Increased bioproduction of glycogen, lipids, and poly(3-hydroxybutyrate) under partial supply of nitrogen and phosphorus by photoautotrophic cyanobacterium Synechocystis sp. PCC 6803

Under an adequate supply of nitrogen (N) and phosphorus (P), the cyanobacterium Synechocystis sp. PCC 6803 produced a high biomass yield but with a low storage level of glycogen and poly(3-hydroxybutyrate) (PHB). In contrast, deprivation of N or P stimulated accumulation of glycogen and PHB, but reduced biomass yield. In addition, deprivation of N or P had no apparent effect on total lipid accumulation. Here, we examined how partial supply of N or P has effects on the biomass yield and production of glycogen, PHB, and lipids. The N or P supply in the culture media was orderly decreased from 100% (set according to the standard BG11 medium) to 50, 35, 20, 10, and 0%. A 100% supply of both N and P produced biomass of up to 1.4 g L-1, while a 35-50% N supply slightly reduced the biomass to 1.2-1.3 g L-1, and no apparent change in the biomass was detected under a 20-50% P supply. A maximum glycogen accumulation of 51.8% (w/w dry weight; DW) was obtained under 20% P supply, while the maximum PHB storage of 6.3% (w/w DW) was obtained with 10% P supply. Lipid accumulation peaked at 12.7% (w/w DW) under 0% P supply. The maximal co-production of these three bioproducts was obtained under 20% P supply at 765 mg L-1 which is the sum of 72 mg L-1 PHB (corresponding to 5.1% w/w DW PHB), 618 mg L-1 glycogen (43.8% w/w DW glycogen), and 75 mg L-1 lipid (5.3% w/w DW lipid) from the total biomass production of 1.4 g L-1. The glycogen production (618 mg L-1) was higher than those previously reported for Synechocystis. The results indicated that a proper adjustment of initial N and P supplies in the culture is crucial for maximal production of these three bioproducts by Synechocystis.