Photosynthetic production of glycerol by a recombinant cyanobacterium.

•Recombinant Synechocystis harboring phosphoglycerol phosphatase produces glycerol.•Glycerol is produced at high levels.•Wild-type Synechocystis produces low amounts of glycerol under salt stress.•Glycerol production through the heterologous phosphatase and through salt stress is cumulative.•A sustainable route to glycerol production is provided that does not require arable land.