Ethanol production in microorganisms
The present disclosure relates to methods and compositions for engineering photoautotrophic organisms to convert carbon dioxide and light into fatty acid esters and other molecules, including biofuels. The molecules are then secreted by the organism into a growth medium.
1. A method for production of ethanol, comprising: culturing an engineered cyanobacterium in a culture medium in the presence of light and inorganic carbon, wherein said engineered cyanobacterium comprising a recombinant pyruvate decarboxylase nucleic acid sequence encoding a pyruvate decarboxylase having EC 4.1.1.1 and a plurality of recombinant alcohol dehydrogenase nucleic acid sequences encoding an alcohol dehydrogenase having EC 1.1.1.1 or EC 1.1.1.2, wherein the expression level the alcohol dehydrogenase and the expression level of the pyruvate decarboxylase are regulated by separate promoters, wherein the expression level of alcohol dehydrogenase in the engineered cyanobacterium is greater than the expression level of alcohol dehydrogenase in a control engineered cyanobacterium comprising a recombinant alcohol dehydrogenase nucleic acid sequence and a recombinant pyruvate decarboxylase nucleic acid sequence regulated together by a single promoter, and wherein the engineered cyanobacterium produces ethanol in an amount greater than a non-engineered cyanobacterium , when cultured under identical conditions.
2. The method of claim 1 , wherein different promoters are used to achieve differential expression of each recombinant nucleic acid sequence.
3. The method of claim 2 , wherein one of said recombinant nucleic acid sequences is controlled by an inducible promoter and one of said recombinant nucleic acid sequences is modulated by a constitutive promoter.
4. The method of claim 3 , wherein the expression of said recombinant alcohol dehydrogenase nucleic acid sequence is modulated by a constitutive promoter.
5. The method of claim 3 , wherein the expression of said recombinant pyruvate decarboxylase nucleic acid sequence is modulated by a chemically-affected promoter.
6. The method of claim 5 , wherein the expression of said recombinant pyruvate decarboxylase nucleic acid sequence is modulated by an ammonia-repressible promoter.
7. The method of claim 6 , wherein said inducible promoter is nirA.
8. The method of claim 1 , wherein said recombinant alcohol dehydrogenase nucleic acid sequence and said recombinant pyruvate decarboxylase nucleic acid sequence are encoded by (1) the same plasmid, or (2) the same chromosome, or (3) separate plasmids, or (4) separately on a chromosome and a plasmid.
9. The method of claim 1 , wherein the activity of alcohol dehydrogenase is varied by controlling the level of a co-factor required by alcohol dehydrogenase.
10. The method of claim 1 , wherein said cyanobacterium is a thermophilic cyanobacterium.
11. The method of claim 1 , wherein said recombinant alcohol dehydrogenase gene encodes a Moorella alcohol dehydrogenase.
12. An engineered cyanobacterium comprising a recombinant pyruvate decarboxylase nucleic acid sequence encoding a pyruvate decarboxylase having EC 4.1.1.1 and a plurality of recombinant alcohol dehydrogenase nucleic acid sequences encoding an alcohol dehydrogenase having EC 1.1.1.1 or EC 1.1.1.2, wherein the expression level the alcohol dehydrogenase and the expression level of the pyruvate decarboxylase are regulated by separate promoters, wherein the expression level of alcohol dehydrogenase in the engineered cyanobacterium is greater than the expression level of alcohol dehydrogenase in a control engineered cyanobacterium comprising a recombinant alcohol dehydrogenase nucleic acid sequence and a recombinant pyruvate decarboxylase nucleic acid sequence regulated together by a single promoter, and wherein the engineered cyanobacterium produces ethanol in an amount greater than a non-engineered cyanobacterium , when cultured under identical conditions.
13. The engineered cyanobacterium of claim 12 , wherein the expression of alcohol dehydrogenase is driven by different promoters.
14. The engineered cyanobacterium of claim 12 , wherein said cyanobacterium lacks a functioning lactate dehydrogenase gene or lactate dehydrogenase enzyme activity.
15. The engineered cyanobacterium of claim 12 , wherein said cyanobacterium is a thermophile or a strain of Synechococcus.
16. The engineered cyanobacterium of claim 13 , wherein one of said recombinant nucleic acid sequences are controlled by an inducible promoter and one of said recombinant nucleic acid sequence is modulated by a constitutive promoter.
17. The engineered cyanobacterium of claim 16 , wherein the expression of said recombinant alcohol dehydrogenase nucleic acid sequence is modulated by a constitutive promoter.
18. The engineered cyanobacterium of claim 16 , wherein the expression of said recombinant pyruvate decarboxylase nucleic acid sequence is modulated by a chemically-affected promoter.
19. The engineered cyanobacterium of claim 18 , wherein the expression of said recombinant pyruvate decarboxylase nucleic acid sequence is modulated by an ammonia-repressible promoter.
20. The engineered cyanobacterium of claim 19 , wherein said inducible promoter is nirA.
21. The engineered cyanobacterium of claim 12 , wherein said recombinant alcohol dehydrogenase nucleic acid sequence and said recombinant pyruvate decarboxylase nucleic acid sequence are encoded by (1) the same plasmid, or (2) the same chromosome, or (3) separate plasmids, or (4) separately on a chromosome and a plasmid.
22. The engineered cyanobacterium of claim 12 , wherein the activity of alcohol dehydrogenase is varied by controlling the level of a co-factor required by alcohol dehydrogenase.
23. The engineered cyanobacterium of claim 15 , wherein said cyanobacterium is a thermophilic cyanobacterium.
24. The engineered cyanobacterium of claim 12 , wherein said recombinant alcohol dehydrogenase nucleic acid sequence encodes a Moorella alcohol dehydrogenase.