Figure 1: Metabolic pathways for PHA production.
For the production of PHA in cyanobacteria, the genes, phaA, phaB and phaC were introduced. The condensation reaction of two acetyl-CoA compounds to form acetoacetyl-CoA by PhaA was hypothesized to be thermodynamically unfavorable in cyanobacteria under photosynthetic conditions. Therefore, PhaA was replaced by NphT7 that catalyzes the irreversible condensation of acetyl-CoA and malonyl-CoA to give acetoacetyl-CoA.
Figure 2: Microscope image shows the likely accumulation of PHA in genetically modified cyanobacteria.
Upper left: Image of cells after staining with nile-red pigment that shows lipid and polymer inclusions.
Upper right: Image of cyanobacterial cells.
Bottom: Merged image of upper two images. It shows that PHA is accumulating in cyanobacterias cells.