Production of 1,2‐propanediol in photoautotrophic Synechocystis is linked to glycogen turn‐over

We utilized a photoautotrophic organism to synthesize 1,2‐propanediol from carbon dioxide and water fueled by light. A synthetic pathway comprising mgsA (methylglyoxal synthase), yqhD (aldehyde reductase), and adh (alcohol dehydrogenase) was inserted into Synechocystis sp. PCC6803 to convert dihydroxyacetone phosphate to methylglyoxal, which is subsequently reduced to acetol and then to 1,2‐propanediol. 1,2‐propanediol could be successfully produced by Synechocystis, at an approximate rate of 55 μmol h^?1 g_CDW^?1. Surprisingly, maximal productivity was observed in the stationary phase. The production of 1,2‐propanediol was clearly coupled to the turn‐over of intracellular glycogen. Upon depletion of the glycogen pool, product formation stopped. Reducing the carbon flux to glycogen significantly decreased final product titers. Optimization of cultivation conditions allowed final product titers of almost 1 g L^?1 (12 mM), which belongs to the highest values published so far for photoautotrophic production of this compound.