Fatty acid-producing hosts
Described are hosts for overproducing a fatty acid product such as a fatty acid. The hosts include an exogenous nucleic acid encoding a thioesterase and, optionally, an exogenous nucleic acid encoding an acetyl-CoA carboxylase, wherein an acyl-CoA synthetase in the hosts are functionally deleted. The hosts preferably include the nucleic acid encoding the thioesterase at an intermediate copy number. The hosts are preferably recombinantly stable and growth-competent at 37° C. Methods of producing a fatty acid product comprising culturing such hosts at 37° C. are also described.
1. An isolated host cell for producing a fatty acid product comprising an exogenous nucleic acid encoding a thioesterase (EC 3.1.2.14), wherein:
the thioesterase comprises a sequence at least 80% identical to SEQ ID NO:2;
the host includes no more than 250 copies of the nucleic acid;
an acyl-CoA synthetase (EC 6.2.1.3) in the host is functionally deleted; and
the host is recombinantly stable at 37° C.
2. The host of claim 1 wherein the host is growth-competent at 37° C.
3. The host of claim 1 wherein the nucleic acid is operably connected to an origin of replication obtained from a plasmid selected from the group consisting of pBR322, pACYC, pBBR1, and pSC101.
4. The host of claim 1 wherein the host includes no more than 30 copies of the nucleic acid.
5. The host of claim 1 wherein the host includes of from 2 to 250 copies of the nucleic acid.
6. The host of claim 1 wherein the host includes of from 5 to 100 copies of the nucleic acid.
7. The host of claim 1 wherein the host includes of from 5 to 30 copies of the nucleic acid.
8. The host of claim 1 wherein the exogenous nucleic acid is codon optimized.
9. The host of claim 1 wherein the exogenous nucleic acid is a nucleic acid sequence comprising SEQ ID NO:1.
10. The host of claim 1 wherein the thioesterase is obtained from Umbellularia californica.
11. The host of claim 1 further comprising an exogenous nucleic acid encoding an acetyl-CoA carboxylase (EC 6.4.1.2).
12. The host of claim 11 wherein the nucleic acid encoding the acetyl-CoA carboxylase includes an artificial operon comprising accA, accB, accC, and accD from E. coli.
13. A method for producing a fatty acid product comprising culturing an isolated host as recited in claim 1 at 37° C., wherein the host overproduces the fatty acid product.
14. The method of claim 13 further comprising maintaining the nucleic acid in the host at a copy number of 30 copies or fewer.
15. The method of claim 13 comprising maintaining the nucleic acid in the host at a copy number of from 10 to 30.
16. The method of claim 13 wherein the nucleic acid is operably connected to an inducible promoter, and wherein the method further comprises culturing the host in presence of a sub-saturating amount of an effector of the inducible promoter.
17. The method of claim 13 wherein the nucleic acid is operably connected to a repressible promoter, and wherein the method further comprises culturing the host in presence of a repressor of the repressible promoter.
18. The method of claim 13 further comprising:
maintaining the nucleic acid in the host at a copy number of 50 copies or more; and
culturing the host in presence of a sub-saturating amount of an effector of an inducible promoter operably connected to the nucleic acid, or
culturing the host in presence of a repressor of a repressible promoter operably connected to the nucleic acid.
19. The method of claim 13 wherein the cultured host further comprises an exogenous nucleic acid encoding an acetyl-CoA carboxylase (EC 6.4.1.2).
20. The host of claim 1 wherein the host is a microorganism, and the thioesterase is a thioesterase comprising a sequence at least 80% identical to SEQ ID NO:2.
21. The host of claim 1 wherein the host is a microorganism, the thioesterase is a thioesterase comprising a sequence at least 80% identical to SEQ ID NO:2, and the acyl-CoA synthetase is a microbial acyl-CoA synthetase.
22. The host of claim 21 wherein the host is a bacterium or a yeast.
23. The host of claim 22 wherein the thioesterase is a thioesterase comprising a sequence at least 90% identical to SEQ ID NO:2.
24. The host of claim 1 wherein the host is an isolated host cell, the host is a bacterium or a yeast, the thioesterase is a thioesterase comprising a sequence at least 80% identical to SEQ ID NO:2, and the acyl-CoA synthetase is a FadD acyl-CoA synthetase or an FAA acyl-CoA synthetase.
25. The host of claim 1 wherein the host is an isolated host cell, the host is a bacterium or a yeast, the thioesterase is a thioesterase comprising a sequence at least 90% identical to SEQ ID NO:2, and the acyl-CoA synthetase is a FadD acyl-CoA synthetase or an FAA acyl-CoA synthetase.