Selection of ADH in genetically modified cyanobacteria for the production of ethanol
The present invention discloses genetically-modified cyanobacteria with ethanol-production capabilities enhanced over the currently-reported art, and methods of making such cyanobacteria. The invention provides a genetically modified photoautotrophic, ethanol producing host cell comprising an overexpressed pyruvate decarboxylase enzyme converting pyruvate to acetaldehyde and an overexpressed Zn2+ dependent alcohol dehydrogenase enzyme converting acetaldehyde to ethanol.
1. A genetically modified cyanobacteria cell comprising:
an overexpressed pyruvate decarboxylase enzyme converting pyruvate to acetaldehyde, and
a Zn2+ dependent alcohol dehydrogenase enzyme Synechocystis Adh, wherein the Zn2+-dependent alcohol dehydrogenase enzyme is overexpressed.
2. The cyanobacteria cell of claim 1 , wherein overexpression of the Zn2+-dependent alcohol dehydrogenase enzyme is controlled by an inducible promoter.
3. The cyanobacteria cell of claim 2 , wherein overexpression of the Zn2+-dependent alcohol dehydrogenase enzyme is integrated into the genome.
4. The genetically modified cyanobacteria cell of claim 1 , wherein the overexpressed dehydrogenase enzyme converts acetaldehyde into ethanol.
5. The cyanobacteria cell of claim 1 , wherein the ethanol production is at a rate of at least 0.0017% EtOH (v/v) per OD1 per day.
6. The cyanobacteria cell of claim 1 , wherein the cyanobacteria cell is Synechocystis sp. PCC 6803.
7. A genetically modified cyanobacteria cell comprising:
an overexpressed pyruvate decarboxylase enzyme converting pyruvate to acetaldehyde, and
an overexpressed Zn2+ dependent alcohol dehydrogenase enzyme derived from Synechocystis (SEQ ID 16) converting acetaldehyde to ethanol, wherein the molecular ratio of acetaldehyde to ethanol in a gas phase over a culture comprising the cyanobacteria cell is lower than 0.101.
8. The cyanobacteria cell of claim 7 , wherein the ethanol production is at a rate of at least 0.0017% EtOH (v/v) per OD1 per day.