Methods and compositions for the recombinant biosynthesis of n-alkanes
The present disclosure identifies methods and compositions for modifying photoautotrophic organisms as hosts, such that the organisms efficiently convert carbon dioxide and light into n-alkanes, and in particular the use of such organisms for the commercial production of n-alkanes and related molecules.
1. An engineered cyanobacterium, wherein said engineered cyanobacterium comprises a recombinant acyl-ACP reductase enzyme and a recombinant alkanal decarboxylative monooxygenase enzyme, wherein at least one of said recombinant enzymes is heterologous with respect to said engineered cyanobacterium; and wherein said cyanobacterium, when cultured in the presence of light and carbon dioxide, produces n-alkanes, wherein the predominant n-alkane is n-pentadecane.
2. The engineered cyanobacterium of claim 1 , wherein said acyl-ACP reductase and alkanal decarboxylative monooxygenase enzymes are encoded by genes which are at least 95% identical to SEQ ID NO: 10 and SEQ ID NO: 12, respectively.
3. The engineered cyanobacterium of claim 1 , wherein said acyl-ACP reductase and alkanal decarboxylative monooxygenase enzymes are encoded by genes which are at least 95% identical to SEQ ID NO: 27 and SEQ ID NO: 29, respectively.
4. The engineered cyanobacterium of claim 1 , wherein said engineered cyanobacterium is a thermophile.
5. The engineered cyanobacterium of claim 1 , wherein the amount of said n-alkanes produced by said engineered cyanobacterium, when cultured in the presence of light and carbon dioxide, is at least two times the amount produced by an otherwise identical cyanobacterium, cultured under identical conditions, but lacking said recombinant acyl-ACP reductase and alkanal decarboxylative monooxygenase enzymes.
6. The engineered cyanobacterium of claim 1 , wherein said engineered cyanobacterium, when cultured in the presence of light and carbon dioxide, produces n-alkanes comprising both n-pentadecane and n-heptadecane, and wherein the percentage by mass of n-pentadecane relative to n-pentadecane plus n-heptadecane is at least 50%.
7. The engineered cyanobacterium of claim 1 , wherein said enzymes are encoded by recombinant genes incorporated into the genome of said engineered cyanobacterium.
8. The engineered cyanobacterium of claim 7 , wherein said acyl-ACP reductase and alkanal decarboxylative monooxygenase enzymes are at least 95% identical to SEQ ID NO:10 and SEQ ID NO:12, respectively.
9. The engineered cyanobacterium of claim 8 , wherein expression of said acyl-ACP reductase and alkanal decarboxylative monooxygenase enzymes is controlled by an inducible promoter.
10. The engineered cyanobacterium of claim 9 , wherein said engineered cyanobacterium further comprises a second operon encoding acyl-ACP reductase and alkanal decarboxylative monooxygenase enzymes which are at least 95% identical to SEQ ID NO: 27 and SEQ ID NO: 29, respectively.
11. The engineered cyanobacterium of claim 1 , wherein said enzymes are encoded by genes which are present in multiple copies in said engineered cyanobacterium.
12. The engineered cyanobacterium of claim 11 , wherein said enzymes are encoded by a plasmid.
13. The engineered cyanobacterium of claim 1 , wherein said acyl-ACP reductase enzyme and said alkanal decarboxylative monooxygenase enzyme are encoded by genes which are part of an operon, and wherein the expression of said genes is controlled by one or more inducible promoters.
14. The engineered cyanobacterium of claim 13 , wherein at least one promoter is a urea-repressible, nitrate-inducible promoter.
15. The engineered cyanobacterium of claim 14 , wherein said urea-repressible, nitrate-inducible promoter is P(nir07).
16. The engineered cyanobacterium of claim 1 , wherein said engineered cyanobacterium comprises at least two operons encoding distinct alkanal decarboxylative monooxygenase and acyl-ACP reductase enzymes.
17. The engineered cyanobacterium of claim 16 , wherein at least one operon encodes acyl-ACP reductase and alkanal decarboxylative monooxygenase enzymes which are at least 95% identical to SEQ ID NO: 10 and SEQ ID NO: 12, respectively.
18. The engineered cyanobacterium of claim 16 , wherein at least one operon encodes acyl-ACP reductase and alkanal decarboxylative monooxygenase enzymes which are at least 95% identical to SEQ ID NO: 27 and SEQ ID NO: 29, respectively.