The cellular PHB content was determined in 137 strains of cyanobacteria representing 88 species in 26 genera under six photoautotrophic nutrient conditions. One hundred and thirty-four strains were PHB producers. The PHB contents of these 134 strains were subtle under normal growth condition, but were significantly increased in 63 strains under nitrogen deprivation (-N), a higher frequency than with phosphate and/or potassium and all-nutrient deprivation. A high PHB accumulation was not associated with any particular evolutionary groups, but was strain specific. The filamentous Calothrix scytonemicola TISTR 8095 produced 356.5 +/- 63.4 mg/L PHB under-N from a biomass of 1396.6 +/- 66.1 mg/L, giving a PHB content of 25.4 +/- 3.5% (w/w dry weight). This PHB productivity is equivalent to the CO2 consumption of 729.2 +/- 129.8 mg/L. The maximum energy conversion from solar energy to PHB obtained by C. scytonemicola TISTR 8095 was 1.42 +/- 0.30%. (C) 2016 Elsevier Ltd. All rights reserved.