Halocafeteria, Hymenomona, Isochrysis, Lepocinclis, Micractinium, Monoraphidium, Nannochloris, Nannochloropsis, Navicula, Neochloris, Nephrochloris, Nephroselmis, Nitzschia, Ochromonas, Oedogonium, Oocystis, Ostreococcus, Pavlova, Parachlorella, Pascheria, Phaeodactylum, Phagus, Platymonas, Pleurochrysis, Pleurococcus, Prototheca, Pseudochlorella, Pyramimonas, Pyrobotrys, Scenedesmus, Skeletonema, Spyrogyra, Stichococcus, Tetraselmis, Thalassiosira, Viridiella , and Volvox.

17. The recombinant photosynthetic microorganism of claim 1 , wherein the photosynthetic microorganism is a cyanobacterium.

18. The recombinant photosynthetic microorganism of claim 17 , wherein the photosynthetic microorganism is selected from the group consisting of Chamaesiphon, Chroococcus, Cyanobacterium, Cyanobium, Dactylococcopsis, Gloeobacter, Gloeocapsa, Gloeothece, Microcystis, Prochlorococcus, Prochloron, Synechococcus, Synechocystis,Chroococcidiopsis, Cyanocystis, Dermocarpella, Myxosarcina, Pleurocapsis, Stanieria, Xenococcus, Arthrospira, Borzia, Crinalium, Geitlerinema, Halospirulina, Leptolyngbya, Limnothrix, Lyngbya, Microcoleus, Oscillatoria, Planktothrix, Prochlorothrix, Pseudanabaena, Spirulina, Starria, Symploca, Trichodesmium , and Tychonema, Anabaena, Anabaenopsis, Aphanizomenon, Calothrix, Cyanospira, Cylindrospermopsis, Cylindrospermum, Nodularia, Nostoc, Chlorogloeopsis, Fischerella, Geitleria, Nostochopsis, Iyengariella, Stigonema, Rivularia, Scytonema , and Tol othri.

19. The recombinant photosynthetic microorganism of claim 18 , wherein the photosynthetic microorganism is Synechococcus or Synechocystis.

20. A method for producing 2-methyl-1-butanol, said method comprising:

(i) providing a culture medium comprising a carbon source,

(ii) culturing the recombinant photosynthetic microorganism of claim 1 in said culture medium under photoautotrophic conditions, and

(iii) recovering 2-methyl-1-butanol from said culture medium.

21. The method of claim 20 , wherein the culture medium provides inorganic carbon as substantially the sole carbon source.

22. The method of claim 21 , wherein the inorganic carbon in the culture medium is CO2.

23. The method of claim 20 , wherein the recombinant photosynthetic further comprises a heterologous nucleic acid sequence encoding an alcohol dehydrogenase.

24. The method of claim 20 , wherein the recombinant photosynthetic further comprises a heterologous nucleic acid sequence encoding encodes at least one enzyme selected from the group consisting of an acetolactate synthase, a ketol-acid reductoisomerase, and a dihydroxyacid dehydratase.

25. The method of claim 20 , wherein said at least one heterologous nucleic acid sequence further encodes one or more gene products selected from the group consisting of a homoserine dehydrogenase gene product, a homoserine kinase gene product, a threonine synthase gene product, and a threonine ammonia-lyase gene product.